Research of the factors affecting the surgical intervention and renal function in high grade hydronephrosis (SFU-4) kidneys

Background and Aim: Management of asymptomatic patients with ureteropelvic junction obstruction (UPJO) is challenging. As a result, there is no reliable method to predict whether the function of a kidney with UPJO will remain unaffected or deteriorate with time. Kidneys with large intrarenal pelvis have been reported to be more resistant to obstruction damage than those with small intrarenal pelvis, especially during diuresis. In this study, we aimed to study the relationship between the course of renal function and the renal pelvis anteriorposterior (AP) diameter in cases with UPJO. Material and Method: Twenty-nine patients admitting to the Department of Pediatric Nephrology from January 2000 to December 2019 due to severe unilateral hydronephrosis (SFU grade 3 and 4) and regarded as UPJO by MAG-3 scintigraphy or serial US examinations requiring (28 cases) or not requiring (1 case) pyeloplasty were enrolled in the study. Demographic data, height and height percentile values, age at presentation (antenatal or postnatal determination), ultrasonographic and radionuclide imaging data, plasma creatinine and glomerular filtration rate values were noted. Cases divided into different renal pelvis AP diameter groups were compared in terms of renal parenchyma thickness, kidney length, kidney echogenicity and differential kidney functions. Results: Out of 29 patients, 7 (24%) were female and 22 (76%) were male. Thirteen patients (45%) were detected antenatally, and 16 patients (55%) were diagnosed postnatally. Median age at presentation was 40.2 months. UPJO was located in the right kidney in 7 patients (24%) and the left kidney in 22 patients (76%). The most common reason for presentation was the detection of hydronephrosis in antenatal screening. In postnatal cases, the most common reason for presentation was flank pain. All but one patient required pyeloplasty. When all patients divided into two groups as renal pelvis AP diameter ≤20 mm and ≥21 mm, there was no difference between the groups with respect to parenchymal thickness and differential functions (percentile of MAG-3 uptake) of hydronephrotic kidneys. Both hydronephrotic and intact kidney lengths were significantly higher in the group with AP diameter ≥21 mm. 4 Patients with only SFU-4 hydronephrosis were grouped differently with respect to age as follows: Patients <1 year of age (n=10) were grouped as renal pelvis AP diameter ≤29 mm and ≥30 mm, and patients >1 year of age (n=7) as AP diameter ≤39 mm and ≥40 mm. Parenchymal thickness and differential functions of hydronephrotic kidneys were not different between the groups in both age groups. Hydronephrotic kidney length in patients <1 year of age was significantly higher in those with AP diameter ≥30 mm. AP diameter was not correlated with parenchymal thickness and differential function in the hydronephrotic kidneys in all children with SFU-4 hydronephrosis. Conclusion: In this study, we could not find any relationship between the renal pelvis AP diameter and renal parenchymal thickness and differential function in high grade hydronephrosis. This may be due to inclusion of only the patients with UPJO requiring pyeloplasty. Thus, there is a need for further studies including the patients with antenatal diagnosis of high grade hydronephrosis who do not need pyeloplasty during follow up.