____ is an uncommon cause of acute renal failure due to immune complex deposits in the kidney. Dysmorphic RBC and RBC casts are common.

____ is an uncommon cause of acute renal failure due to immune complex deposits in the kidney. Dysmorphic RBC and RBC casts are common.

• A. Pyelonephritis
• B. Glomerulonephritis
• C. Nephrolithiasis
• D. Hydronephrosis

Answer: (B)

Dysmorphic red blood cells and red blood cell casts come from bleeding at the level of the glomerulus, not from the downstream urinary tract. When immune complexes deposit in the glomeruli, as occurs in glomerulonephritis, the glomerular capillary walls become inflamed and leaky. This injures the filtering unit and allows red blood cells to pass into the urine in a distorted, dysmorphic form, and to form casts as they mix with Tamm-Horsfall protein in the tubules. This pattern—hematuria with dysmorphic RBCs and RBC casts—points to glomerular disease and can contribute to acute renal failure by reducing filtration. In contrast, infection of the renal pelvis or kidney tissue (pyelonephritis) typically presents with fever, flank pain, and pus cells in urine, but red cells are usually not dysmorphic and RBC casts are less characteristic. Hematuria from nephrolithiasis (stones) is common but RBCs are not specifically dysmorphic and the process is more about mucosal irritation than glomerular injury. Hydronephrosis reflects obstructive backpressure with broad-based kidney dysfunction but not the pattern of glomerular immune complex injury. So the presence of dysmorphic RBCs and RBC casts, along with acute renal impairment due to immune complex–mediated injury, points to glomerulonephritis.

Dysmorphic red blood cells and red blood cell casts come from bleeding at the level of the glomerulus, not from the downstream urinary tract. When immune complexes deposit in the glomeruli, as occurs in glomerulonephritis, the glomerular capillary walls become inflamed and leaky. This injures the filtering unit and allows red blood cells to pass into the urine in a distorted, dysmorphic form, and to form casts as they mix with Tamm-Horsfall protein in the tubules. This pattern—hematuria with dysmorphic RBCs and RBC casts—points to glomerular disease and can contribute to acute renal failure by reducing filtration.

In contrast, infection of the renal pelvis or kidney tissue (pyelonephritis) typically presents with fever, flank pain, and pus cells in urine, but red cells are usually not dysmorphic and RBC casts are less characteristic. Hematuria from nephrolithiasis (stones) is common but RBCs are not specifically dysmorphic and the process is more about mucosal irritation than glomerular injury. Hydronephrosis reflects obstructive backpressure with broad-based kidney dysfunction but not the pattern of glomerular immune complex injury.

So the presence of dysmorphic RBCs and RBC casts, along with acute renal impairment due to immune complex–mediated injury, points to glomerulonephritis.