Q: How upper gastrointestinal bleed (UGIB) can be differentiated from lower gastrointestinal bleed (LGIB) by looking at Basic Metabolic Profile (BMP)?
Answer: Patients with acute lower GI bleeding, and with normal kidney function, usually have a normal blood urea nitrogen (BUN)-to-creatinine (Cr). In contrast, patients with acute upper GI bleeding with normal renal function will have higher BUN/Cr ratio.
Mortensen PB, Nøhr M, Møller-Petersen JF, Balslev I. The diagnostic value of serum urea/creatinine ratio in distinguishing between upper and lower gastrointestinal bleeding. A prospective study. Dan Med Bull 1994; 41:237.