A very rare case of highly probable retroperitoneal fibrosis leading to extrahepatic portal obstruction is described. The patient was a 44-year-old woman with right pleural effusion and splenomegaly. Computed tomography indicated a large accumulation of soft tissues in the retroperitoneum, and abdominal angiography showed extensive portal obstruction. A twenty-year-long abuse of analgesics is suspected to have caused the retroperitoneal fibrosis.