BUN/Creatinine ratio differentiate between acute and chronic renal disease. Prerenal azotemia appears when there is poor renal perfusion like hypovolemia, hypotension. Postrenal azotemia is due to obstruction. Prerenal acute failure = BUN/Creatinine ratio > 20 : 1 Renal acute failure = BUN/Creatinine ratio < 20 : 1 Suggest renal azotemia or late postrenal azotemia when BUN / Creatinine ratio = < 10:1 #diagnosis #algorithm #renal #BUN #blood urea nitrogen #creatinine #ratio