Urology>>>>>Renal Pathophysiology
Question 4#

Which of the following is TRUE in unilateral ureteric obstruction (UUO)?

A. Renal blood flow (RBF) increases during the first 1 1/2 to 4 hours along with an increase in the ureteric pressure
B. In a second phase lasting between 3 and 5 hours, these pressure parameters remain elevated but RBF begins to rapidly decline
C. A third phase beginning about 5 hours after obstruction is associated with a further drop in RBF and a gradual but small rise in collecting system pressure
D. Infusion of Captopril, an ACE inhibitor attenuates the declines in RBF and GFR in UUO
E. Administration of endothelin antagonists limits the reduction of RBF but increases GFR in rats during and after release of UUO

Correct Answer is D

Comment:

Answer D

In UUO, RBF increases during the first 0–90 minutes and is accompanied by a high collecting system pressure because of the obstruction. In the second phase lasting up to 5 hours, both RBF and collecting system pressure remain elevated but RBF begins to gradually decline. A third phase beginning about 5 hours after obstruction is characterised by a further decline in RBF, now paralleled by a decrease in collecting system pressure.

Infusion of the angiotensin-converting enzyme (ACE) inhibitor Captopril attenuates the declines in RBF and GFR in UUO, suggesting that angiotensin II is an important mediator of the preglomerular vasoconstriction in the second and third phases of UUO. Endothelin antagonists limit the reduction of RBF and GFR in rats during and after release of UUO.