Comparison of covered versus uncovered wire mesh stents in the canine biliary tract.

Self-expanding wire mesh stents have been developed for endoscopic placement across malignant biliary strictures, but tumor ingrowth may limit the usefulness of open mesh stents. We reasoned that coating the wire mesh might prevent tumor ingrowth. Tissue response to covered and uncovered stents was compared in dogs. Stents were surgically placed in the bile ducts of 22 mongrel dogs through the sphincter of Oddi. Either a silicone-covered stent or an uncovered stent was inserted. Liver function test values remained normal throughout a 1- or 3-month study. Necropsy revealed that all ducts were unobstructed. Bile duct histologic examination revealed mild-to-moderate cellular infiltration in all animals. Mucosal hyperplasia was more marked in the animals with uncovered stents and the bare wires became deeply embedded in bile duct epithelium, whereas the wires of covered stents did not. We conclude that covered stents are well tolerated by the canine bile duct. These results suggest that such stents may be removable, making self-expanding metal stents an appropriate treatment for both benign and malignant biliary strictures.

Cystic duct anatomy: an endoscopic perspective.

Knowledge of the junction of the cystic and common hepatic duct is essential for endoscopic management of biliary tract disease. The cystic and common hepatic ducts were evaluated retrospectively in cholangiograms obtained for a variety of indications in 524 persons. The cysticohepatic junction was adequately visualized in 70%. Medial junctions were noted in 18% and a spiral configuration in 32%, both more common than reported. An 11% occurrence of parallel duct systems was less frequent than expected. In 10% of patients, the cystic duct entered the hepatic duct in the distal third of the extrahepatic biliary tree. The importance of understanding this anatomy is illustrated with selected cases of therapeutic biliary endoscopy and laparoscopic cholecystectomy complications. Suggestions are made for improving performance in this area.

Results of a multicenter trial using a mechanical lithotripter for the treatment of large bile duct stones.

A prospective, uncontrolled trial of the use of a prototype mechanical lithotripter was performed in 116 patients at nine centers. Standard endoscopic approaches had failed to remove all stones, primarily because of large size (80% of patients). For 92% of patients, common bile duct stones were successfully captured and fragmented following the use of this lithotripter. The frequency of pancreatitis and hemorrhage was no greater than with standard endoscopic retrograde sphincterotomy, and complications unique to lithotripter use were not noted. For endoscopists skilled in therapeutic duodenoscopy, this modality should be considered in management of common bile duct stones refractory to standard techniques.

Bipolar electrosurgical sphincterotomy.

We tested a newly developed bipolar sphincterotome. Monopolar and bipolar sphincterotomes were employed to cut small bowel smoothly and hemostatically. The bipolar instrument required 17.1 watts while the monopolar required 29.2 watts; these values are significantly different at p = 0.005. Bipolar sphincterotomies were performed via open surgical access on eight dogs. The animals were allowed to recover and were followed for 6 weeks. There was no evidence of stenosis or common duct dilation at autopsy, and serum alkaline phosphatase and bilirubin were within normal limits. Both sphincterotomes were used to cut tissue in vitro and histological examination displayed no evidence of thermal injury at the return electrode site of the bipolar sphincterotome. The lower power levels required by the bipolar sphincterotome may decrease procedure complications.

The interaction between electrosurgical generators, endoscopic electrodes, and tissue.

Endoscopic monopolar and bipolar devices were compared during cutting and coagulation. It was observed on appropriate animal models that the initial resistance (impedance) values recorded correspond to the normal tissue impedance at the electrode. The subsequent impedance values increase 25 to 50 ohms for the coagulator which relates to tissue desiccation and for the cutting electrodes the impedance increases greater than 1000 ohms during the arcing process. At similar power settings, typical monopolar generators produce maximum power at 300 to 500 ohms while typical bipolar generators produce maximum power at 25 to 100 ohms. With impedances greater than 1000 ohms, monopolar generators are capable of higher power output than are bipolar generators. Since cutting is a high impedance process, bipolar cutting electrodes do not perform as intended with typical bipolar generators. Therefore, bipolar cutting electrodes should be employed with a monopolar generator or a generator designed specifically for their use.

Thermal ablation of the gallbladder.

Gallbladder ablation by means of injection of hot contrast medium was attempted in 13 dogs. Room temperature contrast medium was injected into the gallbladders of two additional dogs (controls). After midline laparotomy was performed to expose the gallbladder, temperature probes were placed in the liver adjacent to the gallbladder, and on the surface and in the lumen of the gallbladder. A 7-F catheter with multiple side holes was placed into the gallbladder. The cystic duct was clamped during the procedure. After injection of boiling contrast medium, the mean temperature in the gallbladder lumen was 80 degrees C; in the adjacent liver, 43.5 degrees C; and on the gallbladder surface, 45.8 degrees C. After the procedure, the cystic duct was unclamped, temperature probes and catheter were removed, and the laparotomy was closed in standard fashion. In the hot contrast medium group, one dog each was sacrificed at 2, 4, 8, and 12 weeks, and at 6 months. Six animals were sacrificed at 1 year. The gallbladder was completely ablated in 11 of 13 animals in the hot contrast medium group. One dog was sacrificed at 8 days because of bile leakage, and another was sacrificed at 17 days because of gallbladder rupture. The two control animals were sacrificed at 12 and 13 weeks, and their gallbladders were normal at that time.

In vivo evaluation of monopolar versus bipolar electrosurgical polypectomy snares.

The energy required and tissue damage in bipolar and monopolar polypectomy snares were compared in a canine model. The bipolar snare required an average of 34 joules of energy, whereas the monopolar snare required 228 joules to cut the same diameter of gastric mucosa tended into a polypoid structure (p = 0.0005). The reduced energy delivered to the tissue from the bipolar procedure resulted in only 32% average depth of damage to the underlying gastric wall, whereas the monopolar procedure caused an average 69% (p = 0.001). Surgically created polyps required 247 joules and 69 joules for corresponding monopolar and bipolar polypectomy (p = 0.001). The decreased energy required and the correspondingly reduced damage caused to the underlying bowel wall by the bipolar snare should reduce the incidence of perforation and post-polypectomy syndrome. The bipolar snare completes a local circuit about the snare, eliminating the return electrode and, consequently, the possibility of any return electrode burns. The bipolar snare thus provides an added safety margin during polypectomy.

A new mechanical lithotripter for the treatment of large common bile duct stones.

A prospective uncontrolled multi-center trial of a prototype mechanical lithotripter was performed in 30 patients with common bile duct calculi. Standard endoscopic sphincterotomy had failed to remove all stones, primarily because of large size (26 patients). Stone size ranged from 13 to 35 mm. Forty-three of 45 stones (97%) were successfully captured, fragmented, and extracted with this newly designed mechanical lithotripter. The overall success rate of 93% using this simple and inexpensive modality compares favorably with other methods under investigation for the treatment of common bile duct stones not amenable to routine endoscopic measures.

Choledochal cyst: findings on cholangiopancreatography with emphasis on ectasia of the common channel.

Choledochal cyst is a congenital malformation of the biliary tree that is unusual but by no means rare. During a 13-year period, we encountered eight patients with choledochal cysts who were evaluated with cholangiopancreatography. All of our cases showed an anomalous union of the pancreatic duct and common bile duct, resulting in a long common channel. Review of cholangiopancreatograms also showed ectasia of the common channel in six of the eight patients. Mean length of the common channel, corrected for magnification, was 26 mm (normal, less than 15 mm). The mean corrected diameter of the common channel was 7 mm (normal, 3-5 mm). We conclude that ectasia of the common channel is an important additional radiographic observation in the diagnosis of choledochal cyst. This observation has not been emphasized before.

Effects of biliary obstruction on hepatic clearance of bacteria.

High surgical mortality in patients with obstructive jaundice and sepsis have been attributed to reticuloendothelial system (RES) depression. The purpose of this study was to clarify the effects of mechanical biliary obstruction on RES clearance of pathogenic bacteria by comparing the phagocytic index (K) with the directly measured hepatic uptake of indium 111-labeled bacteria injected into the portal vein of normal dogs and dogs with partial (PBO) or complete biliary obstruction (CBO). No significant difference was observed between the K in normal dogs (0.19 +/- 0.08; n = 6) and that in dogs with PBO (0.24 +/- 0.06; n = 5) or CBO (0.21 +/- 0.03; n = 4). There was no significant difference in uptake of radiolabel by the liver among the three groups of dogs. In our model, biliary obstruction had no effect on hepatic RES function and may not represent a significant determinant of mortality in patients with obstructive jaundice.

Pancreatic pseudocysts: clinical and endoscopic experience.

Records of 51 patients with proven pancreatic pseudocyst (PC) were retrospectively reviewed to assess clinical and endoscopic variables. Thirty-nine had surgery after preoperative endoscopic retrograde cholangiopancreatography (ERCP), six patients had ERCP only, and six patients had surgery without prior ERCP. Forty-two pancreatograms were obtained, and all were abnormal. PC communication with the pancreatic duct was present in 29 and ductal obstruction downstream from the PC was shown in 11 studies. Thirty-five cholangiograms were obtained and 19 were abnormal, including ductal narrowing in 16 and biliary calculi in three. PC contents were cultured intraoperatively in 29 patients, and 17 were positive. PC infection was highly correlated with the incidence of recurrent hospitalizations and with PC recurrence. PC infection did not occur significantly more often in patients with communicating PC or in those with preoperative ERCP. Factors that did not influence outcome included PC size, multiplicity, anatomic location, and PC communication with the pancreatic duct. Results from both ERCP and culture of PC contents add significantly to our knowledge of PC disease.

Spontaneous passage of glass beads from the canine gallbladder: facilitation by sphincterotomy.

To investigate the mechanism by which ablation of the sphincter of Oddi prevents gallstone formation, we assessed passage of glass beads out of the gallbladders of dogs with sphincterotomy and sham sphincterotomy. One month after bead implantation, dogs with an intact sphincter passed 52%, 26%, 22%, 10%, 0%, and 0% of beads with diameters of 2, 3, 4, 5, 6, and 8 mm, respectively. For the same respective bead diameters, dogs with a sphincterotomy passed 90%, 90%, 88%, 75%, 75%, and 42% of beads (p less than 0.05 for all bead diameters). No beads were in the common bile duct of any dog. In separate dogs studied by cholescintigraphy, sphincterotomy significantly increased gallbladder ejection fraction from 0.46 to 0.76 (p less than 0.01). In addition, sphincterotomy significantly lowered resting gallbladder volume from 24.4 to 15.8 ml (p less than 0.025) and lowered cholecystokinin-stimulated gallbladder volume from 13.3 to 5.9 ml (p less than 0.025). These data indicate that even with an intact sphincter, small solids can pass from the gallbladder and into the duodenum. Sphincterotomy facilitates passage of solids, apparently by general improvement in gallbladder emptying. Facilitated passage of crystals, microliths, or small stones seems the most likely explanation for prevention of gallstone formation by sphincterotomy.

Effect of bombesin and gastrin-releasing peptide on canine sphincter of Oddi.

This study reports the effects of bombesin and gastrin-releasing peptide (GRP) on the canine sphincter of Oddi using a method that allows repeated cannulation of the biliary sphincter in the unanesthetized animal through a Thomas cannula placed opposite the biliary papilla. Immediately after intravenous administration of bombesin or GRP, phasic sphincter contractions disappeared, basal sphincter pressures fell, and common bile duct pressures rose. Because bombesin releases cholecystokinin (CCK) and CCK resulted in a similar pattern to that of bombesin, the bombesin effect on the sphincter of Oddi may have been secondary to CCK's effect on the sphincter. To test if the bombesin effect on the sphincter of Oddi was due to the release of CCK, we blocked CCK release by administration of somatostatin, having first established that somatostatin blocked endogenous CCK release in our animal model by use of an intraduodenal infusion of lipid. Exogenous administration of bombesin failed to alter sphincter of Oddi or common bile duct pressures in dogs treated with somatostatin. Somatostatin did not, however, block CCK's effect on gallbladder contraction, since exogenous administration of CCK after somatostatin injection resulted in the pressure changes in the biliary tree typical of CCK-induced gallbladder contraction. Thus bombesin administration appears to result in sphincter relaxation and gallbladder contraction by the release of endogenous CCK rather than by a direct effect. The increase in common bile duct pressures was due to gallbladder contraction, since this rise in pressure was abolished by cholecystectomy. The peptide effect on sphincter contraction and basal sphincter pressure were unaffected by cholecystectomy.

Partial biliary obstruction caused by chronic pancreatitis. An appraisal of indications for surgical biliary drainage.

This paper presents a retrospective review of 38 patients with intrapancreatic bile duct strictures secondary to chronic alcoholic pancreatitis. The strictures were identified by endoscopic retrograde cholangiopancreatography (ERCP). All patients with pancreatic cancer and gallstone pancreatitis were excluded. The mean alkaline phosphatase and total bilirubin values were 344 +/- 57 IU/dl and 4.4 +/- 0.7 mg/dl, respectively. The mean stricture length was 3.9 +/- 0.5 cm, and the mean common bile duct (CBD) diameter was 1.8 +/- 0.2 cm. The degree of bilirubin and alkaline phosphatase elevation did not correlate with stricture length or the severity of bile duct dilatation. Eighteen of the 38 patients received surgical biliary drainage (BD) as part of their initial therapy, and 20 patients did not. Liver function tests, intrapancreatic stricture length, and the degree of proximal CBD dilation were comparable in these two groups. Patients not undergoing BD did well clinically as only one patient required BD over an average follow-up period of 3.8 years. In conclusion, bypass of these strictures is usually unnecessary, and most patients may be safely treated without operation.