Retrohepatic Gallbladder Masquerading as Hydatid Cyst in a Patient with Right Liver Agenesis.

Agenesis of the right liver is a rare congenital anomaly which can be associated with an ectopic gallbladder. Hereby, it is presented the case of a 39-year-old man investigated for right upper quadrant abdominal pain and diagnosed at computed tomography with a cystic liver mass initially considered as hydatid cyst. At laparotomy, it was discovered agenesis of the right liver and the presumed hydatid cyst was a retrohepatic gallbladder with lithiasis. Cholecystectomy was performed with an uneventful outcome. Reassessment of the computed tomography images by an experienced radiologist confirmed the intraoperative diagnosis. Although agenesis of the right liver with retrohepatic gallbladder is an exceptional appearance, surgeons should be aware of this anomaly because it can raise challenging issues of diagnosis and surgical planning during cholecystectomy.