A 61-year-old woman presented to our department with repeated upper abdominal pain for one year without vomiting, jaundice, chills, or fever. The onset of pain was initially every 2–3 weeks but had recently increased to every 1–2 weeks. During this period, she was diagnosed and treated for chronic nonatrophic gastritis at the gastroenterology clinic several times, but her pain was not relieved. No special procedures were performed prior to admission, except for abdominal ultrasonography (USG) at a local hospital. The patient did not have any history of addiction to nicotine or alcohol, weight loss, hypertension, cancer in the family, diabetes, nor did she have a previous surgery. No abnormalities were found during a physical examination. The following laboratory tests were conducted after admission, including electrolyte levels, routine blood tests, tumor marker levels and liver and kidney function. An abnormal WBC value was detected of 11.78 × 10¹²/L [reference range (RR) is 4.0–9.0 × 10¹²/L], neutrophilic granulocyte percentage was 0.77 (RR, 0.5–0.7). Abnormal liver function indicators were as follows: alanine aminotransferase (ALT) concentration of 353.03 IU/L (RR, 5–40 IU/L), aspartate aminotransferase (AST) concentration of 55.48 IU/L (RR, 8–40 IU/L), γ-Glutamyl-converting enzyme (γ-GT) concentration of 394.48 IU/L (RR, 8–57 IU/L), leucine aminopeptidase concentration of 123.77 IU/L (RR, 10–40 IU/L), glutamate dehydrogenase concentration of 56.31 IU/L (RR, 2–10 IU/L), and alkaline phosphatase concentration of 230.54 IU/L (RR, 30–120 IU/L). A measured bilirubin level, amylase level, lipase level, or tumor marker did not show any abnormalities. The immune globulin G4 level was also within normal ranges.

The patient completed relevant imaging examinations at our hospital. The deep location of the distal CCs and intestinal gas accumulation prevented USG from detecting the cyst at the end of the CBD but showed that the diameter of the CBD in the upper pancreas was slightly widened, with the widest part measuring 10 mm. The abdominal USG found that the pancreas had a normal shape with a smooth contour, homogeneous echogenicity, and no dilatation of the pancreatic duct. Abdominal CT and MRCP were arranged for the patient. MRCP showed a cystic structure (15 × 15 mm) in the distal CBD, suggestive of type III CCs (Fig. 1A) but failed to show the pancreaticobiliary duct junction union. The patient consented to undergo endoscopic retrograde cholangiopancreatography (ERCP) which revealed cystic findings compatible with Todani type III CCs (Fig. 1B) and an anomalous pancreaticobiliary duct junction (APBDJ) (Fig. 1C). During ERCP, the concentration of amylase in the bile at the end of CBD was 90,349 U/L. We determined the definitive diagnosis of type III CCs based on the patient’s medical history, signs, and symptoms, and auxiliary examination results. Duodenoscopy did not recognize the bulge but identified a flat, granular opening of the duodenal nipple in the duodenum (Fig. 1D). As a result, sphincterotomy was not appropriate and minimally invasive surgery was ordered for the patient.

After ERCP, serum amylase and urine amylase levels were both slightly elevated (161.7 U/L and 988 U/L, respectively) but abdominal USG showed no signs of pancreatitis. Laparoscopic surgery was performed when all parameters returned to a normal range and was used in combination with choledochoscopy to detect the lesion. The spherical cyst cavity had a honeycomb appearance under the choledochoscope, and the opening of the bile duct merged into the pancreatic duct (Fig. 1E). These observations were consistent with the ERCP results. Thus, laparoscopic cholecystectomy and Roux-en-Y hepaticojejunostomy were performed, and the proximal CBD was clamped to reduce the stimulation of bile to the cystic wall and limit the bile duct pressure (Fig. 1F). The patient’s postoperative serum amylase, urine amylase, and serum lipase parameters were within normal limits, and AST, ALT, γ-GT, and other indicators returned to a normal range within 5 days after surgery. Abdominal USG showed no signs of pancreatitis or abdominal effusion. Following the surgery, the patient recovered without complications and was discharged after seven days.

After 6 months, the patient returned for follow-up without abdominal discomfort, jaundice, nausea, vomiting, or other symptoms, and reexamination of the abdominal USG showed no dilatation of the biliary tree, a smooth pancreas, no dilatation of the pancreatic duct, and no signs of pancreatitis.