[A case of ischemic proctitis caused by impaired venous blood flow 11 months after surgery for sigmoid colon cancer].

A Japanese male in his 50s was presented to our hospital with the chief complaint of positive fecal immunochemical test. He had a history of hypertension. He underwent colonoscopy and was diagnosed with sigmoid colon cancer. He also underwent laparoscopic sigmoid colectomy with D3 lymph node dissection for sigmoid colon cancer. The inferior mesenteric artery and inferior mesenteric vein were amputated at the root of the vessels. The patient received adjuvant chemotherapy and was recurrence-free. Eleven months after the surgery, lower abdominal pain during defecation appeared. Contrast-enhanced computed tomography (CT) and colonoscopy showed marked rectal mucosal edema and increased fatty tissue density (dirty fat sign) around the anorectal side of the anastomosis. Intestinal blood flow was maintained. There were many fine blood vessels around the rectal wall, and the amputated distal part of the superior rectal artery was retrogradely contrasted. Amputated superior rectal artery and superior rectal vein were dilated than before. Colonoscopy revealed mucosal redness, edema, and easy bleeding on the anorectal side of the anastomosis. Abdominal contrast-enhanced 3D-CT showed increased arterial blood flow and increased fine blood vessels around the rectal wall. It suggested the presence of an arteriovenous fistula and venous congestion. Conservative treatment with total parenteral nutrition and prednisolone infusion did not improve the patient's condition, and a colostomy was performed. After colostomy, the pain improved, and the CT scan of the abdomen showed improvement in arterial blood flow and venous congestion. Colostomy was closed after 10 months. There has been no relapse since the closure of the colostomy. There are few reports on ischemic proctitis on the anorectal side of the anastomosis after colon cancer resection due to impaired venous blood flow.