BUN-Creatinine ratio

• Pre-renal AKI typically results in BUN:Cr of >20:1 increased resorption of BUN from urine in the proximal tubules, resulting in a disproportionate increase in the serum BUN-creatinine ratio.
• Upper GI bleed is associated with a BUN:Cr of >30:1 resulting from increased BUN production from digestion of blood proteins. The higher the ratio, the greater the likelihood of upper GI bleed.

References:

• MKSAP
• https://www.uptodate.com/contents/approach-to-acute-upper-gastrointestinal-bleeding-in-adults