Which condition leads to lipid casts and oval fat bodies in urine?

• A. Nephrotic syndrome
• B. Acute tubular necrosis
• C. Acute glomerulonephritis
• D. Nephritic syndrome

Answer: (A)

Lipid casts and oval fat bodies in urine signal nephrotic-range proteinuria. When glomerular permeability is greatly increased, the kidneys lose large amounts of protein in the urine. In response, the liver ramps up lipoprotein production, causing hyperlipidemia and lipid-rich filtered material. Renal tubular cells take up these lipids and become laden with fat, appearing as oval fat bodies, and lipid droplets can also be seen within casts, forming lipid casts. This combination is a classic clue for nephrotic syndrome, where heavy protein loss drives the lipiduria.

In contrast, conditions like acute tubular necrosis show granular "muddy brown" casts from tubular injury, and nephritic syndromes (including acute glomerulonephritis) typically feature red blood cell casts and only modest proteinuria rather than lipid-rich casts.