Percutaneous Biopsy and Abscess Drainage in the Abdomen and Pelvis

Indications

Indications for percutaneous biopsy are to (1) establish a benign diagnosis, (2) establish a malignant diagnosis, or (3) obtain material for culture or other laboratory analysis (e.g., molecular analysis, immunohistochemistry, experimental protocols). Departmental review of patient selection should be undertaken if less than 95% of image-guided percutaneous biopsies are being performed for these three indications. Additionally, it should be requisite that plans for treatment or further investigation be strongly influenced by the biopsy results.

Contraindications

There are few absolute contraindications to biopsy. A severe uncorrectable coagulopathy or a patient’s inability to cooperate, endangering the patient or the interventionalist, should prompt review of alternative forms of diagnosis. Acute intraprocedural change in clinical status should result in consideration of cessation of the procedure.

Relative contraindications before biopsy of a lesion are more numerous and complex with consideration of the location’s propensity to bleed, ease of identifying and controlling a complication (e.g., bleeding or pneumothorax), and patient comorbidities. The following represent common relative contraindications:

• • Correctable coagulopathy (prothrombin time > 15 seconds; international normalized ratio > 1.5; platelets < 50,000); patient not withdrawn from anticoagulation for a safe period, which varies depending on biopsy-site risk (e.g., low-molecular-weight-heparin [Lovenox], 24 hours for renal and 12 hours for all other sites; warfarin [Coumadin], 5 to 7 days for all biopsy sites; clopidogrel [Plavix], 5 days for all biopsy sites; acetylsalicylic acid [aspirin], 5 days for only renal biopsy; and new oral anticoagulants, 3 days for any nonsuperficial biopsy).

  • Unsafe target for biopsy (e.g., highly vascular tumor).

  • Absence of a safe pathway from the skin to the target site. Consideration should be given to use of other imaging modalities (e.g., ultrasound vs. computed tomography [CT] guidance) or other sites of access (e.g., percutaneous vs. transjugular hepatic biopsy).

  • Pregnancy.

Although gross ascites is frequently suggested as a contraindication, there is remarkably little evidence that ascites in the absence of coagulopathy increases the risk related to percutaneous biopsy of abdominal lesions.

Biopsy of pregnant patients requires significant review and patient counseling. Imaging facilities should have policies and procedures in place to attempt to identify pregnant patients. If the use of ionizing radiation to perform a biopsy is needed during pregnancy, the patient should be counseled regarding the risk of radiation exposure to the fetus. Fetal radiation exposure should be in accordance with the principle of “as low as reasonably achievable.”

Preprocedural Evaluation

Before image-guided biopsy, review of clinical history (e.g., medical and surgical history, medications, allergies) should be undertaken. Relevant laboratory parameters should be noted, which have been better defined by recent Society of Interventional Radiology and Cardiovascular and Interventional Radiological Society of Europe guidlines.

A review of dedicated imaging is critical to successful biopsy, including appropriate imaging modality selection as well as planned needle route. The choice of imaging modality varies according to a number of parameters. A primary consideration in the past has been availability; however, most institutions now have 24-hour access to ultrasound, fluoroscopy, and CT. Widespread access and use of magnetic resonance imaging for biopsy guidance remains limited, but improved scanner designs focused on increasing interventional capabilities have made magnetic resonance imaging-guided biopsy a reality in some practices. The use of positron emission tomography/CT in malignancy evaluation at large tertiary care centers has led to increased application of positron emission tomography/CT-guided biopsies. The consideration most likely to dictate choice of modality is operator preference, which may be a reflection of formal residency training, physician group practice, or comfort with various types of image guidance.

Most abdominal and pelvic biopsies are performed under ultrasound or CT guidance; there are relative advantages and disadvantages to each modality ( Table 87.1 ). Ultrasound guidance is the preferred modality for percutaneous biopsy at many institutions. Biopsy needles are sonographically visible when the scan plane is optimized. Nonvisualization of the needle tip is most commonly due to misalignment of the needle and the transducer plane. Techniques for enhancing visualization of the needle tip include jiggling the needle tip, performing the “pump” maneuver, or injecting a small amount of air or saline through the needle tip. Commercially available needle guides can be obtained to perform ultrasound-guided biopsy. However, care needs to be taken while using these adjuncts because they do not substitute for proper technique or experience. Mobile lesions and lesions that require multiple imaging angles may be better suited to ultrasound-guided biopsy ( Fig. 87.1 ).

CT guidance can be employed in patients who are poor candidates for ultrasound. Deeper lesions obscured by bowel gas or limited by body habitus may be better visualized under CT guidance. CT guidance can also aid in percutaneous transosseous soft tissue biopsies. Limited scans through the target area allow localization of the target lesion. Occasionally, intravenous contrast material may be required to differentiate the target lesion from surrounding structures.

Equipment and Technique

Biopsy needles can be divided into three main groups: small-gauge aspiration needles, small-gauge core biopsy needles, and large-gauge core biopsy needles. There are limitations to the aspiration technique. Aspiration needles might provide cytologic samples that are scant or difficult to interpret, but the biggest disadvantage of this technique is that the architecture of the sampled tissue is not preserved. This technique may also require multiple passes, and it is important that concomitant cytopathologic evaluation of the aspirates be undertaken at the time of sampling. Involvement by on-site pathologists optimizes specimen procurement, ensuring that appropriate samples are taken as required for ancillary investigations (e.g., microbiology or molecular studies). Small-gauge core biopsy needles are designed to provide small tissue specimen for histologic analysis. Large-gauge core biopsy samples may improve diagnostic yield, but have historically been associated with increased risk. Core biopsy samples are now commonly required for genetic testing and long-term storage of material.

Fine-needle aspirations are initially performed with a nonaspiration (nonsuction) technique because suction can result in a significant amount of blood in the specimen. This technique relies on rapid movement of the needle tip within the target lesion; approximately 0.5 to 1 cm excursions are performed until the first hint of blood is noted in the needle hub. An air-filled syringe preattached to the needle is used to express the tissue from the lumen of the needle onto a slide for immediate review by a cytopathologist. The nonaspiration technique may yield limited specimen in organs with firm (e.g., heavily fibrotic) tissue. Manual (suction) aspiration with a syringe may be undertaken in these scenarios.

Two primary core needle biopsy designs exist in which the length of intended tissue harvest, needle throw, may be adjusted in fixed fashions, typically 1 cm, 2 cm, or 3cm in length. The first involves a spring-loaded needle, which is advanced to the edge of the lesion with the needle throw not visualized until after it is fired (BioPince, Argon Medical Devices, Frisco, TX, or Monopty, C.R. Bard/Becton Dickenson, Inc., Tempe, AZ). The other commonly used design has a manually controlled needle deployment, which is advanced through the lesion, before firing the spring-loaded needle sheath, thereby obtaining the sample (Temno, Becton Dickenson, Franklin Lakes, NJ) ( Fig. 87.2 ). The latter design allows the path of the needle to be seen before obtaining the sample. Care should be taken to ascertain that the needle throws not extend outside the lesion to be sampled, or if it does, that it does not result in injury to critical structures. There may be selected instances where normal tissue is required as a diagnostic adjunct to the abnormal tissue that is being sampled.

In general, the shortest route from the skin to the lesion should be taken, so long as no vital structures or organs are interposed. In the case of peripheral hepatic lesions, however, a biopsy path that traverses normal liver between the liver capsule and target should be chosen. This can help minimize the risk of intraperitoneal bleeding (particularly for vascular lesions such as slow-flow intrahepatic venous malformations) and potentially decreases the likelihood of needle-tract seeding. Certain lesions may merit use of nonstandard technique as well. For instance, a transintestinal approach may be necessary for lesions within the mesentery ( Fig. 87.3 ). Transsplenic biopsy may be necessary for lesions in the upper part of the abdomen that are not approachable even with a craniocaudal trajectory. Retroperitoneal and pelvic biopsies may be more safely approached posteriorly.

Certain organs merit special considerations before biopsy: the adrenal gland and the pancreas.

Complications

Complications of percutaneous biopsy are of two types: generic and organ specific. Generic complications (e.g., bleeding and infection) are common to all types of biopsy. The risk of clinically significant bleeding is low. Although increasing core needle gauge has historically been associated with increased risk of bleeding, clinically significant bleeding (e.g., requiring blood transfusion or embolization) is likely similar among needle sizes. Organ-specific complications are those that are only or most commonly associated with biopsy of a specific organ.

Major complications are defined as (1) unplanned admission to the hospital for therapy, (2) unplanned increase in the level of care, (3) prolonged hospitalization, (4) permanent adverse sequelae, and (5) death. Minor complications are defined as (1) complications requiring nominal therapy or (2) complications requiring a short hospital stay for observation.