Rectal arterio-venous malformation (AVM) with bleeding of an internal hemorrhoid

A 38-year-old male with no past history of illnesses visited the out-patient clinic of Nerima Hikarigaoka Hospital complaining of dizziness and persistent anal bleeding. There was a significant anemia on a blood test and colonoscopy showed a thrombus in a markedly swollen internal hemorrhoid. Contrast-enhanced computed tomography (CT) showed a poorly demarcated area with early face enhancement on the right side of the rectum and anal canal. Based on these findings, an arterio-venous malformation (AVM) of the rectum was suspected. Abdominal angiography showed abnormal vessels receiving a blood supply from the bilateral superior rectal arteries. We suspected that the AVM in the rectum was the cause of the hemorrhage from the internal hemorrhoid, and therefore performed embolization of the AVM. Thereafter, the hemorrhage from the internal hemorrhoid stopped completely and the anemia improved to the normal level, without the need for treatment for the internal hemorrhoid. Colonoscopy performed 6 months after embolization showed shrinkage of the internal hemorrhoid. To the best of our knowledge, there are no reports stating a relationship between rectal AVM and internal hemorrhoids. However, we consider that contrast-enhanced CT can be used to detect vessel abnormalities related to severe bleeding of the internal hermorrhoids in patients with internal hemorrhoids and severe anemia.