Surgery of the liver (Proceedings)

Liver lobar anatomy and biopsy

The liver, the largest gland in the body, is divided into six lobes (from a surgical perspective): left lateral, left medial, right lateral, right medial, quadrate, and caudate lobes. The caudate lobe has two processes - papillary and caudate. Biopsy of the liver is frequently performed during exploratory laparotomy. There are multiple methods of performing a surgical liver biopsy, including ligature fracture, instrument fracture, biopsy punch, and wedge resection techniques. All except the biopsy punch method sample tissue from the edge of a liver lobe. The ligature fracture technique utilizes a loop of suture material (e.g., 2-0 PDS) to isolate liver tissue at the edge of a liver lobe. Tightening the loop helps provide hemostasis. The tissue distal to the ligature is sharply excised. The instrument fracture technique may be employed on thicker or denser portions of liver. The proposed biopsy site is isolated by crushing the hepatic parenchyma using an instrument (e.g., Carmalt forceps) and placing overlapping full-thickness mattress sutures in the liver proximal to the clamp. Sharply excise tissue distal to the clamp. The biopsy punch method involves the use of a skin biopsy punch. Any portion of the liver may be sampled using this method; however smaller, partial thickness samples are obtained. Drill and twist the biopsy punch into the hepatic tissue to obtain the specimen. Avoid excessively deep penetration into the hepatic tissue so that larger vessels are not encountered. Achieve hemostasis by inserting either a topical hemostatic agent (e.g., Gelfoam) or an omental plug into the defect. Larger hepatic biopsy samples can be obtained using the wedge resection technique.

Biliary tract surgery

The reported incidence of biliary tract disease requiring surgery in dogs and cats is low. Biliary obstruction, leakage, and gallbladder disease are the most commonly reported conditions. Essentially all instances of biliary leakage should have surgery. Not all cases of biliary obstruction or gallbladder disease need surgery. Biliary obstruction due to pancreatitis usually resolves with medical management and time. Differentiating between surgical and nonsurgical causes of extrahepatic biliary tract disease can be challenging.

The extrahepatic biliary system is composed of hepatic ducts (from each hepatic lobe), a cystic duct (from the gallbladder to the first tributary from the liver), the bile duct, and the gallbladder. Bile drains from the hepatic ducts into the bile duct and is stored and concentrated in the gallbladder. The bile duct courses dorsal to the hepatogastric ligament and terminates in the duodenum approximately 6 cm aborad to the pylorus.

Surgical techniques applicable to the biliary system include cholecystotomy, cholecystectomy, repair of bile duct injury, and bile flow diversion (cholecystoenterostomy). Selection of the appropriate surgical procedure involves knowledge of the clinical course of the patient and accurate assessment of the biliary tract at surgery.

Exploratory laparotomy should enable accurate assessment of the biliary tract. Evaluation can be compromised by diminished visualization of the cranial abdomen because of inappropriate incision location (paracostal extension of a midline approach may be necessary), presence of effusion, adhesion formation (particularly involving the gallbladder), and space-occupying disease processes (e.g., neoplasia). Thorough evaluation of bile duct patency and integrity necessitates either a cholecystotomy, duodenal enterotomy over the major duodenal papilla or both. A catheter should be placed into the bile duct from either direction and flushed with saline to assure patency and integrity of the bile duct. While catheter placement is often challenging, retrograde placement from the duodenum is generally easier to accomplish than normograde placement. Determination of site of leakage or obstruction and relief of obstruction are potential goals of catheter placement.

Cholecystotomy

Cholecystotomy may be indicated to remove choleliths or inspissated bile, to biopsy or culture the gallbladder wall, and to provide access for catheterization of the bile duct. Pack off the gallbladder using moistened laparotomy sponges. Place stay sutures near the proposed incision in the fundus of the gallbladder. Evacuate the contents and submit a sample for culture and susceptibility testing. Catheterize the bile duct and flush with saline to verify patency. Close the incision with one or two layers using a simple continuous pattern of synthetic absorbable suture material (e.g., 4-0 polydioxanone suture). If verification of bile duct patency is not possible, perform a duodenal enterotomy to provide access to the major duodenal papilla for catheterization.

Cholecystectomy

Indications for cholecystectomy include cholelithiasis, necrotizing or recurrent cholecystitis, biliary mucocele, neoplasia, and possibly gallbladder trauma. The technique of cholecystectomy varies from routine to challenging depending, in part, on the degree of adhesions present near the gallbladder. With minimal or no adhesion formation, cholecystectomy is usually well tolerated by the patient. A more guarded prognosis is appropriate for the patient with biliary mucocele and extensive adhesions.

Elevate the gallbladder from the liver by sharp and blunt dissection. Achieve hemostasis using electrocautery and vascular ligation. Free the cystic duct to its junction with the bile duct. Verify patency of the bile duct by catheterizing it via cholecystotomy or the duodenal papilla. Doubly ligate the cystic duct and associated cystic artery while avoiding injury to the bile duct. Submit appropriate samples for microbiologic and histologic testing.

Repair of common bile duct injury

The surgical technique used for lacerations of the bile duct depend on its diameter (> 5 mm diameter is recommended), location of the defect, and extent of injury. Achieving a secure seal of a bile duct tear while maintaining patency is difficult to achieve, in part, because diversion of bile during the healing process seems especially challenging in small animals. Unless the bile duct diameter is enlarged due to previous disease, the small diameter of the bile duct in many dogs and all cats precludes successful suturing of a defect without either subsequent leakage or stricture formation. Factoring in the relatively inaccessible location of the bile duct and adhesion formation makes successful suturing even less likely. Place a catheter from the duodenal papilla into the bile duct beyond the defect. After careful debridement, suture the defect using simple interrupted sutures (e.g., 5-0 polydioxanone suture). The distal end of the catheter may be tacked to the duodenal mucosa with absorbable suture (e.g., 4-0 surgical gut). If the injury is not amenable to being sutured, ligate the bile duct above and below the traumatized region and provide bile flow diversion (cholecystoenterostomy).

Bile flow diversion (cholecystoenterostomy)

Diversion of bile flow is indicated if the bile duct is obstructed or if the duct has been severely traumatized. Bile flow diversion procedures require a gallbladder that is not involved in the primary disease process. Two different diversion procedures are possible in the dog or cat: cholecystoduodenostomy or cholecystojejunostomy. The first procedure is preferred, as there are more complications with cholecystojejunostomy. A stoma is created between the gallbladder and the intestine. The stoma should be of adequate size (> 2.5 cm) to minimize potential of ascending cholecystitis. Mobilize the gallbladder from the liver and position it adjacent to the antimesenteric surface of the descending duodenum. Assure that tension on the gallbladder and intestine is minimized. Pack off this area with laparotomy sponges and suture the intact gallbladder to the duodenum. Use a simple continuous suture pattern (approximately 4 cm long) placed between the serosa of the gallbladder and the serosa of the duodenum (original suture line). Drain the gallbladder and incise it parallel to the suture line for a distance of 3 cm. Make a similar parallel incision in the antimesenteric border of the duodenum while the duodenum is occluded proximal and distal to the incision site. Beginning with the edges closest to the original suture line, place a continuous suture line of absorbable suture material (e.g., 3-0 polydioxanone suture) from the gallbladder mucosa to the duodenal mucosa. Next suture the mucosal edges of the stoma farthest from the original suture line using the same material and pattern. Finally suture the serosal edges of the gallbladder and duodenum on the side farthest from the original suture line. Complications of cholecystoenterostomy include hemorrhage, anastomotic dehiscence, stricture of the anastomosis, and ascending cholangiohepatitis.

Obstructive or traumatic biliary tract disease may require surgery. Proper patient preparation should include correction of fluid and electrolyte imbalances, coagulation deficiencies, and infection. Early, effective surgical treatment of biliary tract obstruction or trauma, when appropriate, is indicated. Principles of biliary tract surgery, including accurate approximation of tissue layers, gentle tissue manipulation, maintenance of blood supply, maintenance of an adequate lumen, and avoidance of tension should be followed.

Hepatic trauma

Blunt or penetrating abdominal trauma does not usually lead to isolated liver injuries in dogs or cats. Partial or complete lobectomy is indicated when this is the simplest method of treating a traumatized liver lobe with persistent hemorrhage or severe parenchymal damage. Biliary tract rupture secondary to abdominal trauma may occur. Trauma to the biliary tract may necessitate bile flow diversion.