Approach

Initial evaluation of the patient includes assessment of the severity of the gastrointestinal (GI) bleeding and of the risk to the patient. Severe lower GI bleeding has been defined as continued bleeding within the first 24 hours of hospitalization (transfusion of ≥2 units of blood and/or hematocrit decrease of ≥20%).[24][25][26] The evaluation of a patient with acute lower GI bleeding involves resuscitation along with diagnostic evaluation and management.

In addition, the following clinical features have been found to be associated with severe bleeding:[24][25][27]

  • Systolic BP <115 mmHg

  • Heart rate >100 bpm

  • Syncope

  • Nontender abdomen

  • Bleeding per rectum during the first 4 hours of presentation

  • Aspirin use

  • More than 2 active comorbid states

  • Shock index ≥1. The shock index is calculated by dividing the patient’s heart rate by the systolic blood pressure and is a marker of hemodynamic instability.

History

The history helps determine the possible source of the GI bleeding and also assesses the severity of the bleeding. Patients can be characterized as being low risk or high risk for complications. Patients with severe bleeding need to be identified early.

The following should be determined from the history:

  • Age of patient. Diverticular disease and angiodysplasia are more common in older patients (age >60 years)[1][9][11][12] 

  • Duration of the bleeding. The bleeding can be either an acute, intermittent or chronic event. Intermittent or chronic rectal bleeding is usually seen in patients with internal hemorrhoids. Acute bleeding, especially in older people, should prompt evaluation for diverticular disease[39]

  • Color of the blood. The color of the blood in the stool, and whether the blood coats the stool or is mixed with the stool, helps to localize the site of bleeding

  • Associated dizziness or syncope. Presence of syncope may suggest that the patient has lost a significant amount of blood

  • Other associated symptoms include abdominal pain, constipation, rectal pain, weight loss, diarrhea, and tenesmus. The presence of abdominal pain and diarrhea with hematochezia (bright red rectal bleeding) suggests colitis, either inflammatory or ischemic, while angiodysplasia does not usually cause pain. Change of bowel habit, tenesmus or weight loss may be seen in colorectal cancer or inflammatory colitis.

  • Specific inquiry about the presence of inflammatory bowel disease, internal hemorrhoids, diverticular disease, angiodysplasia, aspirin/nonsteroidal anti-inflammatory drug (NSAID) use, recent use of antibiotics, and recent travel is required.

Physical exam

Physical exam includes the following:

  • Assessment of vital signs. Assess for postural hypotension. Presence of hemodynamic instability suggests presence of severe bleeding. Mild fever could be present in patients with infectious colitis or inflammatory bowel disease

  • Palpation of the abdomen for tenderness, hepatomegaly or abdominal masses. Hepatomegaly or abdominal masses prompt evaluation for colorectal cancer as the source of the bleeding

  • Rectal exam. It is essential to perform a rectal exam in all patients with lower GI bleeding to exclude a palpable rectal mass. If an anal fissure is suspected and rectal exam would be too painful, consideration of exam under anesthesia is required. The color of the stool may suggest the location of blood loss.

Initial tests

Patients who present in extremis need to be evaluated immediately and urgently treated.

Complete blood count (with major attention to hematocrit, white blood cell (WBC) count, and platelet count), prothrombin time, and thromboplastin time are measured. Patients with acute bleeding, ongoing active bleeding, or severe bleeding require blood group and cross-matching. Erythrocyte sedimentation rate and C-reactive protein may be elevated in patients with inflammatory bowel disease.

Stool studies, such as stool WBC, stool culture, and microscopic exam for ova and parasites, are obtained in patients with hematochezia (bright red rectal bleeding) associated with acute diarrhea.

The US and UK guidelines report risk thresholds for testing for colorectal cancer in symptomatic patients.[40][41][42]​ The US guidelines recommend adults ages <50 years with colorectal bleeding symptoms undergo colonoscopy or evaluation sufficient to determine a bleeding cause.[40]

The UK guidelines recommend certain quantitative fecal immunochemical tests (FITs) to guide referral for suspected colorectal cancer in adults:[41][42]

  • ages <50 years with rectal bleeding and either of unexplained abdominal pain or unintentional weight loss

  • ages ≥50 years with any of unexplained rectal bleeding, unexplained abdominal pain, or unintentional weight loss.

Refer to guidelines for an exhaustive list of signs and/or symptoms that may prompt assessment for colorectal cancer.[40][41]​​[42]​​

Anoscopy

In patients with a suspected anorectal source of bleeding, anoscopy can be a useful diagnostic test. Internal hemorrhoids can be visualized on anoscopy.

Colonoscopy

Colonoscopy is usually the initial imaging procedure in all patients with suspected lower GI bleeding in whom an upper GI or anorectal source has been excluded.[3]​​[27][30]

Colonoscopy can localize the source of the bleeding and also offers potential therapeutic interventions (for instance, colonic angiodysplasia can be treated using conventional endoscopic thermal probes). Early colonoscopy (performed within 24 hours) may potentially improve diagnostic yield in acute lower GI bleeding, but evidence from randomized controlled trials indicates that it does not improve clinical outcomes in these patients.[3][31][32][33][34][35][37] Early colonoscopy may reduce the length of hospital stay.[6][35][37]

Urgent colonoscopy requires a bowel preparation (often with polyethylene glycol solution). The diagnostic yield of colonoscopy in lower GI bleeding ranges from 45% to 100%.[43][44] Complications of colonoscopy include adverse reactions to the intravenous sedative drugs and a low risk of perforation.[45]

Radionuclide imaging: tagged red blood cell scintigraphy, for example, technetium scanning

Radionucleotide imaging may be useful to localize the source of even minimal bleeding (as little as 0.1 mL/minute).[38][46]​ The advantage of this approach is that it is noninvasive. Disadvantages are that it is ineffective if bleeding has ceased, accuracy is variable and dependent on local expertise and experience, and it does not offer any therapeutic potential. It can be used as a screening procedure prior to mesenteric angiography, since patients with a negative scan are unlikely to benefit from angiography.

US consensus guidelines suggest radionuclide imaging (tagged RBC scintigraphy) in:[38]

  • hemodynamically stable patients with evidence of ongoing lower GI bleeding, and

  • negative colonoscopy, and

  • negative CT angiogram (or CT angiogram contraindicated or not available).

Imaging should be continued for one hour to allow detection of intermittent bleeding.[38]​​

Angiography

Angiography requires an active blood loss for a bleeding site to be visualized.

CT angiography (CTA)

The initial test performed in hemodynamically unstable patients.[3][38]​ CTA may also be considered as the first-line study in hemodynamically stable patients if there is high suspicion of active bleeding. CTA yield is low in patients with minor lower GI bleeding.[3]

CTA is the least invasive imaging modality to accurately and rapidly localize a rapidly bleeding site.[3][27][38]​ Disadvantages of CTA include radiation dose and need for intravenous contrast.

Catheter angiography

Recommended when a source of lower GI bleeding is visualized on CTA (or other imaging modality).[3][27]​ Embolization can be used as the primary treatment modality.[3][27][38]​ In most cases, catheter angiography is not indicated if CTA is negative for GI bleeding.[38]

Potential complications of catheter angiography include renal failure, arterial thrombosis, and contrast reactions.

Computed tomography (CT) of the abdomen

CT scan of the abdomen with intravenous and oral contrast is the imaging modality of choice for patients with suspected ischemic colitis.[47]​ Bowel wall thickening, edema, and thumbprinting suggest ischemic colitis. CTA should be performed for patients with suspected isolated right-colon ischemia, or in any patient in whom acute mesenteric ischemia cannot be excluded.[47]

​Typical CT findings in a patient with aortoenteric fistula include: peri-graft fluid, soft tissue attenuation, ectopic gas, pseudo-aneurysm, or focal ischemic bowel.[48]

Esophagogastroduodenoscopy (EGD)

EGD is the diagnostic test of choice to rule out the upper GI tract as the source of the bleeding. It is also useful for the diagnosis of aortoenteric fistula.

Serologic markers (e.g., antinuclear antibodies [ANA], antineutrophil cytoplasmic antibodies [ANCA])

These tests may be performed if the bleeding is suspected to be secondary to a vasculitic disease such as systemic lupus erythematosus.

Venepuncture and phlebotomy: animated demonstration
Venepuncture and phlebotomy: animated demonstration

How to take a venous blood sample from the antecubital fossa using a vacuum needle.

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