Blood Urea Nitrogen to Creatinine Ratio as a Predictor of Upper or Lower Source of Melena: A Prospective Study

Background: In the evaluation of gastrointestinal (GI) bleeding, accurately identifying whether the source is upper or lower GI is critical for timely and appropriate management. However, determining the bleeding origin can be particularly challenging in cases of isolated melena without hematemesis. Non-invasive, cost-effective diagnostic tools that can aid in early localization are therefore of significant clinical value. <i>Objective:</i> This study aimed to assess the diagnostic performance of the blood urea nitrogen (BUN) to creatinine ratio as a predictor of the bleeding source—upper vs. lower GI—in patients presenting with isolated melena. <i>Methods:</i> We conducted a prospective study involving patients who presented with melena in the absence of hematemesis. Laboratory values including BUN and creatinine levels were collected, and the BUN/creatinine ratio was calculated. Endoscopic evaluations were subsequently performed to determine the actual source of bleeding. <i>Results:</i> Our findings showed that a BUN/creatinine ratio below 50 was highly predictive of upper GI bleeding. In contrast, patients with lower GI bleeding demonstrated significantly higher BUN/creatinine ratios. The ratio proved to be a reliable, non-invasive biochemical marker that could assist in predicting the bleeding source prior to endoscopy. <i>Conclusion:</i> The BUN/creatinine ratio offers a simple, accessible, and effective means to guide clinical triage in patients with isolated melena. Its use could enhance early decision-making and improve patient outcomes by facilitating prompt diagnostic and therapeutic interventions.