In a patient with lupus, urinalysis shows protein 3+, large blood, and red cell casts 3-5; these findings are most associated with which condition?

In a patient with lupus, urinalysis shows protein 3+, large blood, and red cell casts 3-5; these findings are most associated with which condition?

• A. Glomerulonephritis
• B. Acute tubular necrosis
• C. Acute pyelonephritis
• D. Strenuous exercise

Answer: (A)

Red blood cell casts signal glomerular injury. When the glomeruli are inflamed or damaged, red blood cells leak into the filtrate and can form casts in the tubules; their presence is a hallmark of glomerulonephritis. In systemic lupus erythematosus, lupus nephritis is a classic immune complex–mediated glomerulonephritis, so this urinalysis pattern (heavy protein, gross hematuria, and RBC casts) fits glomerulonephritis best. Acute tubular necrosis typically shows muddy brown granular casts rather than RBC casts and less prominent hematuria. Acute pyelonephritis often has white blood cell casts and bacteria. Strenuous exercise can cause transient, mild proteinuria and hematuria without RBC casts.

Red blood cell casts signal glomerular injury. When the glomeruli are inflamed or damaged, red blood cells leak into the filtrate and can form casts in the tubules; their presence is a hallmark of glomerulonephritis. In systemic lupus erythematosus, lupus nephritis is a classic immune complex–mediated glomerulonephritis, so this urinalysis pattern (heavy protein, gross hematuria, and RBC casts) fits glomerulonephritis best.

Acute tubular necrosis typically shows muddy brown granular casts rather than RBC casts and less prominent hematuria. Acute pyelonephritis often has white blood cell casts and bacteria. Strenuous exercise can cause transient, mild proteinuria and hematuria without RBC casts.