Diagnostic angiography in hepatobiliary and pancreatic disease: Indications

Angiography technique

In recent years, technologic advances have resulted in significant improvements in angiographic imaging. Cut-film angiography has been replaced with digital flat-panel detectors and biplane angiography units. Biplane angiography is capable of producing high-quality images in 3D views. These advances in technology allow for less contrast while minimizing radiation exposure to both patients and interventionalists.

Depending on the procedure, catheter angiography may be performed under conscious sedation or general anesthesia. Most angiographic procedures are performed on an outpatient basis; however, some patients may require overnight stay primarily for pain control after embolization-based interventions or for symptoms related to recovery from anesthesia. All patients are seen in the clinic before the diagnostic or interventional catheter angiography procedure. During this visit, indications for performing the procedure are reviewed. Additionally, patients are assessed for any history of cardiopulmonary or renal disease. Prior history of angiography or other surgical interventions are also assessed. A thorough physical examination, which includes a detailed pulse examination and an assessment of the airway, lungs, and heart, is performed. Finally, patients’ performance status is evaluated. Most institutions either use Eastern Cooperation Oncology Group (ECOG) performance status or Karnofsky performance status. The procedure is explained to the patient in detail and after a discussion of the risks and benefits of the procedure, written informed consent is obtained.

Relevant laboratory parameters reviewed before catheter angiography include serum creatinine and estimated glomerular filtration rate, hemoglobin and hematocrit levels, platelet count, and prothrombin time and international normalized ratio (INR). For liver-directed interventions such as embolization, serum bilirubin is also assessed. Additionally, a baseline 12-lead electrocardiogram (ECG) may be considered in patients with known or suspected cardiac disease. In patients with significant comorbidities, cardiology or geriatric consultation should be considered before the procedure to ensure the safety of conscious sedation or general anesthesia.

In patients with a history of preexisting renal impairment, prophylactic measures may be considered to lower the risk of further reductions in glomerular filtration rate related to the injection of iodinated contrast media during catheter angiography. Although multiple agents, including sodium bicarbonate and N-acetyl cysteine infusion, have been evaluated in randomized clinical trials (RCTs), intravenous (IV) hydration with normal saline (NS) solution before and/or subsequent to catheter angiography is the only measure currently recommended for this purpose.

The risk of bleeding from the puncture site is low, and hematomas complicate 1% of femoral punctures and 3% of nonradial upper extremity punctures. An abnormal bleeding profile related to thrombocytopenia or an elevated INR increases the risk of hemorrhage, but there is only weak association between magnitude of INR elevation and procedure-related hemorrhage. The need to correct an underlying coagulopathy is dependent on the specific procedure to be performed and the preference of the angiographer. Based on the current recommendations from the Society of Interventional Radiology (SIR) consensus guideline, diagnostic catheter angiography (arterial intervention with access size up to 6 French [F]) is classified as a procedure with a low risk of bleeding. For this procedure, SIR recommends platelet count above 20,000 × 10 ⁶ per liter and an INR of less than or equal to 1.8 for femoral access and 2.2 for radial access. Patients are advised to stop eating 6 hours before the procedure. IV hydration is recommended before, during, and after the arteriogram to diminish adverse effects of contrast media on renal function. The patient should also be encouraged to take ample fluids by mouth after the procedure.

The right common femoral artery is the most common access site. The left common femoral artery, axillary artery, brachial artery, or radial artery may be used as alternatives when clinically appropriate. In the past few years, there has been growing interest and expertise with radial artery access, particularly with interventional cardiology procedures. With appropriate technique, including ultrasonographic guidance at the time of arterial puncture, the trans-radial approach is associated with low risk of bleeding or vessel injury and affords patients the advantage of immediate ambulation after catheter angiography. Additionally, recent studies have demonstrated comparable procedural and clinical outcomes with the trans-radial approach when compared with the trans-femoral approach.

For all arterial access procedures, the desired puncture area is cleansed, and the patient is draped in a sterile fashion. In most centers, arterial entry is performed under real-time ultrasound guidance using a 21-gauge micropuncture set. The use of ultrasonography allows for assessment of the quality of the common femoral artery, depicts the position of the profunda femoris, and detects the presence of aberrant veins extending ventral to the puncture site. After entry into the vessel, the appropriate catheter is inserted for catheterization of the target vessel. After diagnostically adequate images are obtained, the catheter is removed, and one of a variety of closure devices is deployed to seal the arteriotomy; manual pressure may also be applied for 15 to 20 minutes, or until hemostasis is achieved. Patients are observed in a postprocedural area until they have recovered from sedation, and most can be discharged home 2 to 4 hours later.

Arterial anatomy

Arterial anatomy has been discussed elsewhere (see Chapter 2 ) and will only be briefly reviewed here. The most frequently encountered anatomy ( Fig. 21.1 ) is the left gastric artery, splenic artery, and common hepatic artery (CHA) taking origin from the celiac axis. The CHA divides into the gastroduodenal artery (GDA) and proper hepatic artery, with the latter dividing into the right and left hepatic arteries (RHA and LHA, respectively). The right gastric artery most often originates from the base of the left hepatic artery, and the cystic artery most often originates from the right hepatic artery, but considerable variations in the origins of these arteries exist. Moreover, accessory duodenal arteries, either representing a supraduodenal or a retroduodenal artery, are frequently encountered; this is critical to recognize when planning embolization, chemoembolization, and radioembolization.

The normal arterial supply to the liver is shown in Fig. 21.2 , which shows the commonly recognized variations of the LHA, taking origin from the left gastric artery, and the RHA taking origin from the superior mesenteric artery (SMA). It is important to recognize that either a part or the entirety of the RHAs and LHAs may have these variant origins. When the entire vessel has a variant origin, it is termed replaced. If the entire trunk does not take a variant origin, the vessel is termed accessory. For example, if the right lobe is supplied by an RHA originating from the CHA, as well as an RHA taking origin from the SMA, the latter would be termed an accessory RHA. If the entire right lobe was supplied by an artery taking origin from the SMA, it would be called a replaced RHA (see Chapter 2 ).

In most patients, the arteries to Couinaud segments I, II, III, and IV are branches of the LHA, and arteries to segments V, VI, VII, and VIII are branches of the RHA. The most variable segmental branch is to segment IV. Although most frequently arising as a branch vessel from the LHA, the segment IV artery may also take origin from the RHA, assuming the misnomer of a “middle hepatic artery” in older works. Separate origins of segment IVa, usually from the LHA, and segment IVb from the RHA are frequently identified. Also, a branch from the segment IV artery is often seen extending outside of the liver toward the abdominal wall along the midline, supplying the falciform ligament ( Fig. 21.3 ). Recognition of this vessel is important when conducting embolization, chemoembolization, or radioembolization to avoid nontarget embolization, which may result in ischemia or radiation dermatitis to the periumbilical region.

The RHA conventionally divides into an anterior (ventral) and a posterior (dorsal) branch. The anterior branch usually is more vertically oriented and supplies segments V and VIII. The posterior branch is usually more horizontally oriented and supplies segments VI and VII. More than one projection is usually required to ascertain with certainty which is the anterior branch and which the posterior branch. In the right anterior oblique projection, the anterior branch moves medially, and the posterior branch moves laterally when compared with the posteroanterior (PA) projection. The entire segmental arterial supply to the liver should be accounted for before hepatic arterial therapy, major hepatic resection, partial hepatectomy (see Chapters 101 and 118 ), or living donor liver transplantation (LDLT, see Chapters 109 and 125 ). Adjunctive techniques such as CBCT may be used, as necessary, to achieve optimal delineation of hepatic vascular anatomy.

The arterial supply to the pancreas is somewhat variable. The most consistent supply is to the pancreatic head, formed by a rich anastomotic arcade between the superior pancreaticoduodenal (SPD) artery arising from the GDA and the inferior pancreaticoduodenal (IPD) artery arising from the SMA ( Fig. 21.4 ). There, variable arteries give rise to both anterior and posterior divisional branches. Additional pancreatic arterial supply includes the transverse pancreatic artery, which runs along the middle portion of the long axis of the pancreas and may take origin from the arterial arcade in the head of the pancreas, directly from the GDA, or as a branch of the dorsal pancreatic artery, which variably originates from the CHA or the splenic artery ( Fig. 21.5 ). The transverse pancreatic artery may anastomose distal with the pancreatica magna artery, which typically arises from the splenic artery. A number of small branches from the splenic artery supply the pancreatic body and tail, but the number and location of these arteries vary and must be identified in each individual patient when clinically relevant (see Chapter 2 ).

Venous anatomy

The splenic vein and superior mesenteric vein (SMV) join to form the main portal vein (see Chapter 2 ). The inferior mesenteric vein (IMV) usually enters the splenic adjacent to the confluence, but it may also enter the SMV either at or just caudal to the confluence. The coronary vein most often drains into the cephalic aspect of the main portal vein just beyond the confluence of the SMV and splenic vein. The number and location of veins draining the pancreas is variable. Multiple small, unnamed veins drain directly into the splenic vein. Typically, the anterior SPD vein drains directly into the portal vein, and the posterior SPD vein drains into the SMV. The IPD veins drain into the SMV at the caudal margin of the pancreas, and the portal vein courses obliquely cephalad from near the midline toward the liver, where it divides to supply the right and left lobes. This division, as well as the division into segmental branches, is variable and must be delineated when clinically relevant for each individual patient.

Treatment of bleeding/hemorrhage

Bleeding from the liver, spleen, or pancreas is most often secondary to iatrogenic or noniatrogenic trauma, but it may occur spontaneously in patients with mycotic aneurysms, pancreatitis, or collagen vascular diseases. Angiography is usually not used to ascertain whether arterial hemorrhage is present but rather to precisely localize and treat the offending vessel. Embolization of arterial bleeding will be discussed elsewhere in this book (see Chapters 28 , 115 , and 116 ), but salient features will be reviewed in this chapter.