Diagnostic Test Characteristics of Renal Ultrasound Findings for High-Risk Bladder in Spina Bifida.

Abstract

Spina bifida (SB) can cause neurogenic bladder dysfunction and renal deterioration. Guidelines recommend renal ultrasound (RUS) for surveillance, but its utility in screening for high-risk bladder is unclear. We evaluated the performance of RUS findings for detecting high-risk bladder in youth with SB. We conducted a retrospective cohort study of patients with myelomeningocele at a pediatric SB clinic who had a RUS within three months of urodynamic studies (UDS). RUS parameters included hydronephrosis, thinned parenchyma, hypoplasia, and scarring. High-risk bladder was defined as end-fill pressures/detrusor leak point pressures of 40 cmH2O or greater. We calculated sensitivity, specificity, and overall diagnostic accuracy (AUC) of RUS parameters for high-risk bladder, adjusting for repeat measurements. Various subgroup and sensitivity analyses were performed. We analyzed 575 UDS-RUS dyads from 244 unique patients. Median age was 7.2 years, 70% had ventricular shunts. 25% of dyads had high-risk bladder. Any hydronephrosis by Society for Fetal Urology (SFU) grading demonstrated an overall sensitivity 50%, specificity 57%, and clustered AUC of 55% for detecting high-risk bladder. RUS had similar performance across additional analyses, including non-ambulatory patients, high-grade hydronephrosis (SFU 3-4), any RUS abnormality, and using Urinary Tract Dilation (UTD) grading instead of SFU grading. Any hydronephrosis had higher test sensitivity for high-risk bladder in fuller bladders on RUS (RUS-bladder volume >75% of UDS-bladder capacity). RUS should not be used alone as a screening tool to identify high-risk bladder in youth with SB given its limited sensitivity and diagnostic utility. UDS remains an essential and necessary tool for surveilling at-risk bladders.