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Computed Tomography-Guided Drainage
With developments in cross-sectional imaging, there have been major advances in technical materials enabling interventional radiologists to perform procedures previously considered impossible. Before computed tomography (CT), percutaneous abscess drainage (PAD) was occasionally performed when abscesses were so large they could be palpated, visible on fluoroscopy by displacement of bowel, or superficially located and visible by ultrasound (US). Since the first CT-guided percutaneous aspiration and drainage procedure, which was performed in 1975 and reported in 1976 by Haaga, use of this technique has expanded rapidly.
CT has been especially useful because it has a high accuracy for detecting abscesses and allows accurate determination of the anatomic location and extent of the lesion. Because CT is not impeded by gas or bone, any involvement of peritoneal spaces or anatomic areas can be delineated clearly. This information is necessary if one is to determine whether an abscess can be drained by a percutaneous method. Although there was some controversy in the early literature concerning the merits of different guidance systems for drainage, there now seems to be a consensus that CT guidance is the best method available.
Primary and postoperative abscesses and fluid collections in nearly every organ system have been successfully treated by percutaneous means. PAD has become the treatment of choice for a wide variety of fluid collections, and this attests to its advantages over the alternative of surgical drainage by offering precise noninvasive localization of fluid collections, minimally invasive therapeutic techniques, and avoidance of general anesthesia in most cases. This has resulted in reduced morbidity and mortality and has helped reduce length of hospital stay and hospital costs compared with open surgical drainage. There has been a transition from open surgical drainage to PAD over the last 30 years, except in the most difficult or inaccessible cases.
Results vary according to the complexity of the abscess. Although complications are relatively uncommon, they may be serious, even life threatening. Close communication and strategy between the surgeon and interventional radiologist provide synergy that ultimately benefits the patient.
Perspectives on Abscess Drainages
In the past 3 decades, percutaneous drainage of primary and postoperative abscesses and fluid collections has had a profound effect on the management of the critically ill patient population. The benefits of improved detection and localization of abscess have been documented by Deveney and coworkers, who showed conclusively that the improved localization and intensive care methods have resulted in a greater percentage of drainage success and decreased mortality resulting from organ failure. These authors studied two 5-year periods (1973-1978 and 1981-1986) in a veteran population. The population included patients treated either surgically or percutaneously. The mortality of the two groups was 39% from 1973 to 1978 and 21% from 1981 to 1986. The successful initial drainage was 55% in the earlier group compared with 74% in the latter group. Organ failure rate decreased from 52% to 23%. The surgical success rate was 76% compared with the percutaneous success rate of 72%. The authors concluded that accurate localization and early drainage are the most important factors and that there is no difference in outcome between the surgical and percutaneous methods.
Despite the lack of randomized studies comparing percutaneous to surgical drainage, many studies have been conducted to retrospectively compare the results of percutaneous drainage with the results of surgical drainage in patients with intraabdominal abscesses. Their findings suggest that percutaneous drainage of an abscess can be performed as safely as surgical drainage. With a broad perspective toward drainage, the intent of interventional percutaneous procedures is at least to duplicate the treatment result established by surgeons. The benefit of percutaneous procedures lies in their simplicity, lower complication rates, and presumably lower overall expense. The general view is increasing that PAD is a safe and effective alternative to surgical drainage. Percutaneous drainage can be effective in the management of complex abscesses, including multiple abscesses, ones associated with fistula, and splenic abscesses.
Patient Selection
In recent years the indication for percutaneous methods has expanded significantly. Unlike most new techniques and procedures in which there is an initial period of enthusiasm followed by either moderation or a restriction of the method, percutaneous drainage guided by CT has continued to expand its role. Accumulated experience and refined techniques have expanded the indications for image-guided abscess drainage to permit drainage of complicated abscesses. Examples of such collections are gallbladder infection, pancreatic pseudocysts and abscesses, lymphoceles, and mediastinal and lung abscesses. The prerequisite for percutaneous drainage is an abnormal fluid collection and one of the following: suspicion that the fluid is infected, need for fluid characterization, or suspicion that the collection is producing symptoms to warrant drainage.
To maintain a proper clinical perspective, it is important that the appropriate patients be selected for curative or palliative PAD procedures and for surgical procedures. Simplistically one could try PAD for palliation in every patient, but it is not logical to expand its use for patients with certain surgical problems. On a practical level, although the role and the indications for percutaneous procedures have expanded greatly, there are still clear indications for surgical drainages.
Although there are few contraindications to most imaging-guided fluid aspirations and drainages, one important contraindication is an uncooperative patient. Relative contraindications include patients with abnormal clotting parameters: an INR (international normalized ratio) of greater than 2, an elevated prothrombin time 3 seconds or more above control, a partial thromboplastin time 6 seconds or more above control, or a platelet count less than 50,000/mm 3 . These abnormalities can usually be corrected with appropriate blood products. If a patient is febrile and an infected collection is suspected, we prefer that the patient have at least one dose of intravenous (IV) broad-spectrum antibiotics prior to the procedure. One dose of antibiotics usually does not alter the results of the specimen culture.
The imaging appearance of the abscess indicates how easily an abscess might be drained. Abscesses that are of low density and clearly defined, without septations or not involving numerous peritoneal spaces, are easily drained. The results with septated abscess have varied; some drain well, and others do not. The most plausible explanation is that fibrin septa in such cavities may be complete or incomplete. When they are complete, drainage is poor, and when they communicate and are incomplete, curative drainage can occur. We have studied the use of fibrinolytic agents in the former cases and have found them effective for improving drainage (see “ Fibrinolytic Agents ,” later). Also, the multiplicity of abscess is no longer considered a contraindication to percutaneous drainage, but multiple catheters in each site may be required for optimal drainage.
For the anatomic pathways, we still prefer a clear pathway into the abscess cavity without traversing an uninvolved space or organ. A routine penetration through an uninvolved organ is inappropriate because of possible seeding of pyogenic organisms into the organ, as well as possible injury to the otherwise uninvolved organ. Although with the potent antibiotics of today most such procedures seem feasible, the success and complication rate will favor avoidance of uninvolved organs and spaces. There are several techniques that can be used to create a safe window for percutaneous access, including changing patient position and instillation of air or saline through the access needle ( Fig. 68-1 ).
Viscosity or thickness of the purulent material in the abscess affects drainage success. If the entire cavity can be evacuated easily after aspiration, percutaneous drainage probably would work. If the material appears to be viscous, techniques should be adjusted appropriately (i.e., special attention given to catheter size, catheter placement, and use of an appropriate irrigant; see “ Clinical Management of Catheters ,” later).
The appropriateness of percutaneous drainages for abscess associated with entities requiring surgical treatment is an area of significant controversy. One must weigh the palliative benefits of PAD against the final curative benefits of surgery. On the other hand, the use of PAD for complex abscesses may offer significant therapeutic benefits and palliation by draining most of the infected fluid, allowing the patient to undergo surgery in a more stable condition. This approach for gaining time has been applied successfully in patients with enteric abscesses, appendicitis, Crohn's disease, diverticulitis, and cholecystitis. PAD has converted emergency surgery into elective surgery and has increased the possibility of a successful one-stage surgical procedure in recent years. The success of conservative diverticular disease management including PAD has led some investigators to argue against obligatory elective surgery.
Patient preparation requires evaluation and normalization of coagulation status, administration of periprocedural, culture-specific, or broad-spectrum antibiotics, and evaluation of the patient for tolerance of conscious sedation. Procedures are performed with IV conscious sedation and local anesthesia. Conscious sedation is critical to reduce patient pain and anxiety, increase patient ease and comfort, and thereby decrease the risk of complications. In patients with an inability to tolerate conscious sedation owing to pain, cardiopulmonary instability, or allergies to local anesthetic agents, general anesthesia may be required. For some patients, the procedure may be performed with only local anesthetic because the risk of sedation or anesthesia may be greater than the risk of the procedure.
There is a spectrum of complexity for intraabdominal abscess. Examples of more complex situations include multiple abscesses, abscess due to Crohn's disease, pancreatic abscess, drainage route that traverses bowel or pleura, infected hematoma, or infected tumor. Although some authors have reported curative or partially successful PAD in patients with these complex pathologies, one should expect that these cases are associated with lower success rates, higher rates of complications, technical difficulties, longer periods of time for drainage, and increased chance of recurrence. Decision regarding percutaneous versus surgical drainage of complex collections should be made in concert with other services involved in the patient's care.
Indications for Surgery
Some abscesses are difficult to percutaneously drain and may be better suited for surgical drainage. This group consists of fungal abscesses, infected hematomas, echinococcal disease, most pancreatic abscesses, particularly infected necrotic pancreatitis, and failed percutaneous drainage. Patients with fungal abscesses often require surgical drainage because there is extensive tissue invasion, necrosis, and mycotic plaque formation within the wall of the cavity. Our experience shows that surgical drainage or resection is best for adequate débridement in these patients.
Infected hematomas do not drain well because of the extensive amount of fibrin deposition and the protective effects of fibrin on bacteria. As shown from our early experience and from reports in the literature, such hematomas have uniformly failed by percutaneous drainage. In our more recent experience, fibrinolytic agents used as a catheter irrigant can improve the drainage of infected hematomas.
Echinococcal disease requires a special approach to prevent spread of the daughter cysts into the peritoneum or other areas. The issues related to anaphylaxis are essentially minimal with appropriate technique, and many authors have now reported on the technique of percutaneous drainage (see “ Echinococcal Drainage ,” later).
Unless the interventionalist practices in an endemic area, however, it is unlikely that he or she would develop sufficient expertise to manage echinococcal disease well. In nonendemic areas, echinococcal disease may best be treated by the surgical method.
Finally, for patients who have had a failed percutaneous procedure, surgical drainage is appropriate. Because of the difference in philosophy among surgeons, radiologists, and institutions, the definition of a failed procedure can be determined only at the local level and not in this text.
Imaging Guidance and Access
The most important step in percutaneous drainage procedures is selection of the access route and imaging modality for guidance of needle and catheter insertion. Whenever possible, guidance with US should be considered because it allows real-time monitoring of manipulations and no radiation to the patient. Seemingly inaccessible pelvic fluid collections may be approached with US using a transvaginal or transrectal route. These techniques will be discussed in the pelvic abscess section.
In general the shortest distance between the skin and the collection without interposing organ or vessel is chosen for needle entry and catheter insertion. Selection of the skin entry site is based on previous diagnostic studies and anatomic considerations. The preselected pathway is confirmed by immediate limited preprocedure CT study. A wide area is sterilized and local anesthesia is applied to the skin and underlying soft tissues where the needle and catheter will be inserted.
There is still a debate about which is better, aspiration alone with and without intermittent aspiration or continuous catheter drainage. Some authors believe that aspiration and lavage of the abscess is as effective as more conventional treatment of prolonged catheter drainage. They believe that more manipulation of instruments in the abscess cavity may increase the risk of septicemia. Other advantages of this treatment method include less invasiveness, lower cost, and no need for follow-up catheter care. Rae and colleagues performed percutaneous aspiration alone on 25 patients with hepatic abscesses smaller than 5 cm and had a 100% cure rate. Zarem and Hadzic had 100% success rate for US-guided aspiration of small liver abscesses. They also concluded that continuous catheter drainage was more efficient than intermittent aspiration for liver abscess bigger than 5 cm. Giorgio et al. reported a 98% cure rate of 115 patients who suffered from liver abscess and were treated by US-guided needle aspiration alone.
On the other hand, many authors believe that continuous percutaneous catheter drainage is more efficient than intermittent percutaneous needle aspiration. Catheter drainage is also reported to be more efficient for large abscesses (diameter > 5 cm) and multiloculated abscesses.
General Technique for Aspiration Treatment
Selection of patients for aspiration treatment is based on the characteristics of the abscess. We use this technique when an abscess is too small or inaccessible for catheter drainage. Preprocedure steps are identical to other procedures relative to review of history, medications, imaging, and patient consent.
Needle aspiration of the abscess is performed using similar guidelines as described later under “General Technique and Steps for Catheter Drainage.” We typically use one of the commercially available trocar-based catheter needles to access the collection, such as a Yueh Centesis Catheter Needle (Cook Medical) or a One-Step Centesis Catheter (Merit Medical), which has a 5-French (F) catheter over a 19-gauge needle. Such access needles are preferred because purulent material may be thick and the multiholed 5F catheters are more reliable for recovering a sample than a simple hollow needle. In addition, a standard 0.035-inch guidewire can then be placed through the 5F catheter into the abscess for subsequent catheter insertion using the Seldinger technique.
On recovery of the purulent material, we perform aspiration of purulent contents and sometimes injection of a small dose of antibiotics. The antibiotic chosen should be the one selected from cultures and sensitivities (if available from fluid or blood cultures). The amount of antibiotics injected is equivalent to a nondiluted single intramuscular or IV dose. That amount of drug is deducted from the daily limit stipulated by the manufacturer and approved by the U.S. Food and Drug Administration (FDA). It also is important to pay attention to the volume required, because one must not inject volumes too large for the cavity. For typical pyogens, the volume is not an issue when routine broad-spectrum antibiotics are used. With fungal abscesses, the volume of the dilute drug might be too high, so the dosage needs to be reduced.
General Technique and Steps for Catheter Drainage
The technique of abscess drainage can be divided into the following steps: (1) abscess detection, (2) preprocedure patient workup, (3) choice of the guidance modality, (4) trajectory planning, (5) diagnostic aspiration, (6) catheter selection and insertion.
Abscess Detection
If an abscess has been detected by magnetic resonance imaging (MRI), radioisotope-tagged white blood cells (WBCs), or US, a CT scan should be performed to determine the complete extent of the abscess. The geographic location and degree of involvement are essential factors in choosing the trajectory, determining the number of catheters required, and anticipating possible difficulties. An abscess can be detected in selected cases by any modality, but CT plays the most critical role. CT is the preferred examination because it is the most accurate of all imaging systems for abscess detection. Not only can CT confirm or exclude the presence of drainable fluid, it can also diagnose the causative or associated problem. CT can provide valuable information about diverticulitis, tumors, appendicitis, fistulas, infarcts, cellulitis, phlegmons, inflammatory bowel disease, bowel obstructions, or other problems.
Preprocedure History, Review of Images, Planning, and Informed Consent
Preprocedure steps include physical examination, clinical and medication history, and review of all imaging and clinical data. Medication history is especially important to determine if any anticoagulants are taken (either prescribed or over the counter [OTC]). Laboratory studies including complete blood counts and coagulation values are reviewed. After complete patient interview and discussion of the indications, procedure techniques, expected outcomes, possible complications, and follow-up expectations, an appropriate witnessed informed consent is obtained.
Imaging Preferences
An appropriate choice of imaging modality for guidance is a critical step because it provides information regarding feasibility, appropriate technique, and associated risks for the purposes of informed consent and procedural planning. US is becoming increasingly popular as interventionalists become more experienced with this modality. However, CT is the preferred modality to identify the extent of abscesses and plan the route of access; distinction of the fluid collection from the adjacent normal structures can be exquisitely enhanced by the administration of oral and IV contrast agents. Air is accurately imaged and localized. Adjacent anatomy and virtually all instruments can be visualized without difficulty. CT is also advantageous for guiding drainage, particularly in cases in which collections are small and deep, in close proximity to vital structures, or located in regions that are difficult to assess. In addition, CT fluoroscopy promises to increase accuracy and decrease procedure time.
Target and Trajectory Determination
Trajectory planning is best accomplished by CT, regardless of the imaging modality chosen for guidance. Although as most authors agree, it is best to choose the shortest pathway, it is also optimal to avoid uninvolved organs and noncontiguous peritoneal spaces. For example, common spaces where abscesses can form in the abdomen are the right subphrenic, left subphrenic, and lesser sac. To plan the trajectory in these areas, it is crucial to understand and appreciate the spaces as they relate to the diaphragm and rib cage ( Fig. 68-2 ).
Several points should be made concerning the configuration and nature of the abscess collection. If an abscess collection is long, the trajectory of the puncture should be planned so that the catheter lies throughout the length of the cavity when it is inserted. Two approaches may be used. First, one can choose an entrance site at the upper or lower end of the cavity so that the catheter traverses the entire length or width. The alternative is to make two punctures at the center point, one directed cephalad and one directed caudad, to permit positioning of a catheter at the top and bottom of the cavity (see “ Catheter Selection and Insertion Method ”). If such an abscess is elongated in a traverse direction, catheters should be similarly placed in that transverse plane. If multiple septations are seen within a cavity, it is reasonable to plan the trajectory so that the maximum number of cavities would be traversed.
Although the best surgical results are obtained if an extraperitoneal approach is used, this is not true with percutaneous procedures. Neither we nor other authors have found any indications that a peritoneal approach differs in outcome from an extraperitoneal approach with percutaneous drainage. With percutaneous drainage of peritoneal abscesses, the high-pressure abscess evacuates through the catheter and not into the peritoneum, because the margins of the peritoneum around the abscess are likely fused from inflammation. Drainage of the liver is different and requires a cuff of normal liver (see “ Approaches to Specific Abscess Sites ”).
Diagnostic Aspiration
Patient vital signs and electrocardiographic (ECG) monitoring with automated devices and local anesthetic and sedation administration are the same as used for other sites. Sedation is administered as needed. Most authors use short-acting drugs such as midazolam and fentanyl (or both) as needed. Local anesthesia is administered.
Before catheter or trocar placement, a diagnostic aspiration is performed to confirm the presence of an abscess. We typically use a 5F Yueh needle to perform diagnostic aspiration for two reasons. First, a larger needle permits aspiration of even the thickest purulent material. Second, if at the time of aspiration the fluid appears purulent, the sheath permits insertion of an angiographic wire and catheter without a second puncture.
The actual puncture and placement of the needle are performed in the same manner as any other needle procedure. We take two steps to minimize the risk of contamination along the pathway during the subsequent steps of catheter insertion. First, when draining abscesses in the liver, we choose the path to include a “cuff” of normal parenchyma to lessen the chance of tearing the thin wall of an abscess. We try to avoid traversing normal spleen or kidney while draining splenic or renal abscesses. Second, at the time the puncture is made, we aspirate a sufficient amount of material to lessen the “back pressure” to minimize the chance of local spillage. There is a reported case of spillage into the peritoneum that produced peritonitis and a case of dissemination into the subphrenic area reported by Johnson and coworkers. One must always strive for meticulous technique, but if spillage of purulent material occurs, placement of a second catheter at the site would prevent further problems.
If the aspirated material is not obviously purulent, then one can decide among three different management options: (1) place a catheter, (2) aspirate the entire collection, or (3) aspirate a small diagnostic sample and send it to the laboratory for evaluation. There are advantages to each of these options. We often perform the first option of placing a catheter, particularly if the collection is in a difficult location to access. If the cultures are negative, the catheter can be removed in a day or two. With current antibiotics, the chances of a sterile collection getting a secondary infection from the catheter are low. If the collection is small and simple, the entire collection can be aspirated and thus completely resolve. If the collection is septated and easy to access, then the third option of a small diagnostic aspirate can be performed. In the event that a repeat puncture and drainage might be required, we try not to aspirate the fluid collection “dry”; if such a collection is aspirated dry, there would be no well-defined lesion to target should a drainage be required later. This third option is very conservative and may be considered in such collections in patients who are immunocompromised. Extracted fluid may be characteristic for collections other than abscess. Creatinine is elevated in urinomas; the presence of lymphocytes and fat globules signifies lymphoceles; amylase characterizes pancreatic pseudocysts; and bilirubin is diagnostic for bile collections. Seromas typically yield clear yellowish fluid. In cancer patients with a possible necrotic tumor vs. abscess, a cytologic sample should be sent to determine if there is a necrotic neoplasm or secondarily infected tumor giving toxic symptoms similar to abscesses.
Catheter Selection and Insertion Method
Assessment of the type of fluid to be drained (e.g., pus, bile, lymph, urine, blood) and its characteristics (e.g., clear, particulate, viscous, clot filled) are used to select the drainage catheter size and type. Generally a 10F to 14F catheter with multiple side holes can effectively drain thick, purulent material; similar but smaller catheters (6F or 8F) may be used to drain collections of nonviscous fluid such as that in cysts or seromas and uninfected effusions. The size of the catheters and the size of the pigtail shape to be used should be matched to the size of the abscess cavity so that the entire curved end is in the cavity. It is important to use the largest catheter possible from the beginning; if the procedure becomes technically difficult, one can settle for almost any size of catheter and upgrade it later.
It is important not to have holes outside the cavity. If holes are outside, leakage into a sterile space or organ can occur. The catheter is secured to the skin with an adhesive device or suture and sterilely dressed. In patients at high risk for accidental catheter removal, the catheter should be secured directly to the skin with suture. Catheter position should be noted and marked if necessary to detect accidental removal. The catheter should be drained to a suction bulb. Dressings can be changed during rounds or by the nursing staff.
Two types of techniques can be used to place drainage catheters: Seldinger method and single-step catheters. Either may be used depending on the specific nature of each case. The Seldinger method is well suited to all abscesses regardless of the size or location; even the most difficult deep abscess can be drained with this method. We use the single-step catheters with larger superficial abscesses.
Seldinger Method.
Seldinger technique is the preferred method for placement of catheters in most collections, including small collections and those that are difficult to assess. Seldinger technique carries the advantage of verification of successful access into the collection and successful avoidance of adjacent structures prior to the creation of a large-bore tract. The principal disadvantage of this technique is potential risk of loss of access and cross-contamination while exchanging dilators, during which abscess contents have the potential to spread to the bloodstream or adjacent spaces.
Access is gained using a 5F Yueh needle (or similar catheter-based needle). After the needle has entered the cavity and a sample has been aspirated for culture and to relieve the pressure. A 0.035-inch guidewire is advanced into the cavity. Choice of the guidewire is an individual preference; we prefer a slightly stiffer wire such as a Rosen or an Amplatz so that dilation of the tract and catheter insertion is facilitated. Although some interventionalists are reluctant to use stiff wires, the stiffness prevents kinking of the wire or catheter during the dilation or insertion process. If the abscess is secondary to a local infarction or necrosis of the organ, a softer, more flexible wire may be used. Availability of a portable fluoroscopy device or an attached fluoroscopy unit is helpful to confirm guidewire location. With experience, one can insert the catheter on the CT table, using the topogram as the method for confirming the catheter location or blindly using a sense of “feel.” Under direct visualization, serial fascial dilation over the guidewire is performed to accommodate the size of the drainage catheter. A locking-loop pigtail catheter with a metal or plastic stiffener is advanced over the wire into the collection. The stiffener and wire are removed and the catheter is locked.
Single-Stick or Trocar Technique.
Some practitioners use the single-step trocar technique routinely, but one should be cautious when using this technique for small or critically located abscesses (see “ Drainage Errors ”). We use this technique with US-guided transvaginal, transrectal, and selected cholecystostomy catheter placements and CT-guided drainage of larger more superficial collections in our institution. This technique facilitates rapid drainage of the collection and minimal potential for spreading the infection owing to the absence of serial fascial dilation. However, the long trocar associated with the catheters may not fit into the CT gantry, particularly with larger patients. The trocar-based catheter does not penetrate the soft tissues as easily as a 5F Yueh needle. These two factors limit their use in deep smaller lesions that might be close to critical structures. Another principal disadvantage is the direct advancement of a large-bore catheter and sharp stylet, which can have serious consequences in cases of inadvertent nontarget access.
In this technique, direct CT guidance is used to access the fluid collection by advancing the combination of a drainage catheter loaded with a metal stiffening cannula and a sharp inner stylet. The distance between the skin and the collection (measured by US or CT) is marked on the catheter shaft. The trocar-based catheter is then advanced into the collection. Catheter advancement can be monitored by CT, US, or fluoroscopy. The stylet is removed and fluid is aspirated to confirm catheter position in the collection.
Final positioning of the catheter is important. To lessen the chance of dislodgment, it should be placed into the most dependent part of the abscess and not superficially (see “ Drainage Errors ”). If the cavity is long, the catheter is positioned through the length of the cavity, or two catheters are inserted to prevent regional loculations and enhance complete drainage. We make sure none of the holes in the catheter are outside the cavity. After the catheter is positioned, we gently evacuate most of the purulent material from the cavity and irrigate it with saline. If the fluid becomes blood tinged, irrigation should be discontinued.
When loculations are present, the catheter should not be overirrigated or overmanipulated to prevent bacteremia. Some authors have recommended the use of a wire at this point to disrupt any septations or adhesions, but this may be imprudent. Using a wire may traumatize the wall and cause a significant bacteremia or hemorrhage from the granulation tissue. We favor use of fibrinolytic irrigations to treat such cases (see “ Catheter Irrigation and Fibrinolytics ”).
Catheters can be sutured to the skin with 2.0 or 3.0 Prolene or other nonabsorbable material for external fixation. There are several adhesive retention devices that may be used in lieu of a suture. Large-bore catheters placed in the chest or abdomen also may require skin sutures to prevent dislodgment.
Clinical Management of Catheters
When the catheter is in place, a few guidelines must be followed to ensure a successful drainage. In general, catheters are connected to a collection bag for drainage by gravity. This setup is more effective when the fluid drained is nonviscous. Collections with viscous fluid or particulate material need catheter irrigation and may require intermittent low wall suction. High suction may pull debris and tissue into the catheter holes and impair drainage. Active suction should be used for high-output collections (e.g., gastrointestinal [GI] or urinary tract fistula) to keep the cavity dry and promote healing. The catheter is irrigated to maintain patency. Without irrigation, catheters may occlude regardless of their size. Proper catheter irrigation involves the following steps: placement of a syringe in the stopcock and aspiration of residual fluid, injection of 5 to 10 mL of normal saline, aspiration of the irrigant, and reflushing the catheter with 5 mL of normal saline.
Patients should be followed on a daily basis for catheter output, skin access site leakage or infection, and laboratory and clinical signs of complications or failure of drainage. When a drainage procedure has gone well, the patient responds quickly and shows dramatic clinical improvement. In such patients, the fever abates and the WBC count decreases. The progress of the drainage also can be assessed by following the sequential changes in the appearance of the fluid. Initially the material is cloudy and turbid; it then changes to a serosanguineous appearance, and finally it changes to a clear serous material. Cultures of the fluid also change sequentially so that when the abscess has resolved, drainage fluid is sterile. After this clinical response and the changes in character of the material, the catheter can be removed.
If the patient does not respond as expected, the fluid drainage is scant, purulent fluid does not evolve as expected, or the drainage begins to show bile or enteric material, repeat imaging is indicated. Persistent large volume of fluid output, output of tube feeds, or output of fecal matter may indicate a fistulous connection. Fistulas usually are not apparent on initial postprocedure scans because the small fistulas can be sealed by inflammatory edema in the area, which temporarily occludes the fistula. As healing begins and edema reduces, the fistula may open up and change the appearance of the drainage material or the appearance on CT. A repeat CT scan should be performed to evaluate the abscess to determine if a fistula is present (shows large amount of air), if portions of the cavity are incompletely drained, or if additional cavities have developed. Evaluation of the catheter status is important to detect any displacement or kinking. A sinogram under fluoroscopy can document the presence of a fistula ( Fig. 68-3 ). Repeat puncture and catheter insertion and upsizing or repositioning of the catheter may be necessary.
Catheter Irrigation and Fibrinolytics
If the material being drained is thin and no definite septations are noted on imaging studies, we recommend flushing the catheter with saline. Saline in the amount of 10 to 15 mL should be injected every 6 to 8 hours to keep the catheter lumen clear. If the material being drained is thick or there are septations in the abscess, fibrinolytic agents may be used when the material is thick or septations are present within the abscess. Tissue plasminogen activator (tPA) can be injected into the abscess cavity every 8 to 12 hours for 3 to 4 days. Fibrinolytic agents such as tPA change the substrate plasminogen to the active fibrinolytic agent plasmin. There is no reason to suspect that its activity should be any different than urokinase. If one reviews the table of information from the urokinase study ( Table 68-1 ), it can be seen that urokinase improved the clinical factors of the patient and shortened the drainage time and hospital stay.
TABLE 68-1
Results of Student's Test for Length of Stay, Treatment Cost, Febrile Course, Days of Elevated WBC Count, and Days of Drainage
From Haaga JR, et al: Intracavitary urokinase for enhancement of percutaneous abscess drainage: Phase II trial. AJR Am J Roentgenol 174:1681–1685, 2000.
| Test for | Group | Mean | t | df | P * |
|---|---|---|---|---|---|
| Length of stay (days) | Saline | 29.00 ± 17.2 | 3.56 | 24 | 0.0025 |
| Urokinase | 13.11 ± 9.5 | ||||
| Treatment cost ($) | Saline | 62,102.11 ± 42,844 | 3.49 | 22.3 | 0.0021 |
| Urokinase | 24,178.00 ± 17,871 | ||||
| Febrile course (days) | Saline | 4.00 ± 6.25 | 1.63 | 18.1 | 0.1202 |
| Urokinase | 1.45 ± 1.73 | ||||
| WBC elevation (days) | Saline | 9.12 ± 8.79 | 1.41 | 25.7 | 0.1710 |
| Urokinase | 5.62 ± 5.04 | ||||
| Drainage (days) | Saline | 14.88 ± 20.5 | 1.57 | 17.5 | 0.1361 |
| Urokinase | 6.93 ± 4.2 |
df, degrees of freedom; WBC, white blood cell count.
The amount of urokinase used depends on the size of the cavity, as follows: 0 to 3 cm, 12,500 IU; 5 to 10 cm, 50,000 IU; and greater than 10 cm, 100,000 IU. After the urokinase has been injected, a small amount of saline should be used to clear the catheter of urokinase. The catheter should be clamped for 5 minutes then left to gravity drainage. If tPA is used, the corresponding amount is administered; one should check with the pharmacy or package insert for the amount relative to urokinase. The use of tPA is not approved by the FDA but is legal according to off-label regulations.
The effectiveness and safety of fibrinolytics has been documented by our group in the literature. Park et al. showed that urokinase decreased the viscosity of purulent material more than saline alone did in vitro. The safety of urokinase in vivo was proved by Laborra and colleagues, who showed that intracavitary urokinase produced no systemic effects. A later article by Haaga's group showed considerable benefit for using urokinase compared with saline. This article demonstrated that its use improved treatment of abscesses. Its use produced earlier improvement of clinical parameters and shortened hospital stay ( Table 68-2 ; also see Table 68-1 ).
TABLE 68-2
Effect of Loculation on Length of Stay and Hospital Costs
From Haaga JR, et al: Intracavitary urokinase for enhancement of percutaneous abscess drainage: Phase II trial. AJR Am J Roentgenol 174:1681–1685, 2000.
| Loculation | Test | Group | Mean | t | df | P * |
|---|---|---|---|---|---|---|
| No | Length of stay (days) | Saline | 27.09 ± 17.8 | 2.81 | 11.5 | 0.0168 |
| Urokinase | 11.04 ± 4.72 | |||||
| No | Treatment cost ($) | Saline | 58,023.33 ± 44,075 | 2.81 | 11.8 | 0.0169 |
| Urokinase | 21,567.40 ± 7797 | |||||
| Yes | Length of stay (days) | Saline | 32.50 ± 17 | 2.13 | 9 | 0.0617 |
| Urokinase | 13.20 ± 11.81 | |||||
| Yes | Treatment cost ($) | Saline | 70,259.66 ± 42,981 | 2.97 | 5.3 | 0.031 |
| Urokinase | 17,315.60 ± 6760 |
df, degrees of freedom.
Continuous Irrigation
In some cases when especially thick material is present, placement of several catheters for irrigation may be beneficial. One catheter is used for inflow of saline, and one or more catheters may be used for evacuation of the fluid. In such cases, one should ensure that fluid is moving freely between the catheters so there is no fluid buildup.
Sinograms
Some authors have performed catheter sinograms to follow abscess cavities. Diluted contrast is injected through the catheter slowly and under low pressure. A CT sinogram can show if cavities are undrained and if additional catheters are necessary. The study can be obtained for collections in which a fistula is suspected. During the sinogram, one evaluates whether the catheter placed is still in the correct position and is of adequate size for the evacuation of any residual purulent material. If there is considerable purulent material left, one may choose to increase the size of the catheter. At this time, sequential dilation may be performed safely without bacteremia because the pathogens are fewer as a result of the treatment. If the drainage material is thick or loculations are present, one might institute catheter irrigation with fibrinolytic agents at this time if it was not used initially. With the cavity partially evacuated the contour may change and shift the location of the catheter, requiring adjustment of the position. Repositioning, replacement, or adjustment should be performed as appropriate.
Fluoroscopic sinograms reveal any communication with the bowel or biliary system that should be treated with suction or additional catheters. When performing such sinograms, one should be careful not to inject the catheter and cavity with too large a volume of contrast. Excessive volume may increase the intracavitary pressure sufficiently to cause bacteremia or to rupture a weakened wall of a cavity and produce spillage.
To prevent political conflict with clinical services, it is always helpful to remind clinicians that in many cases a preexisting fistula may be the primary cause of the abscess. The late appearance of a fistula during the drainage process is due to the fact that inflammatory edema in the wall of the abscess occludes a fistula temporarily. At a later time when the inflammation partially resolves, the fistula opens and manifests itself. One should not accept such fistulas as caused by the PAD unless the bowel was clearly crossed during the procedure.
Catheter Removal
The decision to remove the catheter is easy if the course of the drainage (i.e., clinical response including defervescence and resolution of leukocytosis, evolution of fluid changes, and resolution of the fluid cavity on the sonograms) is as expected. Another criterion used for catheter removal is decrease in catheter output to an immeasurable amount (<10 mL/day). When drainage volume decreases to 20 to 30 mL/day, catheter irrigation is discontinued. If catheter output remains below 10 mL/day for more than 24 hours, the catheter is removed unless a pancreatic, intestinal, or urinary fistula is present.
Before removal of a catheter, a final scan can be obtained to ensure that the cavity has closed completely. If this has occurred and there is no continued drainage, the catheter can be removed. An abscess that is completely resolved should show virtually complete obliteration of the cavity (but one may see a small amount of residual fluid and air). A liver abscess may be confusing on follow-up scans. An abscess may be completely drained, but an ill-defined low-density area at the site slightly higher in density than fluid may remain. This represents local fatty change or edema or both, which resolves spontaneously. If a considerable amount of fluid remains, it is best to wait until the cavity has more completely resolved and has been reduced in size by granulation tissue. If a patient is doing well clinically, he or she may be discharged and managed as an outpatient during the time it takes for the cavity to granulate closed.
The patient's antibiotics should be continued for several days after removal of the catheter. Long-term follow-up imaging may be required if the patient has a condition that is likely to recur (i.e., pancreatic pseudocysts, lymphocele, cystic tumors).
Fistulas
GI or biliary fistulas commonly occur with intraabdominal abscesses; some fistulas probably cause abscesses and some are sequelae. Management depends on the amount of flow, whether it is of low or high output. Low-output fistulas (320 mL/day) usually close spontaneously without additional therapy. High-output fistulas require treatment. High suction on the catheter should be maintained and the bowel should be put at rest. This usually means insertion of a nasogastric tube. Hyperalimentation also may be needed for several weeks in some severe cases. Failure of these methods indicates a need for surgery.
Fluid collections may recur if the fistula has not healed by the time the drainage catheter is removed. Sometimes a fistula is seen on sinogram despite minimal drainage from the catheter, because fluid can internally drain through another route. In this situation the catheter is clamped for 1 to 3 days to allow reaccumulation of fluid. If no collection is identified by imaging, the catheter can be removed. Fluid collections associated with fistulas may require prolonged drainage. Persistent low-output drainage can be managed by downsizing the drainage tube and gradually removing it over 3 to 5 days. Presumably this technique allows collapse and closure of the tract as the catheter is pulled out.
Success Rates
Since the introduction and development of PADs, there has been controversy among various groups about the achievable success rate, which overall has varied between 70% and 90%. Successful diagnostic aspiration is defined as aspiration of material sufficient for diagnosis. Curative PAD is complete resolution of infection requiring no further operative intervention. Partial success is either adequate drainage of the abscess with surgery subsequently performed to repair an underlying problem or as temporizing drainage performed to stabilize the patient prior to surgery. Partial success has been reported in 5% to 10% of patients. Failure occurs in 5% to 10% and recurrence in 5% to 10%. These results are similar for both chest and abdominal PAD procedures.
The differences in success rates depend on numerous factors including relative contraindications, complexity of the collections, severity of the underlying medical problems, drainage technique, and catheter selection. Abscesses can be classified into three main groups that are organized by complexity and reflected in success and failure rates. The unilocular and discrete abscess is simplest to drain, and successful PAD has been reported in up to 90% to 95% of cases. More complex abscesses are frequently multilocular with very viscous and purulent contents or contain necrotic tissue; these factors may make complete drainage difficult even with the use of large or multiple catheters. The medium-complexity abscess (i.e., abscesses that have a communication to the GI tract) are cured in 80% to 90% of cases. Associated GI communication may require an operation, but if surgery is performed after PAD, the surgery is simplified because of the noninfected bed. The most complicated collections include intermixed pancreatic abscess/necrosis, infected tumor, and tenacious organized empyemas. The cure rate in these latter situations are no higher than around 80% and may be as low as 30% to 50%.
PAD has also been used for postoperative intraabdominal abscesses with high technical success. Benoist and colleagues investigated the factors prognostic of PAD failure for postoperative intraabdominal abscesses in 73 patients. They found that complex abscesses, including those associated with enteric fistula, were not associated with significantly increased failure rates. Insufficient antibiotic therapy and abscess diameter of less than 5 cm were the only two independent factors predictive of PAD failure in their study. They reported that small abscesses in the failure group required repeat surgery for persistent or recurrent sepsis after removal of the drainage catheter, likely secondary to incomplete drainage. The overall success rate in this study was 85.6% after 1-year follow-up, similar to the previously reported high success rates.
Numerous authors have studied the patient factors that affect the outcome of drainage procedures. Several major determinants have been found, including the status of the immune system, the overall severity of the patient's illness, and underlying medical condition. Lambiase and colleagues reported a large series of patients treated with PAD and noted a significant difference in the outcomes of their patients. They considered the following states as immunocompromised: absolute neutropenia, infection with human immunodeficiency virus, cancer with distant spread, chemotherapy, radiation therapy, lymphoproliferative disorders, diabetes requiring treatment, long-term renal dialysis, splenectomy, and severe alcoholism. They found that with PAD the overall cure rate for immunocompromised patients was 53.4% compared with the normal rate of 72.6% for normal immunocompetent patients in their series.
Many studies have demonstrated that an objective severity-of-illness scoring system is predictive of the patient's prognosis. A widely used system is the APACHE II score, which is prognostic of both mortality and morbidity in patients with intraperitoneal abscesses. Higher APACHE II scores are generally associated with high morbidity regardless of the treatment method. Levison and Zeigler correlated the APACHE II score with drainage techniques and outcome. These authors found that patients with scores less than 15 had a mortality rate of 1.7%, and patients with scores higher than 15 had a mortality rate of 78%. There was no benefit of one method—surgical or percutaneous drainage—over the other.
There are many reasons for the failures reported, including premature withdrawal of the catheter, presence of a GI fistula, pleural contamination, hemorrhage, and the errors of selecting cases, as noted earlier. Lang reported a series of 136 patients with a failure of 29 of 119 attempted curative procedures. With infected pancreatic processes, Lang and colleagues were successful in 11 of 22 cases. In their series, they had 17 patients with identified GI fistulas; 9 resolved spontaneously, and 8 required surgical management. Failure to document the complete obliteration of abscesses by CT resulted in failure in 7 cases. They had 2 cases of hemorrhage associated with inappropriate placement of catheters in areas with phlegmons. The most common misdiagnosis was failure to identify loculated or residual cavities. Premature withdrawal was made in many cases because of the cessation of drainage fluid. The authors recommended that a repeat CT scan be performed before removal of the catheter.
Drainage Errors
Errors associated with abscess drainages have been documented by numerous authors. Perhaps the most common error made is the improper choice of trajectory, which can cause either a portion of the pleura to be crossed when draining a subphrenic abscess or a solid organ to be traversed. Although with today's potent antibiotics, dissemination of an infection is infrequent, it can occur and produce significant difficulty. If an abscess is very large, one can be overly confident and attempt to hasten a procedure by “skipping” some steps, such as using CT localization. In one such patient, one of our experienced physicians used a one-stick catheter without guidance and penetrated the femoral vein. The patient did well after insertion of a vena cava filter to prevent emboli, insertion of a proper drainage catheter, and removal of the offending catheter from the vein.
Removal of some purulent material is important after the initial puncture to relieve the tension of a large abscess. If this is not done, there is a chance that leakage of infected material may spill into the peritoneum during the insertion and manipulation of the wire and catheter.
Relative to placement of the catheter, it is important that the largest catheter possible be inserted, not only to permit rapid drainage of the fluid but also to provide ample diameter should purulent material become inspissated on the inner wall of the catheter. This does not mean a massive catheter is required, but one at least 10F to 12F should be used. Also, the catheter should be placed in the most remote site of the cavity so that loculations do not occur distal to the location of the catheter. Inadvertent or early removal of the catheter can result in recurrence of the abscess. Prior to removing a catheter, we often obtain a CT scan to verify complete resolution of the abscess. Alternatively, if a catheter has been inserted into a sterile fluid collection and it is not removed promptly, a secondary infection of the fluid space can occur.
Finally, if an abscess does not resolve with drainage or enlarges, one should suspect a fungal infection or spontaneous bleeding. It is frequently observed that the infectious agent in an abscess may change based on elimination of sensitive organisms and selection of resistant organisms. Candida species commonly becomes the dominant organism in a patient with multiorganism infection who is treated with broad-spectrum antibiotics selected for bacterial pyogens. In several cases, we have encountered an abscess that appeared to increase in size and developed an elevated density. In such cases, localized bleeding may occur because of the invasion of the local blood vessels; effective percutaneous drainage is typically impossible and surgery is preferred.
Complications
Even the most talented and compulsive interventional radiologist will experience complications of abscess drainage, including complications of sedation, drug-related allergic reactions, cardiopulmonary complications, infectious complications, bleeding, and nontarget access. The overall procedure threshold for all major complications resulting from adult percutaneous abscess and fluid drainage is 10% according to the Society of Interventional Radiology Standards of Practice Committee. Published rates of complications vary widely depending on technique, types of abscess being drained, and various authors' experience. Reported rate of major complications of abscess drainage has been under 5% in most series of patients. Sepsis and bleeding occur in less than 3% of cases. Death is extremely rare. Minor complications, such as secondary wound infection, pneumothorax, discomfort from the catheter, and dislodgment, occur in approximately 5% to 10% of patients.
The most common complication in all series is that of sepsis following catheter insertion. Despite all efforts to localize collections by imaging guidance, transient bacteremia results from spillage of infected contents into the bloodstream in up to 5% of cases. During primary catheter placement, inherent risks include spread of abscess contents to the adjacent spaces or organs, transient bacteremia, and frank sepsis. Spread to adjacent structures or the bloodstream can result from nontarget puncture or prolonged serial fascial dilation. We often use IV contrast injection to improve visualization of vessels, bowel, and other structures before placing the catheter. Another measure to prevent inadvertent spread of infection during fluid drainage is avoidance of nonsterile routes of drainage into potentially sterile collections if possible.
Management of Intrathoracic Fluid Collections
In the thorax, abnormal fluid can accumulate in the pleural space, lung parenchyma, or mediastinum from a variety of etiologies, including infection, malignancy, surgery, and trauma. Each of these entities has a unique set of associated considerations and potential complications. Percutaneous diagnostic aspiration can be performed safely and accurately, and drainage catheters can be placed for treatment of infected or otherwise symptomatic collections. US is the preferred guidance modality for the more superficial and simple fluid collections. CT is opted for deeper, loculated, multiloculated, and more complex collections.
Pleural Fluid Collections
Abnormal fluid in the pleural space is easily accessible by percutaneous methods. The four percutaneous procedures most commonly performed are diagnostic thoracentesis, therapeutic thoracentesis, pleural sclerosis, and empyema drainage. Complicated pleural effusions are fluid collections that require drainage to resolve. Exudate, empyema, and hemothorax are examples of complicated effusions. They are the most common indications for drainage catheter placement. Other indications for drain placement include malignant effusion, recurrent effusions, chylothorax, pneumothorax, hemopneumothorax, and leakage into the pleural space from esophageal or gastric rupture.
Empyema
Empyema is an accumulation of purulent material within the pleural space. Despite the development of new antibiotics, empyema remains a common problem and is associated with mortality rates as high as 40%. Along with antibiotic therapy and treatment of underlying disease, early and complete drainage of infected fluid is essential in the successful management of empyema.
Traditionally empyema has been managed by surgical placement of large (22F-34F) catheters in the pleural space. However, small drainage catheters have successfully been used in the management of empyema. Shankar and colleagues reported a study of 103 patients with empyema, in which 80 patients were successfully treated by placing small (<14F) drainage catheters under US or CT guidance. This result is comparable to those of previous studies in which larger catheters were placed for empyema treatment.
The most recent prospective study by Rahman and colleagues also demonstrated that small (<14F) drainage catheters were as effective as large (>14F) catheters in the management of infected pleural fluid collections. There was no significant difference in clinical outcome in patients with different-sized drainage catheters. In this study, patients with smaller drainage catheters experienced much less pain than those with large catheters, which were mainly placed by blunt dissection.
Pathogenesis and Etiologies.
Infected pleural fluid has developed in association with pulmonary infections, surgery, trauma, foreign bodies, esophageal perforation, or inflammatory processes below the diaphragm. Primary lung infection and postoperative complications are the most common etiologies of empyemas and account for up to 65% of reported cases.
Anaerobic bacteria have replaced gram-positive organisms as the most common cause of infected pleural fluid collections in adults. More than one anaerobic organism is usually cultured from an empyema. Because anaerobes are fastidious and so common, culture specimens should be handled appropriately to ensure positive results. The specimens should be cultured quickly, and they should be exposed to as little air as possible because air may kill the anaerobic organisms. Although there has been a recognizable change in the organisms associated with empyema, management and clinical outcome with treatment have not been altered. Staphylococcus aureus remains the most common organism found in empyemas in children.
There are three stages in the evolution of an empyema, and the stage determines management. The first stage is the exudative stage, in which there is accumulation of sterile free-flowing pleural fluid. The pleural fluid at this time contains rare polymorphonuclear leukocytes (PMNs), a normal glucose level, and a normal pH. The second stage is the fibropurulent stage in which the sterile pleural fluid has become infected with bacteria and the cellularity and protein content in the pleural fluid increase. Fibrin is deposited on the visceral and parietal pleura. As this stage progresses, loculations form, the pleural fluid pH and glucose decrease, and the lactic dehydrogenase (LDH) level and the number of PMNs increase. In the third or organization stage, fibroblasts and capillaries grow into the exudate and form a pleural peel. If untreated, this stage may result in entrapment of adjacent lung or drainage of fluid through the chest wall (empyema necessitatis) or into the lung (bronchopleural fistula). Although the best method of managing an empyema is controversial, early intervention is the key to preventing pleural peel formation and development of an entrapped lung. Once a peel forms, decortication is almost always necessary, although there is evidence that some pleural peels can resolve spontaneously if the underlying empyema is treated satisfactorily.
Diagnosis.
Decubitus radiographs can be a sensitive and inexpensive method to determine if the effusion is free flowing or loculated. This will determine whether intervention is needed and by what modality it should be performed. The visualization of septations on US suggests an exudative process. However, CT allows a more thorough evaluation of the chest. This includes the ability to detect and localize pleural fluid, determine whether it is free flowing or loculated, assess the number of collections, and evaluate the underlying lung parenchyma.
Analysis of the pleural fluid by routine thoracentesis determines the stage of empyema and the most appropriate management. If there is aspiration of gross pus or if the Gram stain is positive, the pleural space should be drained immediately. A positive Gram stain, even if nonpurulent fluid is obtained, is indicative of advanced disease and drainage is recommended. If the pleural fluid is not grossly purulent and does not have microorganisms on the Gram stain, then assessment of the fluid composition can be used to direct management. The most important pleural fluid components to measure are pH, glucose, and LDH levels. When the pleural space becomes infected, the pleural fluid glucose level decreases secondary to glycolysis from PMN phagocytosis and bacterial metabolism. This increase in glucose metabolism results in accumulation of lactic acid and CO 2 , which decreases the pleural fluid pH. The pleural fluid LDH level rise is due to cell lysis. Of these three components, the pleural fluid pH will usually decrease before the glucose level decreases and the LDH level increases. These three parameters are important predictors of whether an effusion will resolve with or without drainage. Many authors use criteria based on the combined pleural fluid data of Sahn and Light. For pleural fluid with a pH below 7.10, glucose below 40 mg/dL, and LDH above 1000 U/L, early drainage is recommended to avoid subsequent development of a complicated multiloculated effusion or a pleural peel. For free-flowing fluid with a pH above 7.30, glucose above 60 mg/dL, and LDH below 1000 U/L, the fluid will probably resolve spontaneously if appropriate antibiotics are given. For fluid with a pH between 7.10 and 7.30, it is recommended that antibiotics be given and the patient be observed closely. If needed, repeat thoracentesis can be performed.
Indications for Chest Tube.
As stated earlier, the primary indication for chest tube placement is to drain an empyema and prevent progression of the pleural process to the organized stage. Although recent radiologic series have demonstrated fairly high success rates with percutaneous drainage, there is still controversy as to whether radiologic or surgical tubes should be used. Davies and coworkers, however, presented cases with chronically infected pleural effusions that were successfully treated by small (12F) ambulatory indwelling pigtail catheters for 8 to 21 months. The authors also stated that small long-term drainage catheters were especially beneficial for patients who were not surgical candidates.
Pierrepoint and colleagues compared the clinical outcome in 24 pediatric patients with empyema who were treated by surgical open thoracotomy with pleural débridement, conventional stiff chest drain catheter, or pigtail drain catheter placement. Pigtail catheters were placed under image guidance and were considerably smaller than conventional stiff drains. Patients who were treated by pigtail catheters or surgical thoracotomy showed better outcomes compared to those with conventional stiff drains. The outcome included shorter drain time, earlier clinical improvement, earlier resolution of fever, and earlier discharge. Pigtail catheter placement was also associated with less pain and discomfort; the authors concluded that pigtail drainage catheters were preferable to thoracotomy.
Indications for imaging-guided pleural catheter placement include failure of surgically placed chest tubes, collection too small for safe surgical tube placement, debilitated patients who are too ill to undergo an operative procedure, and multiple loculated fluid collections. In general, recurrent chronic pleural infection is considered a contraindication for long-term indwelling catheter placement. The treatment of choice therefore has been open surgical drainage of infected fluid.
Percutaneous Technique.
Prior to the procedure, patients should receive appropriate antibiotics. If the pleural fluid is free flowing, a diagnostic thoracentesis can be performed with US guidance. If there is gross pus or a positive Gram stain, a drain can be placed. However, many pleural fluid collections are already loculated when the patients are referred for percutaneous drainage. We prefer to use CT guidance both to perform diagnostic aspiration and for placement of drainage catheters in loculated collections. CT provides optimal visualization of all loculations, differentiates between collapsed lung and pleural fluid, and allows visualization of the needle, guidewire, and catheter during the drainage procedure ( Fig. 68-4 ).
Once the loculated collection is localized, the patient is placed in a position that allows optimal access. A diagnostic thoracentesis is performed. Because CT provides complete visualization of the collection, the trajectory of the needle can be planned such that the entire collection can be traversed. If the collection is located posteriorly, we attempt to use an approach that is as lateral as possible. Using a lateral approach for drainage of a posteriorly located empyema allows the patient to later lie supine without lying on the catheter and potentially kinking it. A direct posterior approach can be used, but the catheter may become kinked when the patient lies down and limit the drainage. Drainage performed with US may be limited to a posterior approach for posteriorly located collections. An important point is to use a more lateral approach in preference to a posterior approach.
For CT-guided drainages, we use a 5F Yueh catheter or equivalent catheter-needle because even very thick purulent fluid can be aspirated with little difficulty. If drainage is desired, a catheter can be placed using the Seldinger technique. We generally use the Seldinger technique to introduce the catheter into the pleural space. Single-step catheters with trocars can be used, but the Seldinger technique provides better control and reduces the chance of injury to the underlying lung. Inadvertent entry of air during dilation of the tract is not a problem, because the collections are usually loculated and the catheter will be connected to a Pleur-evac (Teleflex Medical, Research Triangle Park, NC) and wall suction.
Viscosity of the fluid determines size of the catheter. Most collections can be drained with 8F to 10F catheters. It is sometimes technically difficult to introduce a catheter into the pleural space because the catheter or the guidewire may buckle. Adequate dissection of the subcutaneous tissue along the needle tract and use of a stiff guidewire (Amplatz guidewire, Boston Scientific, Marlborogh, MA) can help prevent this buckling. Occasionally a 12F to 14F catheter will be needed to drain viscous fluid. Insertion of a large catheter can be difficult without fluoroscopic guidance. We rarely use a catheter larger than 14F; instead we instill tPA into the pleural space (see later discussion).
Apparent unilocular collections frequently contain multiple thin septations that cannot be visualized on CT images. These septations become apparent only when a small amount of fluid is aspirated from a catheter positioned in the middle of the collection. Despite being fine and delicate, these thin septations are probably just as responsible for failure of percutaneous drainage as the viscosity of the fluid. If multiple thin septations are present within a fluid collection, it is helpful to have the needle traverse as much of the collection as possible before removing the sharp stylet. The sharp needle point punctures the septations, subsequently allowing a single catheter to drain many of the loculations. Although additional mechanical disruption of the septations can be performed, we prefer to instill tPA to dissolve these septations.
To achieve optimal drainage, it is helpful to have the pigtail portion of the catheter in a dependent position within the fluid. Nephrostomy-type catheters with side holes in the distal pigtail are the type of drainage catheters most frequently used. Catheters with additional side holes more proximal to the pigtail (biliary type) can be used, but care must be taken to ensure that all of the side holes remain within the pleural collection. Once the catheter is placed, it can be sutured to the skin or attached with adhesive fixation devices (Percu-Stay, Derma Sciences, Inc., Princeton, NJ). Continuous low wall suction is used for thoracic collections. Chest drainage catheters are connected to a Pleur-evac connected to wall suction at −20 cm of water. The Pleur-evac is a waterseal device with a fluid collection chamber and a safety mechanism to prevent excessive suction.
The patient is continued on antibiotics tailored to the culture and sensitivity results of the fluid sample. The pleural fluid output is monitored daily. Assuming there is good drainage, the tube position can be checked every 2 to 4 days with chest radiographs. If there are any problems, a repeat CT can be performed to check tube position. Additional drainage tubes can be placed as needed for any separate collections not being drained.
The drainage catheter can be removed when the fluid becomes serous, output decreases to less than 20 mL per 24 hours, the patient is defervesced, and the WBC count is normal. A repeat CT should be performed prior to catheter removal to ensure there are no undrained collections.
When empyema drainage is performed, it is important to work closely with the thoracic surgeon. Not all collections are amenable to percutaneous drainage. Patients who develop a pleural peel or have persistent fevers and elevated WBC counts despite 48 to 72 hours of adequate drainage and appropriate antibiotics may require surgical drainage and decortication. Surgical treatment for such patients should not be delayed.
Results.
A successful outcome is defined by drainage of the abscess without need for a more invasive procedure such as a video-assisted thorascopic surgery, surgical thoracostomy, or thoracotomy. Success rates for image-guided drainage of empyema or complicated parapneumonic effusions range from 70% to 94% in retrospective studies. With the use of intracavitary fibrinolytics in more complex cases with empyema or hemothorax, a success rate up to 92% has been reported. These success rates compare favorably with success rates of 35% to 75% for surgically placed chest tubes, although it is difficult to compare the radiologic and surgical series directly because the patient populations were so variable in these studies.
Most authors agree that early drainage is important. A high percentage of early-stage empyemas with free-flowing fluid can be treated with either surgically or percutaneously placed chest tubes. Failure of chest tube drainage is usually due to thick viscous fluid and loculations. Such collections resist even large-bore chest tubes, but it appears that greater success can be achieved with adjunctive use of intrapleural fibrinolytics. Once a pleural peel develops, decortication is usually required, although there are some authors who suggest that some pleural peels may resolve spontaneously after treatment of underlying empyema ( Fig. 68-5 ). In debilitated patients who develop pleural peels, conservative management can be tried, and in some of these patients decortication may be avoided. However, for otherwise healthy patients, the surgical literature suggests that decortication should not be delayed when there is persistent pleural sepsis in the presence of a pleural peel.
In the surgical literature, rib resection, limited thoracotomy, and thorascopic débridement have all been advocated as the treatment of choice for empyema. Currently there is a trend toward early decortication. Ashbaugh reviewed the effects of delayed surgical treatment and the choice of operation on the morbidity rate in patients with empyema. He concluded that decortication is the procedure of choice when tube drainage fails. Decortication had the lowest morbidity and mortality rates when compared to tube or open surgical drainage. The timing of decortication is important. The fibroblastic pleural peel usually organizes by 8 weeks, at which time a decortication can be performed. There is also an early window during the first 2 to 3 weeks before the fibroblastic reaction begins when decortication can be performed easily. However, between 3 and 6 weeks, the fibroblastic membrane is poorly developed and adherent to the lung. Attempts to perform decortication at this time can lead to tearing of lung tissue and development of a bronchopleural fistula.
Complications.
Serious complications from “blind” insertion of surgical chest tubes have been reported. These include lung laceration, diaphragmatic and intraabdominal organ injury, and neurovascular injury. None of these complications has occurred in the radiologic series. Complications associated with percutaneous drainage include pneumothorax, hemothorax, intercostal neurovascular bundle injury, perforation of major organs and arteries, subcutaneous emphysema, and pulmonary edema due to reexpansion of the underlying lungs. Other reported complications including bronchopleural fistula and transgression across the diaphragm or into the lung parenchyma have been described.
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