In recent years, the use of ultrafine choledochoscopy has gradually increased in the treatment of cholelithiasis. However, stone incarceration and residual spasm of the sphincter of Oddi may be inevitable when an ultrafine choledochoscope is used alone.

To investigate the safety and feasibility of ultrafine choledochoscopy combined with low-dose atropine in the treatment of Oddi intersphincter stones.

Seventeen patients with Oddi intersphincter stones were retrospectively analyzed. The perioperative clinical data and follow-up information were collected.

Among the 17 patients, 3 were male and 14 were female. The mean age was 40.6 ± 13.9 years, and the mean diameter of the common bile duct was 7.8 ± 1.3 mm. All patients successfully underwent Oddi intersphincter stone removal using a combination of ultrafine choledochoscopy and low-dose atropine. No serious complications, such as postoperative hemorrhage, pancreatitis or bile leakage occurred in the 17 patients. During the one-year follow-up, none of the patients experienced stone recurrence.

Ultrafine choledochoscopy combined with low-dose atropine is safe and feasible for the treatment of Oddi intersphincter stones.

Bile is secreted continuously, although at various rates, from the liver into the biliary tree; whether bile is then diverted into the gallbladder or the duodenum depends on the relative resistance to flow mainly determined by the contractile state of the gallbladder and the choledochoduodenal junction. The resistance of the sphincter of Oddi is considered the principal factor in the regulation of the intracholedochal pressure and, therefore, of the common bile duct-gallbladder pressure gradient; however, filling of the gallbladder may also take place after total sphincterotomy. During late phase II of the interdigestive period intragallbladder pressure increments favour flow of a small amount of bile into the bile duct and, through the sphincter of Oddi, into the duodenum. During phase III of the interdigestive period maximal frequency of sphincter of Oddi phasic contractions blocks bile flow into the duodenum. After a meal tonic active contraction of the gallbladder causes an increase of the intraluminal pressure followed shortly by volume reduction of the viscus and outflow of bile accompanied by an intracholedochal pressure increment. Gallbladder hypotonia is a relevant factor in the pathogenesis of gallbladder stones. The gallbladder acts as a reservoir, since intracholedochal pressure is higher after than before cholecystectomy, and this may explain post-cholecystectomy choledochal dilatation and biliary pain by obstructed bile flow due to either stenosis or dyskinesia of the sphincter of Oddi.