Approximately how much blood flows through both kidneys per minute in a healthy adult at rest?

• A. About 0.05 L/min (approximately 1% of cardiac output)
• B. About 3.5 L/min (approximately 70% of cardiac output)
• C. About 0.25 L/min (approximately 5% of cardiac output)
• D. About 1.2 L/min (approximately 20–25% of cardiac output)

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the concept of cardiac output, which is the total volume of blood the heart pumps per minute. In a healthy adult at rest, the average cardiac output is approximately 5 liters per minute.
2. Step 2: Recognize that the kidneys receive a significant portion of this cardiac output because they play a crucial role in filtering blood and maintaining homeostasis.
3. Step 3: Recall that the renal blood flow to both kidneys combined is about 20–25% of the total cardiac output. This means the kidneys receive roughly one-fifth to one-quarter of the blood pumped by the heart each minute.
4. Step 4: Calculate the approximate blood flow through both kidneys by multiplying the cardiac output by the percentage of blood flow to the kidneys. Use the formula: \(\text{Renal Blood Flow} = \text{Cardiac Output} \times \text{Fraction to Kidneys}\).
5. Step 5: Substitute the values into the formula: \(\text{Renal Blood Flow} = 5\, \text{L/min} \times 0.20\) to \$0.25$, which will give the range of blood flow through both kidneys per minute.