Dispropoionately increased blood urea levels compared to serum creatinine (urea creatinine ratio 20:1) can be seen in the following except -

Intrinsic or intrarenal acute renal failure (ARF) occurs when direct damage to the kidneys causes a sudden loss in kidney function. The most common causes of intrinsic acute renal failure are acute tubular necrosis (ATN), acute glomerulonephritis (AGN), and acute interstitial nephritis (AIN) . Ref Harrison20th edition pg 236