Incidental Left Portal Branch Aneurysm in a Patient with Hepatosplenomegaly: A Case Report and Review of the Literature

Introduction: Portal vein aneurysms (PVA) are rare vascular anomalies, with intrahepatic branch involvement being significantly less common than extrahepatic forms. They are often detected incidentally but can mimic other cystic liver lesions. Case Presentation: A 60-year-old male presented for evaluation of BI cytopenia and hepatosplenomegaly. Transabdominal ultrasound revealed a coarse liver texture and a dilated main portal vein (15 mm). An anechoic, saccular lesion measuring 22 mm was identified in the Rex recess, communicating with the left portal branch (9 mm). Color Doppler demonstrated turbulent "yin-yang" flow, confirming a left portal branch aneurysm. No elevated liver enzymes were noted. The patient was managed conservatively with serial imaging surveillance. Conclusion: Color Doppler is mandatory for the evaluation of all cystic-appearing liver lesions to exclude vascular anomalies. Precise identification of a portal vein aneurysm is critical to prevent the potentially fatal complication of accidental percutaneous biopsy and to guide appropriate non-operative management.