Diagnostic Test Characteristics of Ultrasound-Based Hydronephrosis for Chronic Kidney Disease in Children and Adolescents With Myelomeningocele: Results From the UMPIRE and National Spina Bifida Patient Registry Cohort Studies.

Purpose: Renal ultrasounds are performed in patients with myelomeningocele to screen for markers of kidney health, including hydronephrosis. We evaluated the diagnostic accuracy of hydronephrosis to screen for low kidney function defined by estimated glomerular filtration rate (eGFR).

Materials and methods: We performed a retrospective cross-sectional study using data from 2 cohorts of children and youth with myelomeningocele. The first cohort is from UMPIRE (2016-2022) and the second from the National Spina Bifida Patient Registry (NSBPR; 2009-2021). We identified patients aged 1 to 18 years with available eGFR data within 6 months of an ultrasound. We excluded NSBPR patients younger than 6 years to address potential duplication across cohorts. The primary outcome was eGFR < 90 mL/min/1.73 m², calculated using the bedside Schwartz formula. Hydronephrosis was dichotomized into any/none. We calculated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of any hydronephrosis using eGFR as the reference standard.

Results: In UMPIRE, 221 patients were included with median age 2.4 years (IQR, 1.9-3.8) and 24% having eGFR < 90. Any hydronephrosis vs none conferred a sensitivity/specificity/PPV/NPV of 25%/75%/24%/77%, respectively. In NSBPR, 2269 patients were included with median age 13 years (IQR, 9.6-16.3) and 17% having eGFR < 90. Any hydronephrosis vs none conferred a sensitivity/specificity/PPV/NPV of 24%/87%/26%/85%, respectively.

Conclusions: In 2 cohorts of children and youth with myelomeningocele, hydronephrosis conferred a sensitivity of ∼25% for a creatinine-based eGFR < 90 mL/min/1.73 m². This low sensitivity suggests that hydronephrosis alone is a poor screening marker of kidney health.