33rd Annual Scientific Meeting proceedings

Surgery to the extrahepatic biliary tree can vary from being almost a routine elective procedure to an extreme challenge, often with significant intraoperative decision-making required. Additionally, timing of surgery and the patient’s physiologic status will affect outcome. It is worth having excellent critical care and anesthesia support for these cases, as many will present to surgery late in the disease and in crisis, requiring significant instrumentation and cardiovascular support. When going into surgery on these cases, the surgeon should be prepared to perform a variety possible procedures, not just what was initially intended.

Variable anatomy
There is considerable interspecific variation in the extrahepatic biliary system in mammals, and some intraspecific variation. Not only are the hepatic ducts variable in number and location, the length and width of a normal cystic duct can vary, as well as the length of the intramural portion of the bile duct. The different ductal anatomy of the cat v. dog is well described, with the major duodenal papilla in the dog comprising largely of the bile duct, whereas a combined entry of pancreatic and bile ducts entering in the cat. These anatomic differences can play a role not just in surgery, but also in disease presentation, with pancreatitis often present, sometimes obstructive. Bilobed gallbladders occur in both species, more commonly in cats, as incidental findings without clinical concern. It is prudent to be familiar with the variations of a normal biliary system, because many disease situations will make anatomical recognitions much more difficult, with marked dilation, inflammation and thickening, and discoloration distorting the appearance.

Pathologies in which to consider cholecystectomy
The most important consideration before removing the gallbladder in any species is whether the remaining extrahepatic biliary tree is patent, or is the gallbladder needed for biliary diversion, such as a cholecystoenterostomy (CCD or CCJ). The bottom line is that bile has to flow from the liver to the intestines, one way or the other.

By far the most common indication for cholecystectomy in dogs is gallbladder mucoceles ± cholecystitis. With gallbladder mucoceles, it is usually clear that diversion (CCD or CCJ) would not be prudent due to the pathology of the gallbladder itself. However, although gallbladder mucocele is one of the most common situations in dogs in which cholecystectomy is routinely performed, there are several other conditions where it may be indicated but decision-making should be considered more carefully. In cats, decision-making can be even more complex due to more frequent concurrent pancreatic involvement, and intrahepatic inflammatory disease.

Conditions (other than mucoceles) where cholecystectomy is considered include gallbladder trauma, non-obstructive cholelithiasis, displacement and neoplasia. Traumatic gallbladder rupture itself is actually quite rare (in fact, most cases are probably iatrogenic), probably due to the sliding nature of the deeply fissured liver lobes in dogs and cats. It is more common to see either bile duct or cystic duct tears due to the traction applied to the biliary tree from rapid acceleration/deceleration forces associated with severe blunt trauma. In these situations, it may be imperative to retain the gallbladder for biliary diversion. Complicating factors with traumatic ruptures to the biliary tree include the presence of concurrent injuries compromising cardiovascular and/or respiratory function, and delayed recognition of bile leakage due to attention being directed towards life-threatening injuries. The location of the tear will determine the type of surgery, but it is critical to accurately determine severity, the location and number of disruptions to the tract (including parenchymal damage to the hepatic ducts as they exit the liver). The bile duct may be repaired over stents, especially in larger dogs, but if this is not feasible then ligation of the duct either side of the tear or and cholecystoduodenostomy should be performed. So be absolutely sure of the integrity of the biliary tree before removing the gallbladder. This advice also holds true for traumatic displacement of the gallbladder (and usually liver) into the pleural cavity with a diaphragmatic rupture (the gallbladder can also be compromised in peritoneopericardial diaphragmatic hernia). Once upon reducing herniated contents, assessment of viability can be performed and an intraoperative decision made as to what resections (eg, liver lobectomy, cholecystectomy) are necessary.

Cholelithiasis is not nearly as common in dogs and cats as it is in humans, likely due to different composition of bile between species, but nevertheless gallstones can occur in our small animal patients. With the advent of endoscopic retrograde cholangiopancreatography (ERCP) in human surgery, many choleliths can be removed via scope, but this is not yet widespread at all in veterinary medicine. Of course, a cholecystotomy can be performed to remove gallstones, but as long as the remaining biliary tree can be flushed without obstruction, the preferred intervention is cholecystectomy.

Neoplasia of the biliary tree (cholangioma, gallbladder carcinoma, bile duct carcinoma and biliary cystadenoma in cats) is not nearly as common as primary hepatic neoplasia in small animals, and when it does occur it is often within the parenchyma of the liver. Unfortunately, often by time of diagnosis gallbladder carcinoma is advanced with regional lymph node metastasis. Staging 3-phase CT is indicated and discussion with owners with respect to prognosis is warranted. If a gallbladder lesion is noted incidentally during abdominal surgery, cholecystectomy would be indicated over partial cholecystectomy or biopsy.

Summary

Know the anatomy.

Be prepared to change your surgical plan.

Be familiar with multiple techniques.

Biliary flow to the intestines is mandatory.