Question

In hypovolemic shock, which of the following renal vascular changes occurs?

• A. Afferent arteriolar constriction
• B. Efferent arteriolar constriction
• C. Increased blood flow to kidney
• D. Normal cardiac output

Hint:

Sympathetic and angiotensin surge clamps the inflow arteriole to the glomerulus.

Answer 1

The Correct Option is A

Step 1: Hypovolemic shock means an inadequate circulating blood volume from fluid loss (hemorrhage, salt and water loss, sepsis, burns). Poor venous return lowers stroke volume and cardiac output.
Step 2: The body compensates with tachycardia and a generalized rise in systemic vascular resistance (SVR), mediated by the sympathetic nervous system and the renin-angiotensin system. Patients become cold and shut down peripherally.
Step 3: In the kidney this sympathetic and angiotensin-driven vasoconstriction acts strongly on the afferent arteriole, reducing renal blood flow and glomerular filtration to help shunt blood to vital organs. So option (a), afferent arteriolar constriction, is correct.
Step 4: The other options are wrong: efferent constriction is the angiotensin-predominant response that tends to preserve GFR in milder volume depletion, not the dominant feature of frank shock; blood flow to the kidney falls (it does not increase); and cardiac output is reduced, not normal.