In a person with hematuria, which process of urine formation is ineffective?

• A. Filtration
• B. Secretion
• C. Reabsorption
• D. Excretion

Answer: (A)

When blood cells appear in urine, the issue points to the filtration step in the kidneys. The glomerular filtration barrier normally separates cells and large proteins from the filtrate, letting only fluid and small solutes pass into Bowman's space. If this barrier is damaged or otherwise ineffective, red blood cells can slip into the filtrate, producing hematuria. Reabsorption and secretion modify the composition of filtrate after it’s formed but aren’t the primary cause of blood appearing in urine. Excretion is simply the final elimination of waste; a problem there wouldn’t explain RBCs in the urine. So the process that’s ineffective here is filtration.