Rectal bleeding

Rectal bleeding describes bleeding from the anus or where blood is noticed on faeces or on the toilet bowl after sitting on the toilet. Rectal bleeding is reasonably common and in most cases the causes are not serious, however it is important to determine where the blood is coming from and what is causing the bleeding, in case there is a more serious condition.

What are the main causes of rectal bleeding?

Rectal bleeding can occur due to the following conditions...

  • Anal fissure (a small tear in the tissue of the anus)
  • Bowel infections
  • Bowel conditions (such as Crohn's disease, bowel/colon cancer, diverticular disease or other inflammation of the bowel eg ulcerative colitis)
  • Constipation
  • Haemorrhoids (also known as 'piles')
  • Polyps
  • Trauma of the rectum (eg from an injury or sexual assault)
  • Ulcers (of the stomach or duodenum)

Diagnosis of cause/s of rectal bleeding

A good indication of the cause of rectal bleeding is the colour of the blood. If it is bright red, the source of the blood is generally closer to the anus , if it is darker, or where the stools are tarry or black, the site of bleeding is likely to be higher in the bowel or in the stomach (stomach acids turn blood black).

When diagnosing the cause of the bleeding, your doctor will need access to your medical history and will need to do a physical examination and check any areas of tenderness or pain. He or she will also need to know if there have been any changes in going to the toilet or appearance of stools.

Some foods and medicine can cause stools to appear reddish (for example beetroot and iron supplements), so generally a blood test will be taken to check for blood count and detect any anaemia which may be caused by bleeding or blood loss. Severe blood loss is generally accompanied by cramping pain in the abdomen and weakness and dizziness. If this occurs you should seek immediate medical attention.

Other tests may be necessary to determine the cause of rectal bleeding. These may include...

  • Rectal examination
  • Anoscopy - an inspection of the anus and lower rectum
  • Sigmoidoscopy - examination of the lower bowel and rectum
  • Colonoscopy - examination of the whole colon (bowel)