The presence of RBC casts on spun urine sediment is pathognomonic for which condition?

The presence of RBC casts on spun urine sediment is pathognomonic for which condition?

• A. Acute pyelonephritis
• B. Acute glomerulonephritis
• C. Acute interstitial nephritis
• D. Acute tubular necrosis

Answer: (B)

RBC casts indicate bleeding from the glomerulus. Red blood cells enter the filtrate when the glomerular basement membrane or capillary walls are damaged, and they can form casts in the tubules. This pattern is classic for a nephritic process, with acute glomerulonephritis being the primary example. In contrast, pyelonephritis usually shows white blood cell casts (and bacteria), acute interstitial nephritis often has eosinophils and WBC casts, and acute tubular necrosis typically yields granular (muddy brown) casts. So the presence of RBC casts best points to an acute glomerulonephritis.

RBC casts indicate bleeding from the glomerulus. Red blood cells enter the filtrate when the glomerular basement membrane or capillary walls are damaged, and they can form casts in the tubules. This pattern is classic for a nephritic process, with acute glomerulonephritis being the primary example. In contrast, pyelonephritis usually shows white blood cell casts (and bacteria), acute interstitial nephritis often has eosinophils and WBC casts, and acute tubular necrosis typically yields granular (muddy brown) casts. So the presence of RBC casts best points to an acute glomerulonephritis.