This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2018, Subject name: Physiology
GFR is increased by all except? 
Select and explain. 
A. Increased renal blood flow, B. Efferent aeriole constriction, C. Renal stone in ureter, D. Decreased oncotic pressure
C: Renal stone in ureter
Answer: C: Renal stone in ureter 
Explanation: Increased blood flow to glomerular capillaries causes increased capillary hydrostatic pressure causing increased GFR. The efferent aeriole constriction also causes increased capillary hydrostatic pressure causing increased GFR. Plasma colloid oncotic pressure is the force that opposes the filtration; when it is decreased, GFR increased. In case of nephrolithiasis or renal stone, there will be decreased flow of tubular fluid which causes fluid accumulation in Bowman's capsule leading to increased hydrostatic pressure in Bowman's capsule which opposes filtration causing decreased GFR Net filtration pressure = PG -PB - pG PG: glomerular hydrostatic pressure PB: hydrostatic pressure in Bowman's capsule PG: Colloid osmotic pressure of glomerular capillary plasma proteins GFR = KFX net filtration pressure KF = capillary filtration coefficient