Liver

Many patients with liver disease are anorectic and may require nutritional supplementation prior to surgery. Hypoglycemia occurs with severe hepatic insufficiency; monitoring blood glucose levels and supplementing fluids with glucose may be needed. Patients with massive ascites may have ventilatory disturbances due to diaphragmatic displacement and restriction of lung expansion. Removal of some abdominal fluid in such patients prior to anesthetic induction may help prevent hypoventilation. Patients with hepatic encephalopathy should be treated with dietary therapy, appropriate antibiotics, enemas, fluids, and other medications decrease or eliminate clinical signs prior to surgery.

Anesthetic Considerations

Animals with hepatic dysfunction may have impaired ability to metabolize and inactivate some drugs due to a decreased hepatic metabolic rate, decreased hepatic blood flow, decreased volume of distribution (i.e., of drugs that are highly protein bound), and a decreased extraction efficiency. Inhalation anesthetics are the preferred method of maintaining anesthesia in these patients. Heart rate and rhythm, respiratory rate, and urine output should be monitored. Hyperventilation may cause a significant decrease in portal blood flow. Halothane and isoflurane both cause decreases in portal blood flow but hepatic arterial blood flow tends to increase during isoflurane anesthesia, preserving hepatic oxygenation. Isoflurane, unlike halothane, has not been associated with postoperative hepatic dysfunction. Isoflurane is the inhalation agent of choice for patients with severe hepatic disease. Monitoring blood gases, blood pressures, blood glucose concentrations, hematocrit, and total protein is advantageous in these patients.

Surgical Liver Biopsy

Biopsies of the liver should be routinely obtained during exploratory laparotomy in animals with known or suspected liver disease. Surgical biopsy allows the entire liver to be thoroughly inspected and palpated, and focal lesions to be biopsied for histopathology, culture, and/or copper analysis. Furthermore, hemorrhage from the biopsy site can be readily identified and controlled with proper technique. If generalized hepatic disease is present, the biopsy can be taken from the most accessible site (marginal biopsy samples). With focal disease, the entire liver should be carefully palpated for the presence of intraparenchymal nodules or cavities and representative samples obtained. The information gained from histologic examination of the liver may prove beneficial in determining prognosis, diagnosis, and long-term management of patients with hepatic dysfunction.

A biopsy of the hepatic margin may be obtained by the "guillotine" method. Place a loop of suture around the protruding margin of a liver lobe. Pull the ligature tight and allow it to crush through the hepatic parenchyma before tying it. As the suture tears through the soft hepatic tissue, vessels and biliary ducts are ligated. Hold the liver gently between the fingers and using a sharp blade, cut the hepatic tissue approximately 5 mm distal to the ligature (allowing the stump of crushed tissue to remain with the ligature). Do not handle the biopsy sample with tissue forceps to avoid crushing it and causing artifacts. Place a portion of the sample in formalin for histologic examination; reserve the remainder for culture and cytologic examination. Check the biopsy site for hemorrhage. If hemorrhage continues, place a pledget of absorbable gelatin foam over the site. Alternately, if a focal (non-marginal) area of the liver is to be biopsied, use a punch biopsy or Tru-cut biopsy or place several overlapping guillotine sutures around the margin of the lesion and excise it. With a punch biopsy use caution to avoid penetrating more than half the thickness of the liver with each biopsy. Apply pressure to the site until bleeding stops. If hemorrhage continues, place a pledget of absorbable gelatin foam over the site.

Biliary System

Diseases of the biliary system are relatively uncommon in dogs and cats, as compared to human beings, because of the low incidence of cholelithiasis in the former species. The most common cause of bile leakage in dogs and cats is blunt or penetrating trauma of the gall bladder or biliary ducts. Occasionally, biliary obstruction may be noted following trauma, calculi, or neoplasia. This lecture will discuss definitive treatment of extrahepatic biliary disease in small animals.

Clinical Signs

The clinical signs associated with leakage of the biliary system are often insidious in onset. Many times there is a delay of several weeks following trauma before the onset of clinical signs referable to the biliary system are noted. Early signs of biliary leakage are vomiting, anorexia, lethargy, and abdominal pain. Signs of abdominal discomfort and systemic disease often are not present until the bile becomes infected. Because bile salts are toxic to tissues and cause tissue necrosis, peritonitis usually occurs secondarily in chronic, untreated bile leakage. Animals with bile leakage generally die due to the effects of bacterial peritonitis. Clinical signs associated with obstructive diseases depend on the cause of the obstruction. Icterus, abdominal pain, vomiting, depression, fever, weight loss, and anorexia may be noted.

Diagnosis

A history of trauma is frequently present in patients with biliary tract leakage. Abdominal radiographs may show evidence of fluid accumulation and loss of detail. Serum biochemical abnormalities include increased total bilirubin and serum alkaline phosphatase. Bilirubinuria may be present and occasionally the animals have clay-colored stools. Abdominocentesis should be performed on all animals in which bile peritonitis is suspected. The total bilirubin should be higher in the fluid than in serum in animals with bile leakage.

Animals with obstructive disease are generally icteric. Total bilirubin is elevated and serum alkaline phosphatase is usually markedly increased. Survey abdominal radiographs may demonstrate radiopaque stones. Ultrasonography may also indicate dilated biliary ducts. Intravenous cholangiography or nuclear scintigraphic procedures outlining the biliary system may aid in the diagnosis of obstructive biliary disease.

Preoperative Considerations

Many patients with liver disease are anorectic and require nutritional supplementation prior to surgery. These animals may also have to tendency to bleed extensively follow minor surgical manipulations due to concurrent clotting abnormalities. Last, but not least, these animals are often hypoalbuminemic. Albumin levels less than 2.0 gm/dl may interfere with normal wound healing.

When anesthetizing animals with liver disease it should be remembered that drugs that are metabolized by the liver, such as acepromazine and the barbiturates, may have a prolonged effect and should be used with caution. Normal bile is sterile, however in cases of cholangitis and cholecystitis the bile frequently contains bacteria. Antibiotic therapy should be based on culture and sensitivity. Administration of presurgical and postsurgical antibiotics is indicated. Empirically, ampicillin, cephalosporins, and chloramphenicol are often used because they are excreted into the bile.

Surgery of the Biliary Tract

Exploratory laparotomy should be performed in animals in whom leakage of bile into the abdomen is suspected, in animals with obstruction of bile flow that is not clearly due to pancreatitis, and in animals with suspected neoplasia (biliary tract, intestinal, or pancreatic), parasitic disease, or stones. During exploration, patency of the common bile duct needs to be assured by manually expressing the gallbladder, or by retrograde (i.e., from the duodenum) or occasionally normograde (i.e., from the gallbladder) catheterization of the duct.

Cholecystotomy

Cholecystotomy is rarely performed but may be indicated to remove some choleliths or when the gallbladder contents are inspissated and cannot be aspirated into a syringe. Pack the area surrounding the gallbladder with sterile, moistened laparotomy sponges. Place stay sutures in the gallbladder to facilitate manipulation and decrease spillage. Make an incision in the fundus of the gallbladder. Remove the gallbladder contents and submit for culture. Lavage the gallbladder with warmed, sterile saline. Catheterize the common bile duct via the cystic duct with a 3.5 or 5 French soft catheter and flush it to ensure patency. Close the incision with a one or two-layer inverting suture pattern using absorbable suture material (3-0 to 5-0).

Cholecystectomy

Diseases such as cholecystitis and cholelithiasis are best treated by cholecystectomy. Cholecystectomy may also be indicated for primary neoplasia or traumatic rupture of the gallbladder. Expose the gallbladder and incise the visceral peritoneum along the junction of the gallbladder and liver with Metzenbaum scissors. Apply gentle traction to the gallbladder and using blunt dissection free it from the liver. Free the cystic duct to its junction with the common bile duct. Be sure to identify the common bile duct and avoid damaging it during the procedure. If necessary, identify the common bile duct by placing a 3.5 or 5 French soft catheter into the duct via the duodenal papilla. Make a small enterotomy in the proximal duodenum, locate the duodenal papilla, and place a small red rubber tube into the common bile duct. Flush the duct to ensure its patency. Clamp and double ligate the cystic duct and cystic artery with non-absorbable suture material (2-0 to 4-0). Sever the duct distal to the ligatures and remove the gallbladder. Submit a portion of the wall plus bile for culture if infection is suspected. Submit the remainder of the gallbladder for histologic analysis if indicated (for cholecystitis or neoplasia). Close the duodenal incision with simple interrupted sutures of absorbable suture material.

From: Fossum TW, Small Animal Surgery. Mosby Publishing Co, St. Louis 2007.

Bile Flow Diversion

Bile flow diversion is indicated when common bile duct obstruction is present or the duct is severely traumatized and the gallbladder is not directly involved in the disease process. Cholecystojejunostomy or cholecystoduodenostomy is preferred over choledochoduodenostomy in dogs and cats because the latter procedure is often difficult to perform successfully due to the small size of the common bile duct in these species. If cholecystojejunostomy is performed, the proximal jejunum should be used to decrease the incidence of postoperative maldigestion of lipids. Additionally, duodenal ulceration may occur more commonly as a sequelae to cholecystojejunostomy than cholecystoduodenostomy. In dogs, it has been recommended that the stoma between the bowel and the gallbladder be at least 2.5 cm long to minimize the potential for obstruction of bile flow or retention of bowel contents in the gallbladder. Making the stoma too small is more apt to result in ascending or chronic cholecystitis than making it too large.

Mobilize the gallbladder from the liver as described for cholecystectomy. Place stay sutures approximately 3 cm apart in the gallbladder. Bring the gallbladder into apposition with the antimesenteric surface of the descending duodenum so that there is little or no tension on the gallbladder or intestine. Pack the area surrounding the gallbladder and duodenum with sterile, moistened laparotomy sponges. Place a continuous suture of absorbable suture material between the serosa of the gallbladder and the serosa of the duodenum near the mesentery (referred to as original suture line. Make the suture line 3 to 4 cm in length. Leave the ends of the suture long and use them to manipulate the intestine and gallbladder. Drain the gallbladder and make a 2.5 to 3 cm incision into it, parallel with the preplaced suture line. Have an assistant occlude the duodenum proximal and distal to the proposed incision site and make a similar parallel incision in the antimesenteric surface of the duodenum. Place a continuous suture line of absorbable suture material (2-0 to 4-0) from the mucosa of the gallbladder to the mucosa of the duodenum beginning with the edges closest to the original suture line first. Then, use the same suture material to suture the mucosal edges of the stoma farthest from the original suture line. Complete the stoma by suturing the serosal edges of the gallbladder and intestine over the near side of the stoma (i.e., the side furthest from the original suture line).