A 28-year-old woman with a 10-year history of type 1 diabetes presents with microalbuminuria. Her measured GFR is 150 mL/min (elevated). Which pathophysiological change in the glomerulus is most directly responsible for the hyperfiltration in early diabetic nephropathy?

• A Preferential efferent arteriolar constriction mediated by angiotensin II ✓
• B Increased glomerular capillary oncotic pressure due to protein leakage
• C Loss of podocyte slit diaphragm proteins reducing filtration fraction
• D Decreased tubular reabsorption leading to tubuloglomerular feedback activation

Explanation

In early diabetic nephropathy, hyperfiltration results from preferential efferent arteriolar constriction (driven by angiotensin II and other mediators), raising glomerular capillary hydrostatic pressure. This is the central mechanism targeted by ACE inhibitors. Distractor B is wrong because oncotic pressure falls (not rises) with hyperfiltration. Distractor C describes later nephrotic changes, not early hyperfiltration.

Reference: Brenner and Rector's The Kidney, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.