Red flag symptoms: Rectal bleeding

It is important to rule out the possibility of colorectal/anal malignancy and inflammatory bowel disease.

Rectal bleeding often represents a benign condition, such as anal fissure (SPL)
Rectal bleeding often represents a benign condition, such as anal fissure (SPL)

Red flags:

  • Weight loss
  • Change in bowel habit, especially diarrhoea and/or increased frequency
  • Iron-deficiency anaemia
  • Abdominal mass
  • Rectal mass

Rectal bleeding is a common symptom in adults presenting to primary care. In most cases, it is benign, intermittent and self-limiting.

Rectal bleeding often represents a benign anal condition, such as piles or an anal fissure. However, it is important to rule out colorectal/anal malignancy and inflammatory bowel disease as potential causes. Other possible causes of rectal bleeding include angiodysplasia, diverticular disease and colonic polyps.

The patient's age is particularly relevant because younger patients are more likely to have an anal fissure, piles or inflammatory bowel disease as a cause for rectal bleeding.

This is in contrast to patients over the age of 50 years, for whom rectal bleeding is more likely to represent a malignant cause.1

Possible causes of rectal bleeding
  • Colorectal malignancy
  • Anal malignancy
  • Inflammatory bowel disease
  • Ischaemic colitis
  • Diverticular disease
  • Colonic polyps
  • Angiodysplasia

Clinical assessment

In patients presenting with rectal bleeding, it is helpful to assess the volume and frequency of blood loss.

It is difficult to assess the volume of blood and it may be useful to ask whether the patient has noticed blood streaks, teaspoons of blood or the passage of clots.

Melaena usually indicates bleeding from the upper GI tract, but bleeding from the right side of the colon may also cause it.1

Haematochezia refers to the passage of gross blood per rectum. It is usually indicative of bleeding from the lower GI tract, but may also indicate significant bleeding from the upper GI tract. Patients presenting with frank blood loss should be assessed for signs of shock and managed as a medical emergency.

It is helpful to establish whether the patient has noticed blood mixed in with the stool or on the surface of the stool and whether there has been any passage of mucus.

A travel history may be relevant. Further history includes asking about previous episodes, the presence of abdominal pain, changes in bowel habit - especially loose stools with or without an increase in frequency - symptoms of anaemia, jaundice and weight loss.

It is important in the history to identify patients who may be at increased risk of colorectal malignancy, for example, those with a history of ulcerative colitis and/or with a relevant family history in a first- degree relative.

Bleeding is more likely to be severe if there is evidence of chronic liver disease or coagulopathy, or if the patient is on anticoagulant therapy.

Physical examination should include a general examination with measurement of vital signs and an assessment of lymphadenopathy. Abdominal examination should include digital rectal examination.

Detecting an unexplained iron- deficiency anaemia may necessitate urgent referral. Blood tests in primary care are helpful in patients presenting with equivocal symptoms to help guide further management.

In younger patients where there is clinical suspicion of inflammatory bowel disease, a faecal calprotectin test may be helpful.


If there is clinical suspicion of colorectal or anal malignancy, the patient should be referred via the two-week wait pathway, if appropriate.

Urgent referral is recommended for patients aged 40 and over who present with rectal bleeding with a change of bowel habit with looser stools and/or increased stool frequency that has been present for six weeks or more.2

If the bleeding has persisted for six weeks or more without anal symptoms and/or without a change in bowel habit in patients aged 60 and over, urgent referral is indicated.2 Moreover, in patients aged 60 and over, those presenting with a change in bowel habit with looser and/or more frequent stools for more than six weeks should be referred urgently to secondary care, regardless of the presence of rectal bleeding.2

NICE guidance also advises that patients presenting with a right lower abdominal mass or a palpable rectal mass should be referred urgently.2 Furthermore, if men have an unexplained iron-deficiency anaemia with Hb 11g/100mL or below, and if non-menstruating women have an unexplained iron-deficiency anaemia with Hb 10g/100mL or below, urgent referral is advisable.2

Colonoscopy is the first choice investigation in rectal bleeding because it allows tissue sampling. In some patients, virtual colonoscopy may be more appropriate because it is minimally invasive.

Click here to take a test on this article and claim a certificate on MIMS Learning


1. 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; 102: 48-58.
2. NICE. Referral guidelines for suspected cancer. Quick reference guide. CG27. London, NICE, June 2005.

Have you registered with us yet?

Register now to enjoy more articles and free email bulletins


Already registered?

Sign in