Type III choledochal cyst confirmed by aspiration and treated with endoscopic fenestration plus internal drainage: A case report

BACKGROUND Type III choledochal cysts (CCs) are extremely rare, and they present as dilatations and herniations of the end of the common bile duct into the duodenum. Moreover, type II CCs may be easily misdiagnosed as intraduodenal polyps or tumors. Thus, adequate differential diagnosis and selection of appropriate treatment are important. CASE SUMMARY A young man with a duodenal mass presented with 3-year intermittent abdominal pain and acute pancreatitis 3 days before hospitalization. After evaluation by magnetic resonance imaging and endoscopic ultrasonography, the duodenal papilla was pressed, and the bile flowed out slowly, which was speculated to be the cause of his symptoms. The lesion was punctured with a submucosal injection needle, and golden clear fluid was aspirated. Laboratory tests of the aspirate after 50-fold dilution revealed significantly elevated total bilirubin, direct bilirubin, amylase and lipase. Taken together, these findings confirmed that the lesion was a type III CC. The patient underwent fused surgical procedures. Fenestration plus internal drainage of the lesion was subsequently performed with a DualKnife. After drainage, the incision was sealed with tissue clips. During follow-up, the patient recovered well, and no abdominal pain symptoms or acute pancreatitis recurred. CONCLUSION Laboratory tests of cyst aspirates are beneficial for diagnosis, and endoscopic fenestration plus internal drainage works well to mitigate cysts.