Purpose: We assessed the renal blood flow pattern in experimental hydroneph
rosis during normal hydration and extracellular volume expansion.
Materials and Methods: Partial obstruction of the left ureter was created i
n 3-week-old Sprague-Dawley rats by embedding the ureter in a psoas muscle
groove. Moderate hydronephrosis without kidney weight reduction developed i
n all cases. The effects on renal hemodynamics were studied with real-time
ultrasound flowmetry 3 weeks later during normal hydration and then during
volume expansion. The degree of hydronephrosis was classified as mild, mode
rate or severe.
Results: Under baseline conditions renal blood flow was normal in mild and
moderate hydronephrosis but low in severe hydronephrosis, During volume exp
ansion renal blood flow increased significantly in all experimental animals
(mean 14%) compared to that in controls, which remained unaffected or decr
eased (mean -3%). The flow increase was related to the degree of dilatation
, which was 2% in mild, 13% in moderate and 44% in severe hydronephrosis wh
en the groups were considered separately.
Conclusions: A significant increase in renal blood flow proportional to the
degree of hydronephrosis occurred as a result of volume expansion. This fi
nding may be explained by a st-ate of vasodilatation combined with a reduct
ion in the filtration coefficient.