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Rectal Bleeding in Adults

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.

  • 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


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:


Differential diagnosis

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:


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.


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.


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, June 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 (UK access only)
  15. Management of acute upper and lower gastrointestinal bleeding; Scottish Intercollegiate Guidelines Network - SIGN (September 2008)
Original Author: Dr Richard Draper Current Version: Dr Hayley Willacy Peer Reviewer: Dr John Cox
Last Checked: 13/06/2012 Document ID: 2703  Version: 23 © EMIS


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