A 68-year-old woman with heart failure presents with tachycardia, S3 heart sound and basilar crackles bilaterally. BP is 90/68 mmHg; BUN is 58 mg/dL (20.7 mmol/L); creatinine level is 2.4 mg/dL. This clinical presentation is most consistent with:
A. Prerenal azotemiaB. Acute glomerulonephritisC. Tubular necrosisD. Postrenal azotemia

A. Prerenal azotemia

Explanation:

Prerenal azotemia is the most common type of acute renal failure. Prerenal azotemia is a condition where the kidneys are hypoperfused, this leads to acute tubular necrosis. This hypoperfusion is as a result of decreased circulating volume especially for patient with dehydration and blood loss, decreased cardiac output (seen in patients with heart failure) and excessive sequestering of fluids for patient with burns. For prerenal azotemia BUN:creatinine(cr) ratio > 20:1. In this case BUN is 58 mg/dL (20.7 mmol/L); creatinine level is 2.4 mg/dL, therefore BUN/cr = 58:2.4 = 24.17:1

Laboratoty findings for some disease are: