Residual biliary stones: do we need peroral cholangioscopy?

We read with interest the recent study by Lee et al. regarding the use of direct peroral cholangiography for the management of residual biliary stones after mechanical lithotripsy [1]. The management of residual stones after mechanical lithotripsy indeed remains a challenge. Traditionally, residual stones are detected indirectly by occlusion cholangiography with balloon or basket. Recent studies have noted that cholangioscopy is an alternative for detecting residual biliary stones [1] [2] [3]. There are a number of technical differences between cholangiography and cholangioscopy, but the major difference lies in the ability of the latter technique to provide direct visualization of a stone. There are several factors related to non-detection of residual stones on cholangiography.

First, if a stone is insufficiently enhanced it may not be disclosed in the image. Inadequate concentration of contrast medium, mostly due to overenhancement of the biliary tract, does not allow proper visualization of the stone. The full-strength concentration of contrast medium of 50 % – 100 % (iodine 150 – 300 mg/mL) is usually optimal for opacifying the pancreatic duct or stricture lesion of the biliary tract. In a dilated common bile duct, a contrast medium concentration of 20 % – 25 % would result in better cholangiography [4]. Also, the presence of a large volume of bowel gas may mask a stone. These factors can be overcome by adequate setting of contrast medium concentration and appropriate patient positioning.

The second factor that can result in non-detection of residual stone on cholangiography is the location. Stone fragments can move upstream to intrahepatic ducts or to the distal common bile duct, particularly with a pouch, after mechanical lithotripsy. In such cases, adequate contrast concentration in the biliary system and careful examination of cholangiograms may be helpful.

The third factor is the size and composition of stones. The composition of stones depends on various conditions. Itoi et al. demonstrated that large size of bile duct stones, juxtapapillary diverticulum, and fragmentation procedure were significantly related to the presence of residual stones [2].

For intrahepatic stones, an ultraslim endoscope that can be used with a relatively larger diameter intrahepatic duct may not be capable of reaching the branches of intrahepatic ducts. Properly performed balloon occlusion cholangiography would be a better choice for intrahepatic duct stones. In addition, appropriate endoscopic retrograde cholangiopancreatography (ERCP) accessories for stone extraction, such as the flower-type basket or wire-guided flower-type basket, are capable of retrieving small biliary stones or intrahepatic duct stones. Additional therapeutic procedures such as peroral cholangiography, may not be cost-effective.

In the event of pneumobilia (due to previous sphincterotomy or choledochal – duodenal fistula), balloon occlusion cholangiography is possible with the patient’s head placed in a downward position and the legs raised. Occlusion cholangiography can be performed to detect small lesions or stones. In this procedure, a retrieval balloon is placed above the biliary hilum and air is suctioned from the biliary tree after injection of contrast. The fully inflated balloon can then be pulled to the orifice of the common bile duct.

The patients enrolled in the aforementioned study by Lee et al. had residual stones up to 9 mm in diameter. It is possible that the authors did not demonstrate adequate cholangiography for residual stones. Furthermore, most of the residual stones might have been dispersed after a complete endoscopic sphincterotomy, which results in complete destruction of the sphincter muscle.

Most published data suggest that alternative interventions (cholangioscopy or intraductal ultrasonography) detect residual stones better than balloon occlusion cholangiography by ERCP [1] [2] [3] [5]. There is a limited number of studies on cholangiography, though it is clear that great care must be taken to ensure that cholangiography procedures are properly performed. If the relative costs and benefits are weighed, adequate evaluation with occlusion cholangiography and complete sphincterotomy may be the best strategies for residual stones, particularly in diffused or focal stricture of the common bile duct. The major role of cholangiography for residual stones may be in the application of an additional fragmentation procedure for difficult stones.

• References

• 1 Lee YN, Moon JH, Choi HJ et al. Direct peroral cholangioscopy using an ultraslim upper endoscope for management of residual stones after mechanical lithotripsy for retained common bile duct stones. Endoscopy 2012; 44: 819-824
• 2 Itoi T, Sofuni A, Itokawa F et al. Evaluation of residual bile duct stones by peroral cholangioscopy in comparison with balloon-cholangiography. Dig Endosc 2010; 22: S85-S89
• 3 Moon JH, Ko BM, Choi HJ et al. Direct peroral cholangioscopy using an ultra-slim upper endoscope for the treatment of retained bile duct stones. Am J Gastroenterol 2009; 104: 2729-2733
• 4 Mishkin D, Carpenter S, Croffie J et al. ASGE Technology Status Evaluation Report: radiographic contrast media used in ERCP. Gastrointest Endosc 2005; 62: 480-484
• 5 Ohashi A, Ueno N, Tamada K et al. Assessment of residual bile duct stones with use of intraductal US during endoscopic balloon sphincteroplasty: comparison with balloon cholangiography. Gastrointest Endosc 1999; 49: 328-333