Rare origin of the right inferior phrenic artery from the anterior inferior pancreaticoduodenal artery in a patient with hepatocellular carcinoma.

The inferior phrenic arteries show considerable variation in their origins. We describe a rare origin of the right inferior phrenic artery (RIPA) from the anterior inferior pancreaticoduodenal artery (AIPDA) in a patient with ruptured hepatocellular carcinoma (HCC), identified by contrast-enhanced computed tomography (CT) and angiography, and discuss its anatomical and clinical significance. A woman in her 80s underwent emergency transcatheter arterial embolization for ruptured HCC. Preprocedural contrast-enhanced CT did not identify the origin of the RIPA at its usual sites but suggested that it arose from the superior mesenteric arterial system and provided additional supply to the HCC, which was predominantly supplied by the right hepatic artery. Right hepatic arteriography demonstrated tumor staining and intratumoral contrast extravasation; however, a portion of the tumor remained unstained, suggesting extrahepatic arterial supply. The hepatic arterial branches were subsequently embolized with gelatin sponge particles. Superior mesenteric arteriography and selective inferior pancreaticoduodenal arteriography demonstrated that the RIPA arose directly from the AIPDA. Selective RIPA arteriography confirmed additional tumor supply from this vessel and demonstrated a branch arising from its anterior division that crossed the midline toward the left subdiaphragmatic region, consistent with a left inferior phrenic arterial branch. The RIPA was embolized with gelatin sponge particles, resulting in disappearance of tumor staining. The patient remained hemodynamically stable and was transferred the following day. The RIPA may rarely arise directly from the AIPDA. This case expands the known spectrum of inferior phrenic arterial origins and highlights the anatomical and clinical significance of recognizing this variation.