Rectal bleeding in adults

What is rectal bleeding?

Rectal bleeding, or haematochezia, describes the passage of fresh blood through the anus. The blood may be bright red or dark red. It may be mixed in with stools, or separate.

Rectal bleeding usually originates from the GI tract below the ligament of Treitz, ie anywhere from the duodenojejunal flexure to the anus. It can also, rarely, be caused by a massive upper GI bleed.¹

Rectal bleeding should be differentiated from melaena. Melaena describes the passage of digested or partially-digested blood per rectum, which appears as black, tarry stools with a characteristic foul odour. Melaena occurs due to upper gastrointestinal bleeding, ie bleeding originating above the ligament of Treitz.

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

Epidemiology²

• Rectal bleeding is a very common symptom. It occurs in adults of all ages.

• The 1-year prevalence in adults is about 10% in the UK. Most of this will not be reported.

• The majority of cases of rectal bleeding are due to benign causes, particularly haemorrhoids and anal fissures. However, there are many other possible causes, some of which are sinister. In particular the cause to be excluded is colorectal cancer.

Causes of rectal bleeding (aetiology)^{3 4}

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. However, nearly one third of rectal cancer patients are younger than 55 years of age, and the incidence of colorectal cancer in young adults has steadily increased over the past few decades.⁵

Common causes of rectal bleeding

• Benign anorectal disease:
  

  • Haemorrhoids.

  • Anal fissure.

  • Fistula-in-ano.

• Diverticular disease.

• Inflammatory bowel disease:
  

  • Crohn's disease.

  • Ulcerative colitis.

• Colonic polyps.

• Colorectal or anal cancer.

Less common causes of rectal bleeding

• Infectious gastroenteritis.

• Coagulopathies.

• Arteriovenous malformation (angiodysplasia).

• Massive upper gastrointestinal (GI) bleeding.

• Radiation proctitis.

• Ischaemic colitis (mesenteric vascular insufficiency).

• Solitary rectal ulcer.

• 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.

• Trauma (possible sexual abuse).

• Sexually transmitted infections.

Symptoms of rectal bleeding (presentation)

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. The severity of rectal bleeding can be categorised as follows:

• Occult bleeding - presenting with anaemia or a positive faecal test for blood or blood products, but no visible rectal bleeding.

• Moderate bleeding - presenting with rectal bleeding (fresh or dark), 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 emergency admission and resuscitation.

Symptoms

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.

• 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, direct-acting oral anticoagulants and aspirin).

Examination

• 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. Look for:

  • Masses.

  • Hepatomegaly.

• Stool examination or description:
  

  • Examination of stool may be possible, particularly on a home visit if the motion is 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 the separate Upper Gastrointestinal bleeding (includes Rockall Score) article).

  • 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, to confirm blood in the rectum, to exclude any rectal or pelvic masses, and to visualise or palpate any anorectal sources of the bleeding.

  • If the patient is not to be referred to secondary care for investigation, a digital rectal examination is essential.

  • Remember the finding of haemorrhoids or fissures does not necessarily exclude more proximal causes of bleeding.

  • If there is already a clear reason to refer the patient for further investigation on a two-week-wait pathway, a digital rectal examination is optional (depending on local referral guidelines), but helpful. It may assist secondary care triage (eg, by identifying an anal cancer). If a digital rectal examination is not done prior to referral, it should be done prior to endoscopy, as low rectal lesions can otherwise be missed.⁶

  • Proctoscopy should help identify anorectal sources of bleeding. It cannot be used as a substitute for sigmoidoscopy, however, in ruling out serious pathology.³

Diagnosing rectal bleeding (investigations)

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. Quantitative faecal immunohistochemistry testing (qFIT) is an important investigation in patients where colorectal cancer is a possibility (a negative result makes colorectal cancer unlikely, even in the presence of visible rectal bleeding),⁷and is usually a prerequisite for lower GI 2-week-wait referrals, to aid triage.⁸

Further blood tests will be guided by the presentation.

Blood tests

• FBC (and group and save if bleeding is profound or anaemia suspected).

• Ferritin and iron studies if iron-deficiency anaemia is suspected.

• Clotting studies may be appropriate, if a bleeding diasthesis is suspected.

• LFTs may be indicated if liver disease is suspected.

Stool tests

• Quantitative faecal immunochemical testing (qFIT) is a valuable investigation in people with symptoms of colorectal cancer, including visible rectal bleeding.⁷

  • Whilst it is somewhat counter-intuitive, faecal haemoglobin (the substance that qFIT measures) is often undetectable even in patients with visible rectal bleeding.⁹

  • At a threshold of 10 µg of haemoglobin per gram of faeces, qFIT has a 96.6% sensitivity and 71.7% specificity for colorectal cancer in the presence of visible rectal bleeding. ¹⁰ A negative qFIT is therefore reassuring, whereas a positive qFIT should trigger urgent referral for lower GI investigations.

  • qFIT may also improve the detection of other serious colonic pathologies, such as high-risk polyps and inflammatory bowel disease.¹¹

  • The underlying reasons why qFIT is still a useful discriminator for serious bowel disease in the presence of visible rectal bleeding are not fully clear. It is possible that anorectal bleeding sources (such as haemorrhoids) cause the surface of stool to be coated in blood, but not the centre of the stool, from which the qFIT sample is mostly taken.⁹ Another explanation is that qFIT detects haemoglobin from lysed red blood cells, and not intact red blood cells - fresh bleeding from benign anorectal sources may be more likely to produce the latter.

• Faecal calprotectin is a useful screen in younger patients suspected of having inflammatory bowel disease, and has a high positive predictive value.¹²

There is no evidence that tumour markers such as carcinoembryonic antigen (CEA) are useful as diagnostic tools in this situation.³

Further investigation in secondary care¹³

• Flexible sigmoidoscopy. This is the investigation of choice for younger patients where there is concern about pathology other than haemorrhoids, or those who have persistent bleeding following treatment for haemorrhoids. It may also be useful as an alternative to colonoscopy in people with persistent or recurrent rectal bleeding and a negative qFIT - there is some limited evidence that qFIT-negative colorectal cancers are likely to be detectable on flexible sigmoidoscopy, without the need for a full colonoscopy.⁷

• Colonoscopy. This is the definitive investigation where there is a high suspicion of malignancy, or a family history. It allows tissue biopsy and removal. However, it is an unpleasant test.

• Virtual colonoscopy (computerised tomography (CT) colonography). This method uses 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. It is approved by National Institute for Health and Care Excellence (NICE) and Royal College of Radiologists (RCR) guidelines as a highly sensitive and well-tolerated tool in the diagnosis of colorectal cancer.¹⁴

Colonoscopy and CT colonography appear to perform equally well for the detection of colorectal cancer. Colonoscopy is generally still considered the standard method of investigation, as it allows biopsies to be taken, endoscopic polypectomy to be performed, and non-neoplastic pathology to be better-investigated. CT colonography tends to be used in older or frailer people, or when colonoscopy is incomplete or contraindicated.⁷

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

Management

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 (outside the two-week-wait pathway); eg, for suspected inflammatory bowel disease.

• Urgent suspected cancer (the two-week-wait pathway).

• Emergency (immediate) when there is massive bleeding.

Referral of suspected cancer¹⁵

In recent years, qFIT testing has become widespread in primary care to guide the decision around who to refer for further investigation to rule out colorectal cancer. NICE recommends performing qFIT testing in people:

• Aged over 50 with any of the following unexplained symptoms:

  • Rectal bleeding.

  • Abdominal pain.

  • Weight loss.

• Aged under 50 with rectal bleeding, and either of the following unexplained symptoms:

  • Abdominal pain.

  • Weight loss.

• With an abdominal mass.

• With a change in bowel habit.

• With iron-deficiency anaemia.

• Aged 40 or over with unexplained weight loss.

• Aged 60 and over with anaemia, even in the absence of iron deficiency.

An urgent suspected colorectal cancer referral should be made if the qFIT test is positive (>10μg of haemoglobin per gram of faeces).

People with a negative qFIT result should still be referred urgently if the clinical picture is still strongly suggestive of cancer (eg, there is an unexplained abdominal mass).

Likewise, people with a palpable rectal mass, or an unexplained anal mass or ulcer, should be referred urgently, regardless of the qFIT result (which does not need to be performed in these patients).

Outside of these situations, though, a negative qFIT makes colorectal cancer very unlikely⁷⁸ and it is reasonable to provide reassurance and manage these patients in primary care, at least initially, assuming there are no other signs or symptoms of serious pathology.

Patients with a negative qFIT result should be given safety-netting and advised to return if the symptoms of rectal bleeding do not settle, or if they develop other symptoms of concern. Persistent, recurrent, or unexplained rectal bleeding should prompt referral, even with a negative qFIT.⁷

Assessing acute bleeding¹⁶

The British Society of Gastroenterology has produced guidance for those assessing cases of acute lower intestinal bleeding in hospital. This may also be useful for those considering referral.

• Patients presenting with lower gastrointestinal bleeding (LGIB) should be stratified as unstable or stable (unstable defined as a shock index >1, the shock index being the ratio between heart rate and systolic blood pressure). Stable bleeds should then be categorised as major or minor, using a risk assessment tool such as the Oakland score (a calculation based on various criteria such as age, haemoglobin level and digital rectal examination findings).

• Patients presenting with a minor self-terminating bleed (such as those with an Oakland score ≤8 points), with no other indications for hospital admission may be discharged for urgent outpatient investigation.

• Patients with a major bleed should be admitted to hospital for colonoscopy on the next available list.

• If a patient is haemodynamically unstable or has a shock index of >1 after initial resuscitation and/or active bleeding is suspected, CT angiography (CTA) should be considered, followed by endoscopic or radiological therapy.

• As LGIB associated with haemodynamic instability may be indicative of an upper gastrointestinal bleeding source, an upper endoscopy should be performed immediately if no source is identified by initial CTA. If the patient stabilises after initial resuscitation, gastroscopy may be the first investigation.

• Where indicated, catheter angiography with a view to embolisation should be performed as soon as possible after a positive CTA to maximise chances of success. In centres with a 24/7 interventional radiology service, this should be available within 60 minutes for haemodynamically unstable patients.

• No patient should proceed to emergency laparotomy unless every effort has been made to localise bleeding by radiological and/or endoscopic modalities, except under exceptional circumstances.

• Red blood cell transfusion may be required.

• If the patient is on antiplatelet/anticoagulant therapy, this may need to be adjusted.

Prognosis¹⁷

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:

• Weight loss.

• Age over 50.

• Change in bowel habit.

• Iron-deficiency anaemia.

• Blood mixed with stool.

• A strong family history of colorectal cancer.³