Red flag symptoms
- Weight loss
- Change in bowel habit, especially diarrhoea and/or increased frequency
- Iron-deficiency anaemia
- Abdominal mass
- Rectal/anal mass
- Faecal occult blood
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|
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 with unexplained weight loss and abdominal pain
- aged 50 and over with unexplained rectal bleeding
- aged 60 and over with iron deficiency anaemia OR change in bowel habit OR tests showing occult blood in their faeces
NICE guidance also advises that patients presenting with an abdominal mass or a palpable rectal mass should be referred urgently.2 An urgent referral is also warranted for an unexplained anal mass or unexplained anal ulceration. The latter is a new addition to the suspected cancer guideline.2
Furthermore, urgent referral for colorectal cancer should be considered in adults under the age of 50 with rectal bleeding and any of the following symptoms: abdominal pain, change in bowel habit, weight loss and iron-deficiency anaemia.
Faecal immunochemical (FIT) testing, a type of faecal occult blood test, detects small amounts of blood in stool samples using antibodies specific to human haemoglobin. This is an alternative to guaiac-based faecal occult blood tests, which are less specific. FIT testing can be used in primary care to assess people who are at a low risk of colorectal cancer, and help determine whether they should be referred for further investigations where they do not meet the criteria for a suspected cancer pathway referral as recommended by NICE.3
NICE's guideline on suspected cancer previously recommended that faecal occult blood tests should be offered to adults without rectal bleeding who are aged 50 or over with unexplained abdominal pain or weight loss, OR are aged under 60 with changes in their bowel habit or iron-deficiency anaemia, OR are aged 60 or over and have anaemia without iron deficiency.2
Colonoscopy is the first choice investigation in rectal bleeding because it allows for the whole colon to be visualised and for biopsies to be taken. In some patients, CT colonography or virtual colonoscopy may be more appropriate.
- Dr Kochhar is a GP in Bexhill, East Sussex
This is an updated version of an article that was first published in January 2015.
- 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.
- NICE. Suspected cancer: recognition and referral. NG12. June 2015 [updated July 2017].
- NICE. Quantitative faecal immunochemical tests to guide referral for colorectal cancer in primary care. DG30. July 2017.