TAFRO syndrome is rare, and its pathophysiology remains unclear. We herein report the case of a 66-year-old man who presented at our emergency department with epigastric pain. Contrast-enhanced computed tomography (CT) showed high-density retroperitoneal panniculus with contrast enhancement. He was treated initially with a protease inhibitor and hydration, to little effect. Anasarca, thrombocytopenia, and renal dysfunction developed gradually, and TAFRO syndrome was diagnosed. He was treated successfully with prednisolone and cyclophosphamide, and subsequent CT findings showed improvement. Abnormal CT findings of the retroperitoneum may indicate the early stages of TAFRO syndrome before the presentation of typical ascites.