Upper pole pathologies in duplex kidneys: an analysis of predictive factors for surgery and urinary tract infections from the Mid-Atlantic Pediatric Academic Consortium

Abstract

Background/objective: While there is significant data on the natural history and outcomes for prenatal hydronephrosis in simplex kidneys, duplex kidneys tend to be less studied. Management can be quite variable based on provider preference. We aimed to describe practice patterns from several tertiary academic institutions, identify clinical predictors for surgical intervention and urinary tract infection (UTI) for upper pole pathology, and demonstrate the natural history of lower pole vesicoureteral reflux (VUR).

Methods: We conducted a retrospective review of patients from 4 Mid-Atlantic institutions between 2015 and 2020. Inclusion criteria included patients with a duplex kidney with upper pole pathology and/or lower pole VUR. The primary outcome was predictive factors for surgical intervention and UTI. The secondary outcome was to assess the natural history of lower pole VUR including resolution rates by grade. Linear regression identified clinical predictors for UTI events. Multivariate logistic regression identified predictors of surgical intervention, UTI, and lower pole VUR resolution. Descriptive statistics and regression modeling analyses were performed using SAS.

Results: Two hundred forty-two patients were included with a total of 271 duplex renal units. Hydronephrosis grade (both SFU and UTD grading) and number of prior UTI events were statistically significant predictors for surgical intervention (p = 0.03/0.001 and p = 0.002 respectively). Ectopic ureter (p = 0.004), ureterocele (p = 0.02), and obstruction (p = 0.04) were the only pathologies predictive for surgery. Male gender and circumcision were significantly associated with decreased UTI risk (p = 0.03 and p = 0.01). On linear regression modeling, antibiotic prophylaxis after the first year of life was associated with decreased risk of further UTI events (p = 0.03); however, antibiotic prophylaxis within the first year of life did not decrease UTI risk (p = 0.14). For VUR outcomes, 65.0% of grades 1-3 VUR and 52.2% of grades 4-5 had resolution/improvement at mean time of 2.1 years. There were no predictive factors for resolution/improvement of VUR.

Conclusions: Hydronephrosis grade and UTI events were significant predictors for surgical intervention for upper pole pathology. Pathologies that were predictive for surgery included ectopic ureter, ureterocele and obstruction. Male gender, circumcision and antibiotic prophylaxis after the first year of life were associated with a decreased UTI risk. Roughly 58% of lower pole VUR spontaneously improved/resolved. Identification of these risk factors aids in standardization of care practices to reduce long-term UTI risk and inform counseling with families about possible need for surgical intervention and expectations for long term outcomes.

Keywords: Duplex kidney; Ectopic ureter; Ureterocele; Vesicoureteral reflux.