Possible causes of bloody bowel movements include anal fissures, diverticular disease, petptic ulcers, esophageal disorders and angiodysplacia, according to WebMD. Polyps and cancer also sometimes cause bloody stools, although colorectal cancer frequently causes minimal bleeding that cannot be seen by the naked eye.
An anal fissure is a tear or cut in the tissue surrounding the anus often caused by passing large or especially hard bowel movements, states WebMD. Anal fissures can sometimes cause significant pain.
Diverticula are pouches that extend out from the wall of the colon, notes WebMD. When they become infected and bleed, blood can appear in bowel movements. Andiodysplacia is a disorder in which weakened blood vessels lead to excessive bleeding.
To diagnose bloody bowel movements, doctors typically review the patient's medical history and then conduct a physical exam, states WebMD. Tests used to help doctors determine the cause of bloody stool include nasogastric lavage, esophagogastroduodenoscopy, which is a scope that reaches from the esophagus to the duodenum, colonoscopy, enteroscopy and radionuclide scanning. A fecal occult blood test checks for hidden blood in stool that cannot be detected visually.
Treatment for bloody bowel movements depends on the cause of the bleeding, explains WebMD. Polyps, cancer and diverticulitis may require surgery, whereas eating a high-fiber diet to prevent constipation can alleviate and prevent anal fissures.