What condition is indicated by the presence of RBC casts in urine?

The presence of red blood cell (RBC) casts in urine is indicative of acute glomerulonephritis. This condition is characterized by inflammation of the glomeruli, which are the tiny filtration units within the kidneys. During acute glomerulonephritis, the glomerular membrane becomes damaged, allowing RBCs to pass through into the urine.

When RBCs aggregate within the renal tubules, they form casts. These casts are important diagnostic features, as they reflect a pathological process occurring in the glomeruli or renal tubules. In acute glomerulonephritis, the RBC casts result from the glomerular inflammation and lead to hematuria (blood in urine), often accompanied by proteinuria and other urinary abnormalities.

The other conditions listed do not typically produce RBC casts. Nephrotic syndrome is marked by significant proteinuria and edema but usually does not present with hematuria or RBC casts. Urinary tract infections generally produce white blood cell casts rather than RBC casts, and acute tubular necrosis is associated with elevated renal tubular damage indicators rather than hematuria or RBC casts. Thus, the presence of RBC casts is a critical finding that strongly points towards acute glomerulonephritis as the