Is esophagogastroduodenoscopy (EGD) or colonoscopy indicated for melena?

EGD is Indicated for Melena; Colonoscopy May Be Considered After Nondiagnostic EGD

Esophagogastroduodenoscopy (EGD) should be performed first in patients presenting with melena, as it represents the primary diagnostic and therapeutic modality for what is typically upper gastrointestinal bleeding. 1, 2 Colonoscopy is indicated only after a nondiagnostic EGD, though its diagnostic yield in this setting is relatively low. 3, 4

Initial Diagnostic Approach

Melena is a clinical diagnosis requiring immediate upper endoscopy without waiting for laboratory confirmation. 1 The characteristic black, tarry, sticky stool with distinctive odor indicates digested blood from the gastrointestinal tract. 1

Immediate Assessment Steps:

• Calculate shock index (heart rate/systolic blood pressure) immediately—a value >1 indicates hemodynamic instability requiring ICU admission 1, 2
• Perform digital rectal examination to confirm melena and exclude anorectal pathology 1, 2
• Check for orthostatic hypotension (drop >20 mmHg systolic or heart rate increase >20 bpm), which indicates significant blood loss 2

Timing and Selection of Endoscopy

For Hemodynamically Unstable Patients:

• Perform CT angiography immediately as the fastest, least invasive means to localize active bleeding 1, 2
• Proceed to EGD or catheter angiography based on CT findings 2

For Hemodynamically Stable Patients:

• Perform EGD within 24 hours as the initial diagnostic procedure 5, 1, 6
• EGD successfully identifies the bleeding source in 95% of cases and facilitates therapeutic intervention 5
• EGD within 12 hours of presentation increases the likelihood of identifying a bleeding source (OR 3.71; 95% CI, 1.05-13.08) 7

Role of Colonoscopy After Nondiagnostic EGD

If EGD is nondiagnostic, colonoscopy should be performed as the next diagnostic step. 5 However, clinicians should understand the limitations:

Diagnostic Yield of Colonoscopy:

• 24% of patients with melena will have nondiagnostic upper endoscopy 4
• Colonoscopy identifies a suspected bleeding source in only 4.8% of patients with melena after nondiagnostic EGD (OR 2.17; 95% CI, 1.65-2.86) 3
• Therapeutic intervention during colonoscopy occurs in only 1.7% of these cases 3
• When a source is found, it is most commonly in the right colon 4

Important Considerations:

• Patients with melena are at increased risk of colorectal cancer (OR 2.87; 95% CI, 1.82-5.51), making colonoscopy valuable even with low bleeding source identification 3
• Colonoscopy can potentially be performed electively in stable patients without continued bleeding 3
• 37% of patients with nondiagnostic EGD will have a source identified on further evaluation, with colonoscopy being the highest-yield test 4

Algorithm for Endoscopic Evaluation

1. Confirm melena by digital rectal examination 1
2. Assess hemodynamic stability (shock index, orthostatic vitals) 1, 2
3. If unstable: CT angiography → catheter angiography or EGD 1, 2
4. If stable: EGD within 24 hours (preferably within 12 hours) 5, 1, 7
5. If EGD nondiagnostic: Colonoscopy after adequate bowel preparation 5, 3, 4
6. If both nondiagnostic: Consider capsule endoscopy for small bowel evaluation 5, 1

Critical Pitfalls to Avoid

• Never delay endoscopy to obtain stool studies—melena is a clinical diagnosis warranting immediate evaluation 1, 6
• Do not assume lower GI source without excluding upper GI bleeding first—failure to perform EGD first leads to delayed diagnosis 1, 2, 6
• Do not confuse simple black stools (from dietary iron, bismuth) with true melena, which has distinctive tar-like consistency and odor 1
• Recognize that massive upper GI bleeding can present as hematochezia rather than melena if transit time is rapid 1
• At INR >7.5, the likelihood of finding an endoscopically significant lesion falls to <20%, suggesting case-by-case decision-making for endoscopy timing 7

Special Populations

Obscure Bleeding After Negative EGD and Colonoscopy:

• Up to 13% of melena cases are due to small intestinal bleeding when upper endoscopy is nondiagnostic 1
• Angiectasia accounts for up to 80% of small bowel sources in obscure bleeding 5, 1
• Small bowel tumors are the most common cause in patients <50 years with obscure bleeding 5, 1
• Capsule endoscopy should be considered for obscure bleeding after negative EGD and colonoscopy 5, 1