A patient presents with oliguria and elevated BUN/creatinine. What is the likely diagnosis?

• A. Chronic kidney disease
• B. Acute kidney injury
• C. Dehydration without kidney injury
• D. Liver failure

Answer: (B)

Oliguria with rising blood urea nitrogen and creatinine signals that the kidneys are not filtering waste effectively—a sudden decline in kidney function leading to azotemia. This pattern is classic for acute kidney injury, which comes on quickly and presents with decreased urine output and elevated waste products in the blood as the kidneys fail to clear them.

In contrast, chronic kidney disease involves a gradual, long-term loss of kidney function, typically with a history of persistent symptoms and progressive lab changes over time, not an abrupt drop in urine output. Dehydration can cause reduced kidney perfusion and prerenal azotemia with elevated BUN and creatinine, but the scenario emphasizes an actual impairment of kidney function producing oliguria, which points more to acute injury rather than volume depletion alone. Liver failure would not primarily present with this pattern of kidney-specific dysfunction.