PAEA Surgery End Of Rotation (EOR) Practice Exam

What is the primary response of the kidneys to decreased blood flow due to renal artery stenosis?

1. Increase in urine output

2. Release of renin

3. Exchange of sodium

4. Decrease in filtration rate

The correct answer is: Release of renin

The primary response of the kidneys to decreased blood flow as seen in renal artery stenosis is the release of renin. When blood flow to the kidneys diminishes, the renal perfusion pressure drops, which is sensed by the juxtaglomerular cells located in the afferent arterioles. In response to this perceived decrease in blood volume or pressure, these cells release renin into circulation. Renin plays a critical role in the renin-angiotensin-aldosterone system (RAAS). It catalyzes the conversion of angiotensinogen, produced by the liver, into angiotensin I. Angiotensin I is then converted to angiotensin II, a potent vasoconstrictor, which increases blood pressure and restores blood flow to the kidneys. Additionally, angiotensin II stimulates the adrenal glands to secrete aldosterone, promoting sodium and water reabsorption, further aiding in increasing blood volume and pressure. This regulatory mechanism is essential for maintaining kidney function and ensuring adequate perfusion even in states of reduced blood flow. The other options, while relevant to kidney function, do not represent the primary acute response to decreased renal perfusion due to renal artery stenosis.