Mixed type I and II choledochal cyst: a new clinical subtype?

Traditionally, choledochal cyst (CC) is classified into five types according to Todani's classification. Of 356 cases of CC treated at our institute since 1965, we experienced four cases of mixed type I and II choledochal cyst (MTCC). The incidence of MTCC was 1.1%. All four patients had a fusiform common bile duct (CBD) with a diverticulum originating from the mid-portion of the CBD. The cystic duct drained into the right side of the diverticulum. All had pancreaticobiliary malunion (PBMU). All presented with recurrent abdominal pain. MTCC was suggested on ultrasonography or computerized tomography and confirmed by endoscopic retrograde cholangiopancreatography (three cases) or magnetic resonance cholangiopancreatography (one case). Age at surgery ranged from 3 to 12 years. All had hepaticoenterostomy, and total excision of the CC/diverticulum/gallbladder. There were no complications and all cases are currently well. In all cases, histopathology showed that the wall of the diverticulum was identical to the CBD. Although the incidence of MTCC is very low, pediatric surgeons should be aware of it as a new subtype of CC. Based on our experiences and a review of the literature, we suggest that its etiology does not affect treatment because the surgical management of choice is the same as for type I CC.