A clinical nomogram for predicting postoperative renal function improvement in children with UPJO

Ureteropelvic junction obstruction (UPJO) is an important cause of congenital hydronephrosis and may result in impaired differential renal function (DRF) if not addressed in a timely fashion. Although pyeloplasty is generally effective, postoperative renal functional improvement varies among patients. Validated tools to estimate the probability of renal function improvement after surgery remain limited. Therefore, this study aimed to develop and externally validate a nomogram to predict postoperative renal function improvement in children with UPJO undergoing pyeloplasty.

We conducted a two-center retrospective study including UPJO patients under 16 years of age who underwent laparoscopic dismembered pyeloplasty, with or without robotic assistance. Clinical, imaging, and laboratory data were collected. Development-cohort patients had non-diuretic 99mTc-DTPA dynamic renal scintigraphy, while validation-cohort patients had diuretic 99mTc-DTPA dynamic renal scintigraphy, preoperatively and at postoperative follow-up. Renal function improvement was defined as a ≥5 % increase in affected-side DRF. Predictors were identified using least absolute shrinkage and selection operator (LASSO) and logistic regression analyses, and a nomogram was subsequently constructed. Model performance was assessed using the area under the curve (AUC), calibration plots, the Hosmer-Lemeshow test, and decision curve analysis (DCA).

A total of 148 patients were included in the development cohort, and 30 in the external validation cohort. Demographic and baseline characteristics, laboratory and urinalysis findings, renal morphological and functional parameters, and surgical/perioperative variables, were collected and analyzed. Serum urea (UREA), preoperative anteroposterior diameter, preoperative affected-side glomerular filtration rate (GFR) and DRF, and the affected-to-contralateral GFR ratio were associated with postoperative DRF improvement. Combined with the LASSO regression and clinical relevance, the final nomogram incorporated gender, age (≥12 months vs. <12 months), preoperative affected-side DRF, and UREA. The nomogram demonstrated good performance, with AUCs of 0.836 in the development cohort and 0.880 in the validation cohort.

Most pediatric patients with UPJO demonstrate stabilization or modest improvement in renal function following pyeloplasty, with more pronounced benefits observed in those with lower preoperative DRF. The proposed nomogram provides individualized probability estimates of postoperative functional improvement, which may aid preoperative counseling and expectation setting.