Evidence‑Based Assessment and Diagnosis of Melena

Definition and Anatomical Correlates

• Melena is defined as the passage of black, tarry stools resulting from digested blood; it is identified through clinical assessment, characteristic stool appearance, and confirmatory testing. 1
• The condition specifically reflects upper gastrointestinal bleeding, with blood having been digested and oxidized during transit, and most commonly originates proximal to the ligament of Treitz. 3

Clinical Assessment

Stool Examination

• True melena exhibits a distinctive black, tarry, sticky consistency and a foul odor caused by hemoglobin degradation by gastric acid and intestinal bacteria. 1

Digital Rectal Examination (DRE)

• Performing a DRE in every patient with suspected melena is essential to directly evaluate stool color, consistency, and tarry quality. 5

Laboratory Confirmation

Fecal Occult Blood Testing

• Fecal occult blood testing reliably confirms the presence of blood in stool, thereby distinguishing true melena from non‑bleeding dietary or medication causes. 2

Hemoglobin/Hematocrit Evaluation

• Measurement of hemoglobin and hematocrit provides objective evidence of blood‑loss anemia in patients presenting with melena. 6

Blood Urea Nitrogen (BUN) Assessment

• An elevated BUN level disproportionate to creatinine is indicative of upper gastrointestinal bleeding, reflecting absorption of digested protein from the bleed. 6

Associated Clinical Findings

Upper GI Bleeding Signs

• The presence of hematemesis or coffee‑ground emesis strongly supports an upper gastrointestinal source of bleeding and confirms true melena. 4

Hemodynamic Indicators

• Hemodynamic instability—manifested as tachycardia and hypotension—signals significant blood loss consistent with true melena. 6