Comparison of two classifications of the calyx-pelvic system dilation UTD and SFU in predicting surgical treatment of uropathies in children

INTRODUCTION : Accurate criteria of norm and pathology, as well as assessment of the degree of risk of adverse outcomes, are necessary to determine the managing of children with dilated calyx-pelvic system (CPS). The new classification of urinary tract dilation (UTD 2014) was created to standardize the primary ultrasound examination (US) and further management of such patients, but it needs validation in clinical practice. OBJECTIVE : The aim was to compare two classifications of the dilation of the CPS (UTD and SFU) in predicting the need for surgical treatment of uropathies in children. MATERIALS AND METHODS : The retrospective study included 152 children with dilated CPS due to various uropathies. The results of US of the urinary tract in accordance with the SFU and UTD classifications and the analysis of the frequency and time of surgical interventions for the correction of uropathies were evaluated. Statistics : The data are presented as median, minimum and maximum, interquartile range. The Kraskal-Wallis method and the Mann–Whitney U-test were used to compare the groups. Surgery-free survival curves were constructed using the Kaplan-Meyer method. The diagnostic significance of the prognostic model was assessed by the ROC curve method. The differences were considered significant at p < 0,05. RESULTS : The median age of patients at the time of the first US was 4 days, the median follow–up was 10 months. Surgical treatment was performed in 27 (18%) patients: 0/8/35/60% of patients with SFU categories I/II/III/IV; 0/2/31/60% of patients with UTD categories 0/I/II/III, respectively. Both classifications made it possible to stratify the risk of surgical intervention with high accuracy (AUC 0,836 and 0,873 for SFU and UTD, respectively). Surgery-free survival curves of patients differed depending on the SFU category, however, the differences between SFU I and II, as well as SFU III and IV were not significant; the curves of UTD 0 and I practically coincided, while the differences between the other UTD categories were statistically significant (p≤0,001). DISCUSSION : The main differences between the UTD and the SFU classifications is that, besides to describing the CPS and renal parenchyma, US characteristics of the ureters and bladder were added, and a lower threshold value of the anterior-posterior pelvis size was proposed — its isolated expansion to 10 mm is considered a variant of the norm (according to SFU — 5–7 mm). The data of our study demonstrated that the new standards for the pelvis size do not lead to an underestimation of the risk of uropathies in children, and additional US signs make it possible to stratify the risks not only for patients with isolated hydronephrosis, such as SFU, but also for patients with other uropathies (vesicoureteral reflux, obstruction of the ureterovesical junction, ureterocele). CONCLUSIONS : The UTD has high accuracy in predicting the need for surgical intervention in children with dilated CPS and is not inferior to the SFU in this. Isolated expansion of the pelvis to 10 mm and central calyces does not increase the likelihood of surgical treatment and can be regarded as a variant of the norm.