Approximately how much blood passes through both kidneys each minute in a resting adult?

• A. About 1.2 L/min (roughly 20–25% of cardiac output)
• B. About 50 mL/min
• C. About 5 L/min
• D. About 120 mL/min

Answer: (A)

Verified step by step guidance

1. Understand that the question asks for the volume of blood passing through both kidneys per minute in a resting adult, which relates to renal blood flow.
2. Recall that cardiac output (CO) is the total volume of blood the heart pumps per minute, typically about 5 liters per minute in a resting adult.
3. Know that the kidneys receive approximately 20–25% of the cardiac output, which means the renal blood flow (RBF) can be calculated as a percentage of the cardiac output.
4. Set up the calculation for renal blood flow using the formula: \(\text{RBF} = \text{CO} \times \text{fraction to kidneys}\), where the fraction is between 0.20 and 0.25.
5. Multiply the cardiac output (about 5 L/min) by the fraction (0.20 to 0.25) to estimate the blood flow through both kidneys per minute.