Which statement correctly describes systemic clearance compared to renal clearance?

• A. Systemic clearance equals renal clearance
• B. Systemic clearance is the sum of all routes of elimination; renal clearance is only via kidneys
• C. Systemic clearance equals hepatic clearance only
• D. Renal clearance is always greater than systemic clearance

Answer: (B)

Systemic clearance reflects the body's overall ability to remove a drug from the plasma, incorporating all elimination pathways. Renal clearance, on the other hand, is only the portion cleared by the kidneys. So systemic clearance is the sum of all routes of elimination (renal, hepatic, pulmonary, etc.), whereas renal clearance is just the renal component. This is why the statement that captures the total clearance as the sum of all routes is correct. The kidney’s role is just one piece of the total; other pathways can contribute substantially, and only in a scenario where the kidneys are the sole route would systemic clearance equal renal clearance.