RBC casts in urine are most strongly associated with which renal condition?

RBC casts in urine are most strongly associated with which renal condition?

• A. Acute tubular necrosis
• B. Glomerulonephritis
• C. Pyelonephritis
• D. Hydronephrosis

Answer: (B)

RBC casts form when red blood cells leak through damaged glomerular capillaries and enter the tubular lumen, where they mix with Tamm-Horsfall protein to form casts. This makes RBC casts a hallmark of glomerular inflammation or injury, as seen in glomerulonephritis, where hematuria and red cells pass into the filtrate and are carried down the tubules to become casts. In this context, the presence of RBC casts signals that the primary problem is at the level of the glomerulus, causing red cells to appear in the urine and be recast within the tubular system. In contrast, other conditions typically produce different casts: acute tubular necrosis tends to yield granular or epithelial cell casts from tubular injury; pyelonephritis more commonly shows white blood cell casts reflecting tubular inflammation from infection; hydronephrosis is obstruction-related and usually shows a bland sediment with possible crystals or bacteria, not RBC casts as a defining feature.

RBC casts form when red blood cells leak through damaged glomerular capillaries and enter the tubular lumen, where they mix with Tamm-Horsfall protein to form casts. This makes RBC casts a hallmark of glomerular inflammation or injury, as seen in glomerulonephritis, where hematuria and red cells pass into the filtrate and are carried down the tubules to become casts. In this context, the presence of RBC casts signals that the primary problem is at the level of the glomerulus, causing red cells to appear in the urine and be recast within the tubular system.

In contrast, other conditions typically produce different casts: acute tubular necrosis tends to yield granular or epithelial cell casts from tubular injury; pyelonephritis more commonly shows white blood cell casts reflecting tubular inflammation from infection; hydronephrosis is obstruction-related and usually shows a bland sediment with possible crystals or bacteria, not RBC casts as a defining feature.