16 Ameet Singh In veterinary medicine, liver biopsy is a commonly performed procedure because many diseases of the hepatobiliary system do not require surgical intervention. Biopsy can provide a definitive diagnosis, which can guide additional diagnostic or therapeutic measures. In addition, liver biopsy can provide important prognostic information for the clinician and pet owner. Indications for liver biopsy are numerous and may include elevated hepatic enzyme activities for more than 30 days, investigation of ultrasonographically identified lesions, abnormal liver size, and staging for neoplastic disease.1-4 Several techniques for liver biopsy have been described in the veterinary literature such as percutaneous cutting needle biopsy, with or without ultrasound guidance,5 laparoscopic biopsy,1,2,6-9 or biopsies harvested at the time of celiotomy.1,3 Each technique for liver biopsy carries its own potential for complications and limitations, with bleeding the most commonly described. Bleeding can be further exacerbated in patients with hepatobiliary disease10; therefore, the technique of liver biopsy must be selected carefully, taking into account the potential risks for the individual patient. Laparoscopy is a minimally invasive technique for procedures of the abdomen and provides numerous advantages over open celiotomy, including improved illumination and detail of abdominal organs, reduced postoperative pain, and rapid return to function for patients.11-13 Diagnostic laparoscopy is commonly performed in human and veterinary medicine and can be used to obtain high-quality tissue biopsies, assess the resectability of lesions, and stage neoplasia.6,7,14,15 Percutaneous cutting needle biopsy, with or without ultrasound guidance, is also a minimally invasive technique for liver biopsy.5 However, this technique has been associated with reduced diagnostic efficacy compared with wedge biopsy of the liver obtained at the time of celiotomy or postmortem.16 In one study, morphologic diagnosis obtained via cutting needle biopsy agreed with the definitive diagnosis obtained via wedge biopsy in only 48% of cases.16 The discordance between biopsy techniques was attributed to the median surface area of the cutting needle liver biopsy, which was one quarter the size obtained via wedge biopsy, resulting in reduced numbers of portal triads and hepatic acini in the cutting needle biopsy specimen.16 The minimum number of portal triads required in a biopsy specimen to obtain an accurate morphologic diagnosis in veterinary medicine has not been established; however, a previous report suggested that more than six to eight were adequate in human patients.17 Feline patients undergoing cutting needle biopsy are at risk for vagotonic shock after rapid fire of the biopsy needle, and some authors have suggested avoiding this method in this species.3 The use of laparoscopy for liver biopsy maintains the minimally invasive advantage of the cutting needle technique but is able to obtain diagnostic biopsy samples similar to what can be obtained at the time of celiotomy.2,6,8,9 Furthermore, the liver biopsy sites can be selected under direct laparoscopic visualization of liver lobes, and hemorrhage can be monitored and addressed if required by the surgeon. In a canine experimental study comparing various techniques for liver biopsy, laparoscopic liver biopsy (LLB) of the left lateral lobe produced biopsy specimens that were adequate for histologic investigation with 16.8 ± 1.43 and 18.1 ± 2.51 portal triads from peripheral and central locations, respectively.2 An additional finding in this study was that regardless of technique for liver biopsy, hemorrhage was minimal (<2 mL), and normal coagulation occurred rapidly.2 These results must be interpreted with caution because these were healthy experimental dogs without evidence of hepatobiliary disease. A retrospective study of dogs undergoing LLB found that this method was associated with minimal morbidity and mortality and produced adequate samples for histologic interpretation.8 The authors suggested submission of multiple LLB specimens for histologic interpretation because disagreement in diagnosis was found in 14% of cases.8 The results from another recent study evaluating dogs undergoing LLB as the sole diagnostic procedure performed corroborated safety results with the findings by Petre.9 Cholecystocentesis is a diagnostic procedure most commonly performed during investigation of hepatobiliary diseases of bacterial origin.3,18,19 In cats, cholangitis or cholangiohepatitis is one of the most commonly diagnosed hepatobiliary diseases with ascending bacterial infection most commonly implicated as the inciting cause.20,21 Treatment is based on appropriate bacterial culture and susceptibility testing, and percutaneous, ultrasound-guided cholecystocentesis has been shown to be a safe, minimally invasive, and effective procedure in dogs22,23 and cats.18 Laparoscopic cholecystocentesis (LC) provides an additional minimally invasive technique for bile sampling and can be performed concurrently at the time of LLB or other laparoscopic procedures. Advantages of LC include the use of laparoscopic guidance for needle placement into the gallbladder and having the ability to monitor for bile leak or hemorrhage into the peritoneal cavity. Diagnostic laparoscopy can also allow for investigation of the extrahepatic biliary tract and any other abnormalities in the abdomen. Studies comparing the safety and efficacy of percutaneous, ultrasound-guided cholecystocentesis with LC are lacking in the veterinary literature. Extrahepatic biliary obstruction (EHBO) can result in devastating metabolic abnormalities, such as coagulopathy, reduced Kupffer cell function, increased circulating endotoxins, and intra- and postoperative hypotension in dogs and cats.24-29 Surgery for EHBO is associated with prolonged operative times and high mortality rates,24,25,27 and preoperative biliary drainage has been considered as a therapeutic option to improve postoperative outcomes.29,30 A clinical study in three dogs reported the successful treatment of EHBO secondary to pancreatitis with percutaneous ultrasound-guided cholecystocentesis.23 In humans, controversy exists as to the benefit of preoperative biliary drainage via cholecystocentesis (laparoscopic or ultrasound guided) because bile has many important functions in the gastrointestinal tract.31-33 In veterinary medicine, most often a one-stage, definitive surgical procedure (biliary rerouting or cholecystostomy tube placement) is performed in cases with EHBO. However, the development of endoscopic retrograde cholangiography or laparoscopic evaluation of the extrahepatic biliary tract may result in a larger number of cases in which LC may represent the ideal treatment option for the treatment of EHBO. The parenchyma of the liver is divided into six lobes (from left to right): left lateral, left medial, quadrate, right medial, right lateral, and caudate. The caudate lobe is further subdivided into the caudate and papillary processes. Deep fissuring separates each lobe and allows the lobes to stack upon each other during movement, preventing tearing of the parenchyma. The liver is fixed at its cranial aspect by the coronary and left and right triangular ligaments and to the ventral portion of the abdominal wall and sternal portion of the diaphragm by the falciform ligament. Minor support is provided by the hepatorenal ligament, which attaches the right kidney to the renal fossa of the caudate lobe. The caudal aspect of the liver lobes, opposite to the hilar aspect, is relatively movable and provides a suitable target for LLB when diffuse hepatopathies are present. The hepatogastric ligament contains the bile duct, portal vein, and hepatic artery but does not provide additional support to the liver. The gallbladder (Figure 16.1) is a pear-shaped structure that resides in a fossa between the quadrate and right medial liver lobes. The cystic duct connects the gallbladder to the common bile duct, where a variable number of hepatic ducts also insert. The common bile duct then traverses within the hepatoduodenal ligament and inserts into the major duodenal papilla in dogs and cats. It is important to note the unique anatomy of the feline extrahepatic biliary tract in which the major pancreatic duct joins the common bile duct before its opening to the duodenum in the majority of cats.24,34 This intimate association makes cats more susceptible to EHBO with pancreatitis; in dogs, the minor pancreatic duct, which inserts into the duodenum at the minor duodenal papilla, distal to the insertion of the common bile duct, is the predominant duct.35 The liver has a unique dual blood supply in which 80% percent of its blood volume and 50% of its oxygen supply is provided by the portal vein and 20% of its blood volume and the remaining half of oxygen is provided by the hepatic artery which is a branch of the celiac artery. The cystic artery provides blood supply to the gallbladder, which is a branch of the hepatic artery.35 Figure 16.1 Laparoscopic view of the gallbladder, left of the adjacent quadrate liver lobe (patient positioned in dorsal recumbency). In many patients undergoing LLB or LC, a thorough diagnostic evaluation has already been performed and has led the clinician to search for a histopathologic diagnosis from a liver biopsy sample. This evaluation frequently includes serum biochemistry, complete blood count, urinalysis, and diagnostic imaging of the abdomen. Elevated hepatobiliary enzymes are commonly present in patients undergoing LLB. Abdominal radiography can provide information on liver size and whether loss of serosal detail is present that is consistent with free peritoneal fluid. In addition, radiography may identify choleliths that could be causing EHBO depending on their location within the biliary tract. Abdominal ultrasonography is critical in evaluating the liver parenchyma and size as well as gallbladder and common bile duct wall thickness, appearance of contents, size, and distension. In general, the decision to perform liver biopsy or cholecystocentesis is made after information gained from these diagnostic tests. Because the potential for hemorrhage from liver biopsy or cholecystocentesis site(s) is higher in patients with hepatic dysfunction,10 all patients should have coagulation testing (prothrombin time and partial thromboplastin time with or without buccal mucosal bleeding time) before LLB. Depending on the suspected underlying cause, three-view thoracic radiographs can be considered to rule out metastatic disease. Many patients requiring liver biopsy or cholecystocentesis are debilitated and metabolically compromised as a result of hepatobiliary dysfunction, resulting in coagulopathies and even development of ascites. Laparoscopy represents the ideal technique for liver biopsy in these patients because it is a minimally invasive and relatively quick procedure that reduces hemorrhage potential compared with open celiotomy. In addition, coagulation can be confirmed at biopsy sites, and this method provides samples from multiple lobes of suitable quality for histopathologic evaluation.2,6,8,9 Contraindications for LLB and LC are few. Liver biopsy is contraindicated in patients with thrombocytopenia (<80,000 platelets/mL) or marked prolongation of coagulation times because the risk for hemorrhage after biopsy is increased.5 However, in most patients undergoing LLB, clinical bleeding is rarely seen even in the face of abnormalities in coagulation testing.8,9 It has previously been shown that hemorrhage from liver biopsy is not correlated with coagulation times.3 If concerns are present, LLB can be performed with a technique thought to result in minimal hemorrhage (bipolar or ultrasonic vessel-sealing device, or pretied or extracorporeally tied loop ligature).6,36 Ascites can form in patients with severe hepatic dysfunction and portal hypertension and does not constitute an absolute contraindication for LLB. In the author’s opinion, laparoscopy represents the ideal method for liver biopsy in patients with ascites because these patients are often debilitated and coagulopathic; a method of rapidly obtaining a liver biopsy of diagnostic quality is needed. Removal of ascitic fluid at the time of LLB is not recommended or required. Albumin diffuses into the peritoneal space in patients with ascites, and abrupt removal of this fluid will result in exacerbation of hypoalbuminemia and rapid reaccumulation of ascites.3 Many of the contraindications for LLB are also present for LC. In addition, LC will be unsuccessful in improving bile flow in cases of gallbladder mucocele because the thick, sludge consistency of bile will prevent it from being aspirated through a small-gauge needle. Caution should be exercised when considering LC for EHBO. In cases of confirmed gallbladder mucocele, the surgeon should consider definitive therapy (laparoscopic or open cholecystectomy).
Liver Biopsy and Cholecystocentesis
Preoperative Considerations
Surgical Anatomy
Preoperative Diagnostic Evaluation
Patient Selection
Patient Preparation
Preparation for Surgery
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