Normal differential renal function does not indicate a normal kidney after partial ureteropelvic obstruction and subsequent relief in 2-week-old piglets

Purpose  We investigated the functional consequences of relieving ureteric obstruction in young pigs with experimental hydronephrosis (HN) induced by partial unilateral ureteropelvic obstruction. Materials and methods  Three groups of animals were followed from the age of 2 weeks to the age of 14 weeks: Eight animals had severe or grades 3–4 HN throughout the study. Six animals had relief of the obstruction after 4 weeks. Six animals received sham operations at both ages. Morphological and functional examinations were performed at age 6 weeks and again at age 14 weeks and consisted of magnetic resonance imaging (MRI), technetium-diethylenetriaminepentaaceticacid (^99mTc-DTPA) renography, renal technetium-dimercaptosuccinicacid (^99mTc-DMSA) scintigraphy, and glomerular filtration rate (GFR) measurement. Results  After relief of the partial obstruction, there was reduction of the pelvic diameter and improvement of urinary drainage. Global and relative kidney function was not significantly affected by either obstruction or its relief. Renal ^99mTc-DMSA scintigraphy showed a change in both the appearance of the kidney and a change in the distribution within kidneys even after relief of obstruction. Conclusion  This study shows that partial ureteric obstruction in young pigs may be associated with little effect on global and differential kidney function. However, even after relief of HN, the distribution of ^99mTc-DMSA in the kidney remains abnormal suggesting that a normal differential renal function may not represent a normal kidney.