Daniel J. Brockman, BVSc, CVR, CSAO, DACVS, DECVS, FHEA, MRCVS
Bile canaliculi in the liver combine to form the hepatic ducts. The number of hepatic ducts varies from 3–5; they join the extrahepatic biliary system at the cystic duct. The gallbladder lies in the right medial and quadrate liver lobes in the gallbladder fossa. One duct, the cystic duct, leaves the gallbladder and receives the hepatic ducts. After the last hepatic duct has joined the cystic duct, the duct travelling towards the duodenum becomes the bile duct or common bile duct. The common bile duct enters the duodenum on the major duodenal papilla. The bile duct tunnels submucosally aboral to the serosal attachment of the duct; this is more pronounced in dogs than cats. The gallbladder wall contains smooth muscle and the bladder is lined with epithelium, which is rich in mucous-secreting goblet cells.
1. Radiography. Plain film radiography can demonstrate radiodense choleliths. In addition, focal or generalised peritonitis can be suspected when poor abdominal detail is present. Contrast radiography using cholecystopaques such as Cholografin is of limited value since the quality of the study is adversely affected by elevation of serum bilirubins. The placement of a catheter directly into the gallbladder at surgery will permit intraoperative cholecystography and demonstrate any ductal abnormalities. Many of the radiographic techniques have been superseded by sonographic examination of the abdomen.
2. Ultrasonography. Skilled ultrasonographic examination of the abdomen can yield valuable information about the size and contents of the gallbladder and the size and contents of the biliary tree. It is rarely possible to diagnose leakage of bile ultrasonographically, but it may help direct an abdominocentesis needle into a pocket of fluid to improve the diagnostic yield of this procedure. A recent study of the sonographic evaluation of the feline common bile duct suggested that, in that species, a common bile duct diameter of 0.5 cm or greater was highly indicative of biliary obstruction.
3. Hepatobiliary scintigraphy. Use of 99mTc-diisopropyl IDA has been described in dogs and cats. This technique has the advantage of being noninvasive and is still useful in the face of bilirubinaemia. The principle value of this technique, therefore, is in the diagnosis of extrahepatic biliary obstruction among patients wherein hepatic and extrahepatic causes of jaundice are possible.
4. Computed tomography. CT has shown itself to be very useful in human patients with focal abdominal inflammation and/or peritonitis (e.g., appendicitis) and is potentially useful for patients with disease of the biliary tree.
Conditions and Surgical Techniques
Extrahepatic Biliary Obstruction
Clinical features. The clinical features of biliary obstruction may be vague and nonspecific. They include: icterus, inappetence, vomiting, abdominal discomfort, diarrhoea, acholic feces. Laboratory data acquired should include complete blood count (CBC), biochemistry screen, urinalysis, coagulation panel, and PIVKA. Electrolyte and acid/base abnormalities should be addressed prior to surgery wherever possible. Vitamin K therapy should be given if indicated.
NB temporary tube cholecystostomy may be done, under short GA, to permit patient stabilization prior to definitive surgery.
1. Cholelithiasis. Clinical disease resulting from cholelithiasis is rare among dogs and cats. When they do cause disease, choleliths usually cause intermittent or constant biliary obstruction or are associated with cholecystitis (see later). Most often, choleliths are composed of calcium bilirubinate or are simply bilirubin concretions. Between 30–50% of choleliths are visible on plain film radiographs. Most choleliths can be visualized ultrasonographically. Obstruction occurs at the level of the common bile duct and may be right at the entry point of the CBD into the duodenum (at the sphincter). The surgical management of these patients is determined by one's ability to free the common bile duct of obstruction. If the common bile duct can be cleared (by catheterization of the major duodenal papilla), the gallbladder and cystic duct are removed along with the cholecystoliths. If they cannot be removed, a cholecystotomy should be performed, the gallbladder evacuated, and a cholecystoduodenostomy performed. If the calculus is lodged at the major duodenal papilla, a sphincteroplasty (sphincterotomy) can be performed. The sphincter is enlarged to permit removal of the stone and the sphincter mucosa is sutured to the duodenal mucosa, thereby permanently widening the sphincter opening. Most veterinary patients are too small for this procedure to be performed accurately. In all cases, cultures should be taken of bile, gallbladder mucosa, and cholelith. A gallbladder biopsy may also be prudent. The cholelith may be analyzed.
2. Chronic fibrosing pancreatitis. Can result in icterus secondary to compression of the CBD. Diagnosis of this condition is greatly enhanced by sonographic evaluation of the abdomen. The treatment options include biliary stenting and cholecystoduodenostomy. Biopsy of the pancreas will confirm the diagnosis and rule out neoplastic causes.
3. Neoplasia. The most common tumors that cause obstruction of the CBD are tumors of the exocrine pancreas, gastric tumors, and proximal duodenal neoplasia. Treatment is usually only of palliative value and typically either biliary stenting or cholecystoenterostomy. The primary tumor is either biopsied or excised.
4. Inflammatory polyps. These have been described in the common bile duct of cats. The possibility of benign disease should always make one cautious about condemning an animal on the basis of gross pathological appearance.
Traumatic Disruption of the Extrahepatic Biliary Tract
Rupture of the EBT can affect either the gallbladder or any part of the ductal system. In addition, avulsion of the common bile duct can occur. These injuries may result from blunt or penetrating abdominal trauma. The result of bile leakage is a sterile bile peritonitis unless a preexisting cholecystitis was present or if contamination of the abdominal cavity occurred as a result of the initial trauma. Patients may be presented anytime from 3 to 30 days after the traumatic incident.
Clinical features include: vomiting, abdominal distention, abdominal pain, inappetence, lethargy, pyrexia, and weight loss. Diagnosis of either focal or generalized peritonitis is made by standard techniques. The demonstration of bilirubin in the abdominal fluid that is 2x (or more) the serum bilirubin level is indicative of bile peritonitis.
Surgical management is by cholecystectomy if the gallbladder is ruptured and the common bile duct is patent. If a hepatic duct is ruptured, it can be ligated and collaterals from the associated liver lobe(s) will develop. If the CBD is torn or avulsed, the best surgical option is to ligate the CBD and perform a cholecystoduodenostomy. Choledochoduodenostomy (anastomosis of the CBD to the duodenum) may be attempted in large dogs, but it is usually not successful in small dogs and cats. Anastomosis of the CBD may be attempted, but stricture formation may be common following this procedure in veterinary patients.
Cholecystitis, Biliary Sludge, Biliary Mucocele, and Gallbladder Infarction
Cholecystitis in dogs has been classified according to the human disease, namely: Type I, which is cholecystitis with acute rupture of the gallbladder resulting in septic bile peritonitis; Type II, which is cholecystitis with chronic bile leakage and focal peri-hepatic/biliary abscess formation; and Type III, cholecystitis with chronic abscess and fistulation. Clinical signs are variable but similar to those previously mentioned for other diseases of the biliary tract. In addition, superimposition of signs of infective peritonitis occurs. The treatment for these conditions is cholecystectomy, debridement of diseased tissue, and therapy for the attendant peritonitis. Septic bile peritonitis carries a much poorer prognosis than sterile bile peritonitis.
Chronic biliary sludge formation and the presence of bile and mucous plugs in the gallbladder can also cause clinical disease. The disease usually relates to intermittent biliary obstruction and the presence of cholecystitis. Surgical management, again, is by cholecystectomy.
Long-Term Complications of Cholecystoenterostomy
These are largely unknown in veterinary patients. In humans, chronic cholangiohepatitis has led to the development of techniques that interpose an antiperistaltic loop of bowel between the gallbladder and the true enterostomy site in an attempt to reduce reflux of intestinal contents. The development of bacterial overgrowth in the antiperistaltic bowel loop may actually increase the incidence of cholangiohepatitis. In dogs and cats, it should be assumed that chronic cholangiohepatitis will occur and the animals will be monitored carefully and treated with antibiotics and anti-inflammatory drugs, as needed.
Stricture/stenosis of the opening between the GB and intestine has been observed by several workers and has led to the recommendation to make the stoma at least 4 cm long.
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