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Rectal Bleeding in Adults

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.

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

Epidemiology[1] Aetiology[1]

It is difficult to obtain 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.

The age of the patient gives a clue to aetiology and as a result forms a part of referral guidelines (see below). Those under the age of 30 presenting with rectal bleeding are more likely to have haemorrhoids, an anal fissure or inflammatory bowel disease. For those over the age of 50, there should be a higher suspicion of colorectal cancer.

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 re-bleeding within a week.

Massive lower GI bleeding requires urgent admission.


Important details to elicit 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.
    • Bright red blood, however, can also occur with pathology higher in the GI tract.
    • 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 obtain a description from the patient. Indirect measures of the severity of bleeding are helpful.
  • Unexplained weight loss.
  • Change in bowel habit (both frequency of defecation and consistency of stool) must be recognised.
  • Tenesmus. May be a feature (for example, with fissures).
  • Anal symptoms - eg, soreness or pain may occur with fissures, itching with piles.
  • Family history of bowel cancer or polyposis.
  • Past medical history. Careful documentation with particular reference to causes of bleeding and GI tract pathology. Any history of trauma should not be overlooked.
  • Medication history. This may identify causes of bleeding (for example, warfarin and aspirin).



The investigations chosen will depend on the particular mode of presentation and likely diagnosis. Unnecessary investigation should not delay referral where there is a high suspicion of malignancy. Rectal examination and FBC are worth performing on most patients prior to referral. Further blood tests will be guided by the presentation.

Blood tests

There is no evidence that tumour markers such as carcinoembryonic antigen (CEA) are useful as diagnostic tools in this situation.[1]

Further investigation in secondary care[1, 4]

Barium enema is no longer considered to have a role in the investigation of rectal bleeding, due to its poor sensitivity and tolerability.

Guidance on urgency of referral for one of these investigations is given below.


This will be determined by the eventual diagnosis and the severity of bleeding. It is important to know when to refer.

When to refer

Referral may be:

  • Routine - may be appropriate for low-risk and benign conditions.
  • Urgent (within two weeks).
  • Emergency (immediate) when there is massive bleeding.

Referral of suspected cancer[8]

Refer the following people under a two week wait suspected cancer pathway for colorectal cancer:

  • Those aged ≥40 with unexplained weight loss and abdominal pain.
  • Those aged ≥50 with unexplained rectal bleeding.
  • Those aged ≥60 with:
    • Iron-deficiency anaemia.
    • Or, change in bowel habit.
  • Those whose tests have been positive for occult blood in their faeces - NICE guidelines advise occult blood is tested for in:
    • Those aged ≥50 with unexplained abdominal pain or weight loss.
    • Those aged <60 with change in bowel habit or iron-deficiency anaemia.
    • Those aged ≥60 with anaemia, whether iron-deficient picture or not.

Consider referring the following people under a two week wait suspected cancer pathway for colorectal cancer:

  • All those with a rectal or abdominal mass.
  • Those aged <50 with rectal bleeding along with any of the following:
    • Unexplained abdominal pain.
    • Unexplained change in bowel habit.
    • Unexplained weight loss.
    • Unexplained iron-deficiency anaemia.

Consider referring any person with an unexplained anal mass or unexplained anal ulceration under a two week wait suspected cancer pathway for anal cancer.

Assessing acute bleeding[9]

The Scottish Intercollegiate Guidelines Network (SIGN) has produced guidance for those assessing cases of rectal bleeding in hospital. This may also be useful for those considering referral.

Prognosis[10, 11]

This naturally depends on the cause, as well as other factors such as age and comorbidity.

No individual feature or symptom associated with rectal bleeding is strongly predictive of the eventual cause being diagnosed as colorectal cancer. However, certain associated features do make this cause more likely. These include:

Further reading & references
  1. Rectal bleeding: commissioning guide; Royal College of Surgeons - NICE accredited, 2013
  2. van Rheenen PF, Van de Vijver E, Fidler V; Faecal calprotectin for screening of patients with suspected inflammatory bowel disease: diagnostic meta-analysis. BMJ. 2010 Jul 15;341:c3369. doi: 10.1136/bmj.c3369.
  3. Guidelines for the management of inflammatory bowel disease in adults; British Society of Gastroenterology (2011)
  4. Burling D, East JE, Taylor SA; Investigating rectal bleeding. BMJ. 2007 Dec 15;335(7632):1260-2.
  5. Colorectal cancer: The diagnosis and management of colorectal cancer; NICE Clinical Guideline (November 2011)
  6. Computed tomographic colonography (virtual colonoscopy); NICE Interventional Procedure Guidance, June 2005
  7. Guideline on the use of CT colonography for suspected colorectal cancer; British Society of Gastrointestinal and Abdominal Radiology (BSGAR) and the Royal College of Radiologists, 2014
  8. Suspected cancer: recognition and referral; NICE Clinical Guideline (2015)
  9. Management of acute upper and lower gastrointestinal bleeding; Scottish Intercollegiate Guidelines Network - SIGN (September 2008)
  10. Astin M, Griffin T, Neal RD, et al; The diagnostic value of symptoms for colorectal cancer in primary care: a systematic review. Br J Gen Pract. 2011 May;61(586):e231-43. doi: 10.3399/bjgp11X572427.
  11. Olde Bekkink M, McCowan C, Falk GA, et al; Diagnostic accuracy systematic review of rectal bleeding in combination with other symptoms, signs and tests in relation to colorectal cancer. Br J Cancer. 2010 Jan 5;102(1):48-58. doi: 10.1038/sj.bjc.6605426. Epub 2009 Nov 24.
Original Author: Dr Richard Draper Current Version: Dr Mary Harding Peer Reviewer: Dr John Cox
Last Checked: 01/07/2015 Document ID: 2703  Version: 25 © EMIS


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