Incidental Finding of Riedel’s Lobe of the Liver and Intrahepatic Cholangiocarcinoma

Riedel's lobe is a rare anatomical variant of the liver morphology with a downward tongue-like projection of the anterior edge of the right lobe. It is usually detected incidentally with abdominal imaging performed for other indications. We present a case where we found Riedel's lobe incidentally, with invasive adenocarcinoma arising from close proximity. A 64-year-old female came in with encephalopathy and was found to have a distended abdomen with tenderness. Imaging revealed a complex lobular mass in the right hepatic lobe with an elongated extension of the right lobe inferiorly consistent with Riedel's lobe. The differential considered was malignancy versus abscess. CT-guided biopsy revealed invasive adenocarcinoma consistent with intrahepatic cholangiocarcinoma, which was further supported by the presence of portocaval lymph nodes. Various studies have tried to establish an association between Riedel's lobe and the occurrence of cancer arising from the surrounding structures, primarily from liver or metastasis. This case report adds to the current literature when such an association is being studied.