Renal parenchymal thickness measurements on initial sonogram are associated with spontaneous resolution of isolated...

Measurements of the renal parenchyma have been associated with risk for undergoing pyeloplasty in children with antenatally diagnosed isolated hydronephrosis.

To evaluate the association of renal parenchymal measurements and spontaneous resolution of isolated SFU grade 3 hydronephrosis.

A retrospective single-institution cohort of patients with antenatally diagnosed SFU grade 3 hydronephrosis without hydroureter from 2000 to 2016 was identified. Those with adequate follow-up, defined as two sonograms, and renal measurements performed were included for analysis. Final hydronephrosis grade prior to 5 years of age was the primary outcome; resolution was defined as SFU grade 0-1 and improvement as SFU grade 2. Logistic regression and time-to-event analysis were performed.

In all, 107 patients were included in the final analysis with the first sonogram performed at a median of 33 days of age (IQR 18-50) and median follow-up age of 2.6 years (IQR 1.2-6.7). The majority were male (n = 85, 79%). The median anterior-posterior renal pelvis diameter (APRPD) was 11.6 mm (IQR 9.2-14.9) and median minimal parenchymal thickness (MPT) was 5.2 mm (IQR 4.0-6.8). Diuresis renography showed a median differential function of 50% (IQR 48-53) in the affected kidney and median T1/2 was 6 min (IQR 4-11). Twenty-nine patients (27%) experienced resolution while 23 additional patients demonstrated improvement to SFU grade 2 (21%). On univariate analyses, MPT, MPT as a ratio to the contralateral measurement (MPTR) and as a ratio to age-based normal values (nMPTR) were associated with any improvement as well as complete resolution while APRPD was associated with resolution alone. On multivariate logistic regression including APRPD and MPT, each millimeter increase in MPT was independently associated with 33% increase in odds of resolution (aOR 1.33, 95%CI 1.05-1.71, p = 0.02) and 26% increase in odds of improvement to at least SFU grade 2 (aOR 1.26, 95%CI 1.02-1.59, p = 0.04). Median time to improvement was 1.8 years and to resolution was 1.6 years. Time-to-event analysis considering competing risk of pyeloplasty demonstrated a significantly higher cumulative incidence of resolution with increasing MPT (sHR 1.41, 95%CI 1.13-1.77, p = 0.003) on initial sonogram. Over time, the minimal parenchymal thickness correlated with the outcome; cases of resolution commonly recovered parenchymal thickness to within one standard deviation of an age-based normal value by one year of age.

Objective measurements of minimal renal parenchymal thickness are independently associated with spontaneous resolution and improvement of isolated SFU grade 3 hydronephrosis prior to age 5 in patients with antenatally diagnosed hydronephrosis.