Although widely used in patients with biliary tract disease, ERCP procedures are challenging in the presence of anatomical abnormalities and even a skilled endoscopist can encounter technical difficulties when performing ERCP in patients with situs inversus. There have been only a few reports on ERCP in patients with situs inversus [2–6].

To increase the success rate, several techniques have been introduced for ERCP in patients with situs inversus [5]. In one technique, the endoscope is rotated 180° clockwise in the stomach; after entering the duodenum, the endoscope is again rotated 180° clockwise [7]. A similar technique involves turning the duodenoscope 180° clockwise in the stomach and using a rotating sphincterotome for cannulation [8]. These methods are performed in a familiar environment, as the position of the patient, the endoscopist, the endoscope machine, and the monitor are the same as usual. However, the techniques require a skilled endoscopist with abundant experience. In addition, if a loop is formed, it may be difficult to position the endoscope at the ampulla.

Another option is a “mirror image” method. The patient is usually placed in the right prone position because of the reversal of internal organs, and the endoscopist performs the procedure from the left side of the table. However, shortening the endoscope using a counterclockwise rotation in the mirror image method is inconvenient, as the endoscopist is required to manipulate the endoscope with the right hand. In addition, the position of the patient, endoscopist, the endoscopic machine, and the monitor must be changed. Alternatively, “inversed normal” ERCP can be performed with the patient in the prone position and the endoscopist on the right side of the table. The endoscope is advanced to the duodenum by following the lesser curvature without rotating the endoscope. In addition, when there is axis malalignment, endoscopic papillary balloon dilation (EPBD) can be relatively easy to perform once deep cannulation is accomplished. EPBD with or without endoscopic sphincterotomy (EST) is an alternative method to EST alone for stone removal.

We present an unusual case of CBD stones in a patient with situs inversus. Successful ERCP was performed using two different techniques. Specifically, we used two different modified twist methods. In the first ERCP, counterclockwise rotation was used to insert the endoscope with relative ease. The endoscope was fully rotated once. However, cannulation was difficult because the ampulla was on the right side of the screen. In the second ERCP with clockwise rotation, a second rotation was not performed. Cannulation was easily performed, as the ampulla was located at the center of the screen, slightly to the left. However, insertion of the endoscope was relatively difficult. The methods have not standardized, but show that an appropriate technique can be selected according to the patient’s position, loop formation and air volume.