Assessing inter-rater reliability of objective renal sonographic measurements for identification of clinically significant ureteropelvic junction obstruction.

INTRODUCTION

Anterior posterior renal pelvis diameter (APRPD) and minimal parenchymal thickness ratio (MPTR) on renal ultrasonography (RUS) have been identified as measures to help risk stratify patients with hydronephrosis for adverse findings on diuretic renography (DR). Widespread adoption of these measures requires reliable assessment by providers to ensure accurate risk stratification.

OBJECTIVE

To assess the inter-rater reliability between pediatric radiologists measuring APRPD and minimum parenchymal thickness (MPT) on RUS in patients who also underwent DR for evaluation of hydronephrosis. A secondary objective was to assess whether individual radiologist measurements for APRPD and MPT differed based on Society for Fetal Urology (SFU) grade, prolonged drainage time on DR, or decreased differential renal function (DRF) (<40 %).

STUDY

DESIGN

We conducted a retrospective cohort study of children who underwent DR within 120 days of RUS for the evaluation of hydronephrosis. We included patients with isolated unilateral SFU grade 3 and 4 hydronephrosis. Non-parametric tests were used to compare cohorts with and without prolonged drainage time (t1/2 > 40 min) or decreased DRF (<40 %) on DR. Covariables included SFU grade, laterality, sex, antenatal diagnosis of hydronephrosis, and time interval between studies. Intraclass-correlation coefficient (ICC) for absolute agreement was calculated for APRPD and MPT.

RESULTS

112 patients met inclusion criteria. Studies occurred between October 2011 and January 2024. Median age at the time of DR was 1.6 years and the median interval between RUS and DR was 30 days. The majority of patients were male (71 %), had antenatal detection of hydronephrosis (85 %), and had left sided hydronephrosis (63 %). Rates of SFU grade 3 and 4 hydronephrosis were similar (45 % and 55 %, respectively). Patients with decreased DRF or prolonged drainage time were more likely to have SFU grade 4 hydronephrosis. For APRPD and MPT, ICC values were good to excellent, with ICC of 0.88 (95 % CI 0.82-0.92) and 0.86 (95 % CI 0.77-0.91) respectively, and remained so on subgroup analysis by SFU grade. APRPD and MPT measurements were significantly different in patients with SFU grade 3 vs 4 hydronephrosis for both radiologists.

DISCUSSION AND

CONCLUSION

APRPD and MPT were reliably measured by radiologists with good to excellent ICC. These have the potential to serve as objective measures to assess risk of abnormal findings on DR. Future prospective studies to assess their utility in risk stratifying patients with hydronephrosis and suspected UPJ obstruction are warranted.