Biliary Metal Stent as a Nidus for Bile Duct Stone

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Abstract

INTRODUCTION

Bile duct stones can be classified as either primary or secondary. Secondary stones originated in the gallbladder and migrate into the common duct. Primary stones, formed de novo within the bile duct, are less frequently encountered. A variety of factors may contribute to the formation of primary duct stones. Stasis is an important contributor and can result from stricture or other causes of obstruction, including foreign bodies. A nidus is important for the formation of both primary and secondary stones.

The formation of biliary calculi around a migrated surgical material after cholecystectomy is unusual cause of choledocholithiasis. Several cases of recurrent stone formation caused by a surgical material as a nidus have been reported. In one study, 30% of recurrent stones in the common duct after cholecystectomy were reported to contain nonabsorbable suture materials in the center of the stone, serving as a nidus^1,2). We describe one case in which a migrated metal stent might have been served as a nidus for common duct stone formation. The diagnosis was confirmed by ERCP, the stone was successfully removed with endoscopic therapy.

CASE

A 52-year-old woman was admitted to our institute with abdominal pain in the right upper quadrant and anorexia for a few days. In 1995, she had undergone a lithotripsy using a percutaneous cholangioscopy (PTCS) because of intrahepatic bile duct stones. A covered self-expandable metal stent (polytetrafluoethylene [PTFE] material) had also been inserted in the stricture site of left main intrahepatic bile duct to avoid cholangitis caused by clogging and recurrent intrahepatic bile duct stone. The patient had been symptom free for 6 years following the above mentioning procedures. Six years later, she developed abdominal pain in the right upper quadrant associated with an elevated serum level of aminotransferase and alkaline phosphatase (aspartate aminotransferase, 56 IU/L [normal, 0 to 37 IU/L]; alanine aminotransferase 45 IU/L [0–41 IU/L]; alkaline phosphatase, 643 IU/L [53–128 IU/L]). Ultrasonographic examination of the abdomen revealed marked dilation of extrahepatic bile duct and both intrahepatic ducts. On abdominal ultrasound examination, a large echogenic density (20×48 mm) was demonstrated in the common bile duct, which casted a shadow (Figure 1). ERCP revealed the dilated extrahepatic bile duct and left intrahepatic bile duct and the presence of a large elongated freely mobile filling defect suggestive of common bile duct stone containing metal mesh in the distal common bile duct (Figure 2). There was no previously observed stricture in the left intrahepatic bile duct. After successful endoscopic sphincterotomy, mechanical lithotripsy was performed because of the large size of the stone. The removed stone was soft and dark brown in color (Figure 3A), with metal stent extruding from the ampulla of Vater along with common bile duct stone fragments (Figure 3B). After complete removal of the stone, the serum level of hepatic enzymes returned to normal and the patient has remained asymptomatic.

Figure 1.

Ultrasonographic examination of the abdomen revealed marked dilation of extrahepatic bile duct and both intrahepatic ducts and a large echogenic density (20×48 mm) was demonstrated in the common bile duct, casting a shadow

Figure 2.

A & B. ERCP demonstrates dilated extrahepatic bile duct and left intrahepatic bile duct. Note a large elongated filling defect with a central metal stent in the extrahepatic bile duct.

Figure 3.

The picture shows the exposed metallic stent conglomerated with the fragments of stone (left) and the distorted covered metal stent with polytetrafluoethylene [PTFE] material after washing (right).

DISCUSSION

Broad spectrum of foreign materials has been found to trigger the formation of brown stones. A nonabsorbable black silk suture from previous biliary surgery is a typical example. Ban et al.⁴⁾ reported that the incidence of stone formation in the biliary tree around organic substances, such as silk or other ingested foreign materials, was 82% of the recurrent stone formation around a foreign body. Metals and metallic fragments were found in the biliary tree in these cases, but only 33% of the inert foreign bodies were found to have caused the stone formation.

The formation of biliary tract stones around surgically introduced foreign material has been well documented. It is reported that 30% of recurrent stones after cholecystectomy contained nonabsorbable suture material in their nuclei⁵⁾. In a case reported in 1897, silk sutures served as the nidus for gallstone formation after cholecystectomy⁶⁾. The first case of a surgical clip or a staple causing stone formation was reported in 1979⁷⁾. The first case of successful endoscopic therapy of a metallic clip forming the nidus of a common duct stone was reported in 1982⁸⁾. In more recent reports, metallic surgical clips migrated into the biliary tract and acted as a nidus for stone formation^8–10). Biliary stasis and bacterial overgrowth resulting in bacterial degradation of bile were contributing factors in those cases¹¹⁾. Prochazka et al.¹²⁾ reported that they found surgical suture materials in four patients out of 25 who had undergone cholecystectomy (13.8%). They proposed that the foreign materials found in the concrements of the patients must have been originated from surgical sutures of previous operations. The surgical sutures, because of the sequestration of non-absorbed material into the biliary duct, had acted as crystallization nuclei where part of the bile was precipitated and lodged, leading to stone formation. Our case differs from those previously reported in that the patient developed recurrent stones in the common bile duct after cholecystectomy containing foreign material in the center of the stone. Our case did not have a history of previous operation; we had inserted metal stent with polytetrafluoethylene [PTFE] material in order to treat the stricture in the proximal part of left intrahepatic bile duct. After complete removal of intrahepatic duct stones 6 years ago, neither of the stricture or stones in the left intrahepatic bile duct was found any more, but only mild dilatation of left intrahepatic bile duct was seen at endoscopic retrograde cholangiography. Many questions remain as to optimal endosc

The cases of common bile duct stones formation after metal stent insertion in the stricture of intrahepatic bile duct have been rarely reported. We reported one case in which a migrated metal stent from left intrahepatic bile duct might have been served as a nidus for common duct stone formation, which was successfully removed after endoscopic sphincterotomy and mechanical lithotipsy with basket. Martinez et al.¹³⁾ reported that eleven of the 14 reported cases of migration of surgical clips into the common bile duct hade been successfully managed with endoscopic therapy. Endoscopic sphincterotomy is the procedure of choice for removal of common duct stones post cholecystectomy. Compared with surgery, it is less invasive, less expensive and requires a shorter hospital stay. The presence of a metallic stent forming the nidus of the stone does not interfere with successful endoscopic extraction after sphincterotomy.

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