Causes of rectal bleeding include hemorrhoids, inflammatory bowel disease, anal fissures, and anal or colon cancer, states Healthline. Crohn's disease, chronic constipation, radiation therapy and diarrhea can also cause rectal bleeding, according to Mayo Clinic.
Rectal bleeding involves bleeding from the lower colon or rectum, causing blood to pass from the anus, notes Mayo Clinic.
Hemorrhoids are inflamed and swollen veins in the anus and lower rectum, explains Mayo Clinic. They cause painless bleeding during bowel movements and anal itching or irritation. Hemorrhoids are the most common cause of rectal bleeding, according to Healthline.
Anal fissures are tears in the anus and the anal canal that cause pain, malodorous discharge and bleeding, notes MedicineNet. Causes include trauma to the anus, leukemia, anal cancer and tuberculosis.
As of 2015, it is unclear what causes inflammatory bowel disease, but a reaction of the immune system against its own intestinal tissue may be a contributing factor, says WebMD. Apart from intestinal bleeding, other complications associated with inflammatory bowel disease include malnutrition, obstruction of the bowel and rupture of the bowel.
Typical signs of rectal bleeding include red-tinged stool in the toilet bowl or red blood on toilet tissue, reports Healthline. Dark red blood may indicate bleeding in the small intestine, and bright red blood may indicate bleeding in the lower gastrointestinal tract. Black, tarry stools often indicate bleeding from the stomach.