Rectal Bleeding in Adults

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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

For details on rectal bleeding in children see separate article Rectal bleeding in children.

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. Rectal 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.

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  • The incidence of rectal bleeding is essentially unknown.
  • Empirically it is a very common symptom, particularly in general practice. Few patients with rectal bleeding require hospital admission.
  • The incidence rises with age (about 200 times between the third and ninth decades of life), as does the likelihood of hospital admission for lower gastrointestinal (GI) haemorrhage.
  • In Western societies diverticulosis is common and hence it is a common cause of rectal bleeding.

It is difficult to get accurate figures for the relative frequency of the different causes of rectal bleeding. Studies have differing results according to population demographics, patient selection, size of study and other confounding factors. However, it is essential to understand the aetiology, as this shapes the investigations, management and ultimately the likely outcome.

It is also important to remember rare causes. Occasionally, bright red blood appears rectally from massive haemorrhage high up in the GI tract. In as many as 20% of patients no cause can be identified even when there has been considerable blood loss.

Common causes of rectal bleeding

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.
  • Endometriosis.
  • 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).

In assessing rectal bleeding it is important to identify important presenting features as these can give clues to the likely aetiology and severity of bleeding. It is, for example, important to assess the amount of bleeding. There are three classifications according to the amount of bleeding:

  • Occult bleeding - presenting with anaemia.
  • Moderate bleeding - presenting with rectal bleeding (fresh or dark), or melaena in a patient who is haemodynamically stable.
  • Massive bleeding - presenting with large amounts of blood passed rectally (may be dark but often fresh).
    There may be:
    • Shock with systolic blood pressure below systolic 90 mm Hg.
    • Initial drop in haematocrit and haemoglobin less than 6 g/dL.
    • Requirement for transfusion of two units of blood or more.
    • Persistence of bleeding for more than three days.
    • Significant rebleeding within a week.

Massive lower GI bleeding requires urgent admission.


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.[3]
    • 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.

Patients with rectal bleeding can have bled from anywhere in the GI tract and there are many possible causes. The likely causes can be appreciated from the aetiology and are different in different age groups and different populations.

The different underlying diseases can cause different clinical features. For example:

  • Benign anorectal disease:
    • Usually causes intermittent rectal bleeding.
    • Does not exclude more proximal causes of bleeding.
    • Rarely causes massive rectal bleeding but can do so with, for example, portal hypertension.
  • Diverticulitis:
    • Is very common in the over-60s, being present in about half of patients. About 20% of such patients develop rectal bleeding.
    • Is most common in the sigmoid and descending colon and can therefore cause bright red rectal bleeding.
    • Causes bleeding which will stop spontaneously in 20% of patients. In 5% of cases the bleeding is massive.
  • Colonic angiodysplasias:
    • Generally cause slow but repeated episodes of bleeding.
    • Are acquired lesions and more common in the over-60s.
    • The bleeding is often occult and sited on the right side of the colon and caecum.
    • Can present with iron deficiency anaemia.
  • Inflammatory bowel disease:
    • Rarely causes massive GI bleeding.
    • Usually causes bloody diarrhoea when the cause is ulcerative colitis.[7]
    • Lower GI bleeding is less common with Crohn's disease compared with ulcerative colitis.[8]
  • Adenocarcinoma of the colon and rectum:
    • These are common cancers.
    • Bleeding is usually occult and patients usually present with other signs and symptoms (for example, change of bowel habit or anaemia).
    • Is more common in older patients.

The investigations chosen will depend on the particular mode of presentation and likely diagnosis. It is important that unnecessary investigation should not delay referral. Rectal examination and FBC are worth performing on all patients prior to referral.

  • Digital rectal examination, proctoscopy and sigmoidoscopy may be performed as part of the initial examination.[9][10]
  • Blood tests may be required:
    • FBC (and group and save if bleeding is profound or anaemia suspected).
    • Clotting studies may be appropriate.
    • Ferritin and iron studies if iron deficiency anaemia is suspected.
    • LFTs may be indicated if liver disease is suspected.
  • Refer for sigmoidoscopy or colonoscopy where appropriate.[10] Virtual colonoscopy may be an option.[11] (This method uses computed tomography (CT) to examine the prepared, distended colon. Interpretation of the data combines two dimensional methods with three-dimensional 'endoscopic fly-through' simulations, hence "virtual" colonoscopy.[12] The procedure does not require sedation, is well tolerated by patients and is relatively safe.)

    Guidance on urgency of referral is given below. Rapid access referral may be appropriate, and the patient may need immediate admission if bleeding is severe. Further investigations to identify the source of bleeding include:
    • Selective mesenteric angiography, which is particularly useful at identifying the point of bleeding. For rectal bleeding this is usually the inferior mesenteric artery (rather than superior mesenteric artery or coeliac axis).
    • Nuclear scintigraphic imaging (ten times more sensitive than mesenteric angiography).
    • CT scanning (helical used when routine work-up fails to detect cause of bleeding).
    • Double-contrast barium enema may be useful but should be avoided with acute bleeding, as it may make subsequent examination difficult.

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.

When to refer

Referral may be urgent (within two weeks) to make a diagnosis or as an emergency (immediate) when there is massive bleeding. Routine referral may be appropriate for low-risk and benign conditions.

Referral of suspected cancer

Guidance for referral of suspected lower GI tract cancers:
  • Refer patients urgently (to be seen within two weeks) who have had either:[13][14]
    • Rectal bleeding plus change of bowel habit (increased frequency or change to looser motions) persisting for six weeks and are aged 40 years or older.
    • Palpable rectal or right-sided lower abdominal mass.
    • Iron-deficiency anaemia without any obvious cause (<11 g/dL in men and <10 g/dL in postmenopausal women).
  • Refer patients aged over 60 urgently (to be seen within two weeks) when there is:
    • Rectal bleeding without anal symptoms (anal discomfort, soreness, pruritus ani or local mass) persisting for six weeks.
    • Change in bowel habit (increased frequency or change to looser motions) persisting for six weeks without rectal bleeding.

Patients who have a change in bowel habit with constipation or infrequent bowel action or abdominal pain without evidence of obstruction have a very low likelihood of bowel cancer. However, such patients usually need standard outpatient referral for investigation.

Assessing the bleeding

Guidance for those assessing cases of rectal bleeding in hospital has also been produced.[15] This is useful also for those considering referral.

  • Follow-up in outpatients is suggested to be appropriate when:
    • The patient is less than age 60.
    • There is no haemodynamic disturbance.
    • There is no other evidence of massive rectal bleeding.
    • An obvious source of bleeding has been identified by rectal examination and/or sigmoidoscopy.
  • Immediate admission is considered appropriate when:[15]
    • The patient is over the age of 60.
    • There is haemodynamic disturbance.
    • There is evidence of massive bleeding.
    • Aspirin, non-steroidal anti-inflammatory drugs (NSAIDS) or other drugs likely to exacerbate bleeding are being taken.
    • There is significant comorbidity.

The likelihood of complications depends on the cause of rectal bleeding and the severity of bleeding. Generally speaking, cases are more likely to produce complications, morbidity and mortality when:

  • There is massive haemorrhage.
  • Surgery is required.
  • Invasive investigations are required.
  • Hospital admission is necessary.
  • The underlying disease is associated with complications (cancer, inflammatory bowel disease).
  • In the very young and the old.

This also depends on many factors. Mortality rate may be as high as 21% in cases of massive haemorrhage in over 65 year-olds.

Preventive measures should be aimed at the underlying diseases and better management of both the complications and more severe cases of haemorrhage. Earlier diagnosis and treatment of GI tract carcinoma would prevent some cases of haemorrhage but, often, it is the bleeding which triggers the diagnostic process. It may be that screening for early occult bleeding will reduce cases of more advanced carcinoma with anaemia and more severe bleeding.

Further reading & references

  1. Haemorrhoids, Prodigy (May 2008)
  2. Anal fissure, Prodigy (May 2008)
  3. Diverticular disease and diverticulitis, Prodigy (March 2008)
  4. Guidelines for the management of inflammatory bowel disease in adults; British Society of Gastroenterology (2011)
  5. Diarrhoea - adults assessment; NICE CKS, December 2010
  6. Constipation, Prodigy (January 2008)
  7. Ulcerative Colitis; NICE CKS, June 2010
  8. Crohn's Disease, Prodigy (June 2010)
  9. Rectal cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up; European Society for Medical Oncology (2010)
  10. Primary colon cancer: ESMO Clinical Practice Guidelines for diagnosis, adjuvant treatment and follow-up; European Society for Medical Oncology (2010)
  11. Computed tomographic colonography (virtual colonoscopy), NICE Interventional Procedure Guideline (2005)
  12. Burling D, East JE, Taylor SA; Investigating rectal bleeding. BMJ. 2007 Dec 15;335(7632):1260-2.
  13. Referral for suspected cancer; NICE Clinical Guideline (2005)
  14. GI (lower) cancer - suspected; NICE CKS, July 2005
  15. Management of acute upper and lower gastrointestinal bleeding; Scottish Intercollegiate Guidelines Network - SIGN (September 2008)

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Richard Draper
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
2703 (v23)
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