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Obstructed kidneys with decreased function prior to pyeloplasty have marginal improvement in function postoperatively
Kristin M. Ebert, MD, Venkata R. Jayanthi, MD, Daryl J. McLeod, MD.
Nationwide Children's Hospital, Columbus, OH, USA.

Background:There is conflicting data in the literature regarding factors influencing recovery of function after pyeloplasty in patients with ureteropelvic junction obstruction (UPJO) and decreased differential renal function. We aimed to determine functional outcomes after pyeloplasty in patients with UPJO and decreased renal function (≤40% preoperative differential function), and to ascertain predictors of improvement in function.
Methods:We performed a retrospective single center review of all patients who underwent pyeloplasty for UPJO between 1998-2018. Only patients with at least one preoperative and one postoperative renogram, and a differential function of 40% or less of the obstructed kidney on preoperative renogram were included. We excluded patients with solitary kidney, bilateral UPJO, duplicated upper tracts, redo pyeloplasty, and any drainage procedure prior to pyeloplasty. Primary outcome of interest was change in function of the obstructed kidney after pyeloplasty. We also evaluated if age, preoperative renal function, and presence of prenatal hydronephrosis were correlated with change in function by calculating a Pearson correlation coefficient. Lastly, we evaluated if preoperative renal function had an effect on change in function using one-way ANOVA (see table).
Results:In total, 467 patients underwent pyeloplasty in the study period; 66 of these met inclusion criteria. Mean age was 58.4 months (range 1.7-221.9); 60.6% were male. Prenatal hydronephrosis was present in 56.1%. Pyeloplasty was performed in an open fashion in 42.4%, laparoscopically in 48.5%, and robotically in 9.1%. Mean preoperative differential function of the obstructed kidney was 29.2% (range 5-40%). Mean postoperative differential function of the obstructed kidney was 32.5% (range 0-56%), for a mean improvement of 3.3% (range -37% to +25%). Overall, 60.6% of patients did have some improvement in differential function of their obstructed kidney postoperatively. Of patients who did improve, the mean improvement was 9.7% (range 0.3-25%). In the overall cohort, there was no significant correlation between age and change in function (r=0.14, p=0.27), nor preoperative differential function of the obstructed kidney and change in function (r=-0.56, p=0.65). When patients were divided into four groups based on preoperative renal function, there were no significant differences between group means (F(3,62)=0.17, p = 0.92). There was a trend toward greater improvement in function in patients with prenatal hydronephrosis (4.5% improvement vs. 1.6% improvement in patients without prenatal hydronephrosis), but this did not reach statistical significance (p=0.31).
Conclusions:Obstructed kidneys with decreased function prior to pyeloplasty have overall marginal improvement in differential function postoperatively. However, patients who have improvement in function do tend to have considerable (approximately 10%) improvement from their baseline. Patient age and preoperative differential function of the obstructed kidney do not correlate with change in function after pyeloplasty. Patients with prenatally detected UPJO may have the opportunity for greater improvement in function after pyeloplasty than patients with symptomatic UPJO. 

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