From the Guidelines
Investigation for melena should begin with a thorough history and physical examination, followed by laboratory tests and an upper endoscopy (EGD) within 24 hours of presentation, as it can identify the source of bleeding in approximately 75% of cases. This approach is supported by the American College of Gastroenterology practice guidelines, which emphasize the importance of prompt evaluation and treatment of upper gastrointestinal bleeding (UGIB) [ 1 ]. The initial assessment should include laboratory tests such as complete blood count, coagulation profile, and iron studies to assess for anemia and bleeding severity.
Key Investigations
- Upper endoscopy (EGD) within 24 hours of presentation
- Laboratory tests: complete blood count, coagulation profile, and iron studies
- Colonoscopy if EGD is negative to rule out right-sided colonic sources
- Additional studies such as video capsule endoscopy, CT angiography, or technetium-99m-labeled red blood cell scintigraphy if endoscopy fails to identify the source
According to the study by Singh-Bhinder et al [ 1 ], upper endoscopy and video capsule endoscopy (VCE) are two of the most important diagnostic techniques in the investigation of UGIB. While VCE is not performed as a radiology examination, it can be useful in evaluating the small bowel for potential sources of bleeding. The study also highlights the importance of aggressive volume resuscitation and maintenance of hemodynamic stability in patients presenting with substantial UGIB [ 1 ].
Clinical Considerations
- Patients with hemodynamic instability require urgent intervention, including fluid resuscitation and blood transfusion if hemoglobin is below 7 g/dL
- Identifying and addressing risk factors such as NSAID use, anticoagulants, or H. pylori infection is essential for preventing recurrence once the acute bleeding is controlled
- The timing and sequence of investigations should be guided by the patient's clinical stability, with unstable patients requiring more rapid evaluation and intervention.
From the Research
Investigations for Melena
The investigations for melena, or black tarry stools, typically involve a combination of endoscopic and imaging studies to identify the source of bleeding. Some of the key investigations include:
- Esophagogastroduodenoscopy (EGD) to visualize the upper gastrointestinal tract 2, 3
- Colonoscopy to evaluate the lower gastrointestinal tract, especially if EGD is nondiagnostic 4, 3
- Small bowel capsule endoscopy to investigate bleeding in the small intestine, particularly if other tests are inconclusive 2, 5
- Abdominal ultrasonography to assess for any abnormalities in the gastrointestinal tract or surrounding organs 2
Factors Indicating Bleeding Source
Certain factors can indicate the likelihood of finding a bleeding source in specific locations, such as:
- Vomiting, abnormal abdominal ultrasonography findings, and low hemoglobin levels may suggest a bleeding source in the upper gastrointestinal tract 2
- Presence of melena may predict bleeding in the proximal small intestine 5
- Patients with microcytic anemia and positive Hemoccult test have a higher chance of finding a potential bleeding source 3
Diagnostic Yield and Therapeutic Intervention
The diagnostic yield and rate of therapeutic intervention during colonoscopy for melena after a nondiagnostic EGD are relatively low, with a suspected bleeding source found in 4.8% of patients and therapeutic intervention required in 1.7% of cases 4. However, colonoscopy can still be useful in identifying bleeding sources, especially in patients at increased risk of colorectal cancer.