Diagnostic accuracy of Onen’s Alternative Grading System combined with Doppler evaluation of ureteral jets as an alternative in the diagnosis of obstructive hydronephrosis in children

Abstract

IntroductionUreteropelvic junction obstruction (UPJO) is a common congenital anomaly leading to varying degrees of hydronephrosis (HN), ranging from no apparent effect on the renal function to atrophy. Evaluation of these children is based on Diuretic Renal Scintigraphy (DRS) and Ultrasonography (US). Recent studies have suggested that new parameters of conventional and color Doppler ultrasonography (CDUS) may be useful in discriminating which kidneys are obstructed. The present study aims to assess the diagnostic accuracy of such parameters in the diagnosis of obstruction in children with UPJO.MethodsWe evaluated 44 patients (33 boys) with a mean age of 6.53 ± 4.39 years diagnosed with unilateral high-grade hydronephrosis (SFU grades 3 and 4). All underwent DRS and index tests (conventional US and CDUS to evaluate ureteral jets frequency) within a maximum interval of two weeks. Hydronephrotic units were reclassified according to the alternative grading system (AGS) proposed by Onen et al. Obstruction in the DRS was defined as a differential renal function <40% on the affected side and/or features indicating poor drainage function like T1/2 >20 minutes after the administration of furosemide, and a plateau or ascending pattern of the excretion curve.ResultsNineteen hydronephrotic units (43.1%) were obstructed. Some degree of cortical atrophy—grades 3 (segmental) or 4 (diffuse)—was present in those obstructed units. AGS grades had 100% sensitivity, 76% of specificity and 86.4% of accuracy. The absence of ureteral jets had a sensitivity of 73.68%, a specificity of 100% with an accuracy of 88.6%. When we analyzed the two aspects together and considered obstructed the renal units classified as AGS grade 3 or 4 with no jets, sensitivity increased to 78.9%, accuracy to 92%, remaining with a maximum specificity of 100%. These features combined would allow us to avoid performing DRS in 61% of our patients, leaving more invasive tests to inconclusive cases.ConclusionsAlthough DRS remains the mainstay to distinguishing obstructive from non-obstructive kidneys, grade of hydronephrosis and frequency of ureteral jets, independently or in combination may be a reliable alternative in the mostly cases.This alternative approach has high accuracy, it is less invasive, easily reproducible and may play a role in the diagnosis of obstruction in pediatric population.

Grading of Hydronephrosis: An Ongoing Challenge

“…Considering parenchymal loss, SFU and UTD are the same, differing from the Onen grading system that stratifies it in cortical and medullary loss, which was found clearly more precise (1,21). Recent studies have shown that patients with Onen-3 had better renal function than Onen-4, proving that this difference is relevant to choosing this grading system for children (1,4,5,11,21). Bienias and Sikora have shown that 21/25 (84%) children with Onen grades 3 and 4 developed obstructive nephropathy with impaired relative function from 15 to 35% (44).…”

“…Onen grading system has a sensitivity of 100%, specificity of 76%, and accuracy of 86.4% (21). In a recent study, all units that had Onen-1 and 2 were not obstructed and had renal function > 40% while Onen grade-4 had 100% specificity, meaning that it consistently predicts kidney damage due to obstruction when present (1,21). Therefore, renal scan is required for only Onen-3 patients; thus, renal scan could be avoided in more than two-thirds of cases (1,21).…”

“…The upgraded Onen grading system not only uses the quality of the renal parenchyma but also takes into account both affected and contralateral kidney size including longitudinal length and atrophy (1). Considering parenchymal loss, SFU and UTD are the same, differing from the Onen grading system that stratifies it in cortical and medullary loss, which was found clearly more precise (1,21). Recent studies have shown that patients with Onen-3 had better renal function than Onen-4, proving that this difference is relevant to choosing this grading system for children (1,4,5,11,21).…”

“…It has previously been shown that the Onen grading system determines the severity of UPJHN better and make follow-up more practical compared to SFU and UTD (1,11). It is reliable and easily reproducible and plays a significant role in the diagnosis of obstruction in children (1,21). Therefore, the use and popularity of this grading system are increasing around the world (20)(21)(22)45).…”

Diuretic Enhanced Ultrasonography in the Diagnosis of Pyeloureteral Obstruction

“…Postnatal ultrasound cut-off values for renal obstruction on DRS have been suggested to be 15–20 mm AD [27]. Onen’s alternative grading system, of grades 3 or 4 with no jets on a Doppler scan, increased sensitivity to 78.9% and accuracy to 92% in diagnosing obstruction [28]. Prospective study has shown that the parenchyma/hydronephrosis area ratio has been more accurate in predicting obstruction in comparison to SFU grade and AD, but requires specific software for calculations [29].…”