Rectal Bleeding


rectal bleeding image
Image courtesy of Cary Gastro Opens in new window

Rectal bleeding or haematochezia is the passage of bright red, bloody stools from the rectum, and is to be distinguished from melaena, which is stool with blood that has been altered by the gut flora and appears black and ‘tarry’. Commonly associated with lower gastrointestinal bleeding Opens in new window, rectal bleeding affects 20% of western society at some stage in their lives.

Patients may present with minor self-limiting episodes, evidence of occult blood loss with anaemia, or more severe bleeding with haemodynamic instability. Acute lower gastrointestinal haemorrhage accounts for approximately 20% of all cases of gastrointestinal haemorrhage.

Rectal blood loss usually originates distal to the ligament of Treitz (the duodenal suspensory ligament at the junction of the duodenum and the jejunum) in the distal duodenum. However, in a small group of cases the cause may be more proximal — in the duodenum, stomach or distal oesophagus.

Appropriate investigation and management is dictated by the severity of blood loss. Those with minor bleeds can often be investigated and managed as outpatients. Moderate bleeding may require inpatient investigation. Severe or continuous bleeding or significant re-bleeding within 1 week warrants in-hospital management. Massive lower gastrointestinal haemorrhage is characterized by haemodynamic instability and transfusion of at least two units of packed red blood cells.

Mortality from acute lower gastrointestinal bleeding is approximately 5–10%, and the risk increases with age (particularly in those over 60), concomitant medical problems, difficulty in locating a bleeding source, transfusion requirement of more than 5 units of blood, and surgery in the unstable patient.

1.    Aetiology

The aetiology of rectal bleeding varies with age. In patients under 50 years, haemorrhoids Opens in new window are by far the most common cause, followed by anal fissures, benign polyps and inflammatory bowel disease. Diverticulosis and angiodysplasia are the most common causes in patients aged over 50, followed by carcinoma, polyps, colitis and rare malignancies such as anorectal melanoma. In this age group, the risk of colonic neoplasms increases with every year of age.

1.1.    Diverticulosis

Colonic diverticula are acquired defects in the bowel wall occurring at the point of entry of nutrient vessels. They are present in more than 50% of people over 60 years of age, and the incidence increases with age. Diverticula are common in the distal colon and are the source of lower gastrointestinal bleeding in up to 60% of cases in adults. The bleeding is arterial and usually from a single diverticulum. It is acute, painless, and can be alarming in its volume. However, in most patients the blood loss stops spontaneously.

1.2.    Angiodysplasia

Angiodysplastic lesions are acquired submucosal vascular ectasia and account for up to 12% of cases of lower gastrointestinal bleeding in adults. Rare vascular anomalies include arteriovenous malformation, haemangioma, and syndromes such as hereditary haemorrhagic telangiectasia. Blood loss is usually chronic, although a minority can present with acute haemorrhage. Although most cases tend to resolve spontaneously, they often re-bleed.

1.3.    Neoplasia

Neoplasms of the bowel present as painless bleeding and may have associate symptoms of weight loss, altered bowel habit, abdominal pain or intestinal obstruction.

1.4.    Inflammatory Bowel Disease (See here Opens in new window)

Small to moderate amounts of bright blood mixed in with the stool occur in patients with ulcerative colitis and Crohn’s disease. These patients are usually young (25–30 years) with widespread disease.

1.5.    Colitis

Colitis can be due to parasitic and bacterial infections, ischaemic bowel and post-radiation therapy. Haemorrhagic radiation proctitis is a potential complication of prostate brachytherapy.

1.6.    Anorectal Disorders

Haemorrhoids Opens in new window are the most common cause of rectal bleeding, usually causing intermittent painless bleeding associated with defecation. Rectal varices may occur in association with portal hypertension. It is prudent to remember that benign anorectal disease on examination does not exclude the possibility of a more proximal source of bleeding or pathology.

1.7.    Aortoenteric Fistula

This complication occurs as a rare sequela of endovascular abdominal aortic aneurysm repairs and is probably due to inflammation and prosthetic leak. There may be a ‘herald bleed’ prior to catastrophic exsanguinating haemorrhage. High levels of suspicion should be maintained for all patients with gastrointestinal bleeding and previous abdominal aortic aneurysm repair.

1.8.    Miscellaneous

Rectal ulcers may result from local trauma due to insertion of foreign bodies and aberrant sexual practices. Non-steroidal anti-inflammatory drugs (NSAIDs), inherited or acquired bleeding disorders, and rarely, infection in association with HIV, need to be considered.

2.    History

Patients’ estimates of blood loss are unreliable. However, the number and frequency of bowel movements, their color and composition (e.g. mixed with stool, presence of clots), associated symptoms (e.g. abdominal pain, weight loss) and symptoms of volume depletion (syncope Opens in new window, dizziness, dyspnoea) are helpful. The diagnosis of neoplasia may be suggested by a history of altered bowel habit or abdominal pain, and constitutional symptoms such as weight loss and lethargy. Pain is unusual with bleeding from diverticular disease or angiodysplasia.

A history of haematemesis is useful in directing initial investigations to the upper tract. Enquiry should include past medical history (especially of cardiorespiratory disease), antithrombotic and antiplatelet therapy, NSAID use and alcohol intake.

3.    Examination

Initial evaluation should focus on the assessment of haemodynamic stability. Respiratory rate is an important early indicator of shock. Orthostatic hypotension indicates a significant blood volume loss, although it can also be caused by drugs and autonomic dysfunction. Examination should look for abdominal signs, evidence of chronic liver disease and coagulopathy. Digital rectal examination is essential to confirm rectal bleeding and detect local pathology.

4.    Investigations

4.1.    Blood Tests

A full blood examination (principally for anaemia) and serum electrolyte analysis (for renal function) is indicated in all but the young patient with mild bleeding and obvious anorectal disease. Other tests will be guided by the clinical presentation.

4.2.    Endoscopy

Proctoscopy is particularly useful for the diagnosis of anorectal disease, offering the highest detection rate for haemorrhoids and anal fissures. Rigid or flexible sigmoidoscopy enables inspection of the mucosa of the rectum, sigmoid colon and distal descending colon. Colonoscopy offers the added ability to establish tissue diagnosis by biopsy and perform therapeutic interventions. It is the investigation of choice in the stable patient with adequate bowel preparation.

4.3.    Imaging

4.3.1    Angiography

Selective mesenteric angiography has for many years been the investigation of choice for localization of bleeding, by injection of contrast into the superior mesenteric artery, inferior mesenteric artery and celiac trunk, in sequential order. Sensitivity varies widely, but it is reported to detect bleeding at a rate of more than 0.5 mL/min. Angiography also offers a therapeutic option, through either selective vasooressin infusion or embolization. Unlike colonoscopy and scintigraphy, angiography does not require any special preparation.

4.3.2.    CT

CT colonography, also known as virtual colonoscopy, is a relatively new technique that is becoming increasingly popular. This three dimensional CT imaging is a sensitive diagnostic tool for the detection of colorectal polyps in cases with adequate bowel preparation.

Magnetic resonance imaging (MRI) is another useful modality for rectal cancer and provides good visualization of important local prognostic factors. Endoscopic ultrasound is the modality of choice for small, superficial tumors. Given its current promise of offering high sensitivity, specificity and accuracy, the indications for positron emission tomography (PET) may well expand in the future, but its final role is yet to be confirmed.

4.3.3.    Double-Contrast Barium Enema

Barium studies have no place in the acute setting, largely because of practical difficulties and an inadequately prepared bowel. In addition, it hampers subsequent diagnostic investigations, including angiography and colonoscopy. It lacks sensitivity in detecting smaller dysplastic lesions and cannot provide a tissue diagnosis. Barium studies may complement colonoscopy if a source is not found, or may be used in conjunction with sigmoidoscopy in the younger patient.

4.3.4.    Technetium-Labelled Red Blood Cell (99mTc RBC) Scans

The role of nuclear scintigraphic imaging is controversial. It has high sensitivity (up to 85%) and can detect bleeding at a rate as slow as 0.1 mL/min. However, its specificity is low (around 50%), and localization of the bleeding source is often imprecise. Serial scans can be obtained up to 36 hours after injection of the tracer, which may be useful n intermittent bleeding. It is reported to be 10 times more sensitive than mesenteric angiography in detecting ongoing bleeding.

4.4.    Other Investigations

If investigation of the colon has failed to identify a cause of bleeding, evaluation of the upper gastrointestinal tract (e.g. by gastroscopy) may be the most appropriate next step. Helical CT scanning of the abdomen and pelvis may occasionally be helpful. However, despite a range of modalities of investigation, no demonstrable bleeding source is identified in up to 10–20% of patients.

5.    Treatment

The approach to the patient with rectal bleeding will differ depending on the severity of bleeding. The priorities are haemodynamic stabilization, localization of the bleeding site, and the formulation of an interventional plan.

5.1    Minor Intermittent Bleeding

Proctoscopy and rigid sigmoidoscopy can potentially be performed in the ED, although performer experience and adequate bowel preparation need to be considered. After initial assessment, many patients with bleeding or bleeding that has ceased can be investigated on an outpatient basis. Those discharged home should have adequate arrangements for outpatient follow-up with either a surgical or a gastroenterology service. The presence of anorectal pathology requires proximal evaluation of the colon in those aged over 50. The extent of further investigation in the younger age group is dependent on the clinician as well as predisposing factors for malignancy.

5.2.    Major and/or Persistent Rectal Bleeding

Immediate assessment should follow the standard ABC approach, with care to ensure adequate fluid resuscitation, followed by blood products if necessary. A haemodynamically stable, resuscitated patient has less morbidity and improved tolerance of further procedures. Most severe bleeding will cease spontaneously, and further investigation can proceed when the bowel has been properly prepared. In some cases, bleeding continues and active management is required on an emergency basis.

Early colonoscopy preceded by bowel preparation with saline/polyethylene glycol results in improved diagnostic and treatment rates. Technetium-labelled red blood cell scanning and angiography are valuable adjuncts.

5.2.1.    Treatment

Vasopressin may give temporary control of bleeding, with significant reported success. Colonoscopic control of bleeding is achieved in most cases. Risks include re-bleeding and perforation. In addition to proven efficacy, emergency colonoscopy may be the most cost-effective management approach.

Other treatment modalities include electrocoagulation, laser and polypectomy. Most success has been achieved in cases of angiodysplasia, and occasionally with diverticulosis. Transcatheter embolization of angiodysplastic lesions has been reported, but has a significant risk of intestinal ischaemia and infarction. If the bleeding source is unknown, an upper gastrointestinal endoscopy should be considered prior to surgical exploration.

Surgery is most useful as an interval procedure in a resuscitated stable patient for definitive treatment of an established diagnosis. Emergency surgery has a high morbidity and mortality, as patients are usually elderly and haemodynamically unstable. Laparotomy is indicated if the patient continues to bleed and if non-operative management is unsuccessful.

6.    Conclusion

Rectal bleeding is a common problem but rarely acutely life-threatening. Large-volume rectal bleeding can cause shock. Resuscitation should include active intravascular volume replacement with appropriate fluids and blood products. Surgical colleagues should be involved early so that plans can be made regarding appropriate investigation and intervention.

    Adapted from: Textbook of Adult Emergency Medicine E-Book. Authored By Peter Cameron, George Jelinek, Anne-Maree Kelly, Lindsay Murray, Anthony F. T. Brown. Further Readings as cited include:
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