Blood In The Stool Explained

The passage of blood per rectum is a very common symptom. It is often attributed by patients to haemorrhoids and they are a common cause of this symptom. However, there are other causes and it is important to know what the possible causes are and when and how to investigate this symptom further.

The type and amount of the bleeding as well as the age of the patient are important in initial assessment of the bleeding. There are many causes of rectal bleeding and the likely aetiology depends on the age of the patient and the frequency of the underlying diseases in a given population. R

ectal bleeding always warrants further assessment and medical advice. It is essential to make appropriate referrals, ie to the right specialist team and with the correct degree of urgency.

Common causes of rectal bleeding

  • Benign anorectal disease:
  • Haemorrhoids
  • Anal fissure
  • Fistula-in-ano
  • Diverticular disease

Inflammatory bowel disease:

  • Crohn’s disease
  • Ulcerative colitis
  • Neoplasia
  • Coagulopathies
  • Arteriovenous malformation

Less common causes of rectal bleeding

Massive upper GI bleeding.
Radiation proctitis.
Ischaemic colitis (mesenteric vascular insufficiency).
Solitary rectal ulcer syndrome.
Dieulafoy’s lesion of small or large bowel.
Meckel’s diverticulum (in adults less often than children).
Rectal varices.
GI tract invasion of non-GI tract malignancy.
Henoch-Schönlein purpura (children).
Trauma (possible sexual abuse).


Important features include:

The quantity and nature of bleeding:

  • Fresh bright red blood usually comes from low down in the GI tract. Examples include fissures and haemorrhoids.
  • Remember bright red blood can also occur with pathology higher in the GI tract (for example, intussusception).
  • Blood mixed in with the stool has usually originated higher in the GI tract.
  • The quantity of blood is very difficult to assess from the history but it is important to get a description from the patient. Indirect measures of the severity of bleeding are essential (see classification, in ‘Presentation’, above).
  • Abnormal weight loss should be identified. Even in infants, failure to thrive may help to identify the likely causes.
  • Change in bowel habit (both frequency of defecation and consistency of stool) must be recognised.[5][6]
  • Tenesmus may be a feature (for example, with fissures).
  • Anal symptoms, for example soreness, itching or prolapse, occur often with piles.
  • Family history of bowel cancer or polyposis must be identified.
  • Past medical history should be carefully documented with particular reference to causes of bleeding and GI tract pathology. Any history of trauma should not be overlooked.
  • Medication history is important, as it may identify causes of bleeding (for example, warfarin and aspirin).


General features. Look for:

  • Pallor or anaemia
  • Cardiovascular signs of shock, including tachycardia and hypotension (including orthostatic hypotension).
  • Cachexia or obvious weight loss.
  • Abdominal examination to identify, for example, masses and hepatomegaly.
  • Stool examination or description:
  • Often possible on a home visit (is the motion still available to be seen?).
  • Blood mixed with stool: the blood is darker and this usually indicates a lesion on the left side of the colon or even transverse colon (often carcinoma or inflammatory bowel disease).
  • Shiny black- or plum-coloured stool is often not recognised by the patient as blood (melaena). This indicates bleeding from higher up the GI tract – these patients need admission for investigation (usually upper GI tract endoscopy), either immediately or through an upper GI tract bleeding fast-track service (see separate article
  • Upper gastrointestinal bleeding (includes Rockall score)).
  • Occult faecal blood loss may be severe enough to cause iron-deficiency anaemia.
  • Bright red blood suggests a lesion in the rectum or anus. If blood is clearly separate from a stool, it indicates an anal lesion, usually haemorrhoids or a fissure – particularly if there are associated anal symptoms (for example, anal pain or pruritus ani) but, occasionally, other pathology (for example, proctitis or anal carcinoma).

This emphasises the need for rectal examination.

  • With blood on the surface of the stool the lesion can be anal, but may be a more proximal lesion (for example, polyp or carcinoma in the rectum or descending colon).

Rectal examination

A digital rectal examination is usually appropriate, both to confirm blood in the rectum and to exclude any rectal or pelvic masses.
Proctoscopy and sigmoidoscopy should identify anorectal sources of bleeding.

When should I call a doctor for blood in the stool (rectal bleeding)?

Any blood in the stool is not normal and should be reported to your health care professional. However, there are certain circumstances that might be considered an emergency and medical care should be accessed immediately. These situations include:

  • Black, tarry stools may be due to bleeding from the esophagus, stomach or duodenum (upper gastrointestinal [GI] tract).

This is especially a potentially serious concern in patients with liver disease and/or portal hypertension who have esophageal varices. This is a potential life threatening situation.

  • Maroon color stool may be caused by an upper GI bleed or a bleeding source in the small intestine.
  • Lightheadedness, weakness, fainting (syncope), chest pain or shortness of breath may be symptoms of significant blood loss.
  • Bleeding that is associated with fever and abdominal pain.

How is the cause of blood in the stool (rectal bleeding) diagnosed?

An accurate diagnosis of the location and the cause of rectal bleeding is important for proper treatment.

Diagnosis with relies on the history and physical examination, anoscopy, flexible sigmoidoscopy, colonoscopy, radionuclide scans, angiograms, and blood tests.

Can rectal bleeding (blood in the stool) be prevented?

Most diseases that cause rectal bleeding are likely preventable, but it is not often possible.

Hemorrhoids can be avoided with proper diet and hydration to prevent constipation and straining to pass stool, but normal pregnancy increases the risk of hemorrhoid formation as does the patient with an acute diarrheal illness.

Avoiding constipation also decreases the risk of diverticulosis, outpouchings in the lining of the colon, and the risk of a diverticular bleed but this may be a consequence of a Western diet.

Alcohol abuse increases the risk of rectal bleeding in a variety of ways, from directly irritating the lining of the GI tract, to decreasing clotting capabilities of blood.

What is the prognosis of rectal bleeding (blood in the stool)?

The prognosis depends upon the underlying diagnosis. Fortunately, the cause of rectal bleeding is often benign, due to hemorrhoids or an anal fissure.

It is important to never ignore blood in the stool or rectal bleeding. It may be a clue to a serious illness and the earlier a diagnosis can be made, the better the chance for a cure.


This will be determined by the likely diagnosis and the severity of bleeding. It can range from dietary advice and suppositories for benign anorectal conditions to colectomy, super-selective embolisation and endoscopic coagulation. It is important to know when to refer.

Source & More Info: and Medicine Net



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