A case of refractory proctosigmoiditis is reported in a 65-year-old female post-sigmoidectomy patient. She had bloody diarrhea and abdominal pain 2 years after sigmoidectomy, in which the inferior mesenteric vein was ligated close to the inferior mesenteric artery root during the lymph node dissection, while the inferior mesenteric artery trunk and the last branch of the sigmoid arteries was preserved. The biopsied specimen obtained by a fiber optic colonoscopy was diagnosed as proctitis. Antidiarrheals, 5-aminosalicylic acid and steroid enemas showed only limited therapeutic effects. An angiography revealed a mild degree of rectal artery dilatation and tiny venous angiogenesis detected on the delayed phase images. Because the inferior mesenteric vein had been ligated, collateral veins developed to drain the blood on the distal side of the anastomosis to bilateral internal iliac veins. The venous blood of the descending colon (oral side of anastomosis) drained to left colic vein. The cause of rectosigmoiditis was considered to be venous congestion due to the inferior mesenteric vein ligation. A rectosigmoidectomy with reanastomosis using a double-stapling technique was performed, and the patient was discharged without symptoms.