Ultrasonographic renal parenchymal volume measurement in pediatric patients with unilateral hydronephrosis

Aim: Ureteropelvic junction stenosis (UPJO) refers to the obstruction of urine flow from the renal pelvis to the proximal ureter. In such a situation, urine collected in the renal pelvis causes an increase in pressure and stretching of the pelvic wall. The renal pelvis can adapt to the current situation for some time, but when it loses its viscoelasticity, the increased intrapelvic pressure causes irreversible kidney damage. There are many studies and articles published on the follow-up of the disease, especially on the timing of surgical treatment, but unfortunately there is no consensus on this issue. Undoubtedly, what is desired in determining the indication for surgery is that it is cheap, accessible and does not work with ionizing radiation. Therefore, a different parameter is needed for the follow-up and surgical decision of UPJO. Parenchymal kidney volume is thought to be an important parameter in recent studies. In our study, we aimed to measure renal parenchymal volume using USG in patients with unilateral UPJO. Material and Methods: A total of 24 patients between the ages of 0-18 years with unilateral hydronephrosis diagnosed as UPJO who were admitted to Manisa Celal Bayar University Pediatric Surgery Clinic between March 2023 and September 2023 were included in our study. Transverse sections of the kidneys of the patients included in the study were video-recorded by USG (Canon Aplio A-Tokyo, Japan) with probe movement from inferior to superior kidney, then 5 equally spaced cross-sectional images (segmentation) were extracted from these images. These images were merged using Adobe 360 program and parenchymal volumes were measured. The measured parenchymal volumes were divided into 2 groups as normal kidney and kidney with UPJO and these groups were compared in terms of hydronephrosis, AP diameter and parenchymal thickness parameters. Shapiro-Wilk correlation test was used to evaluate whether the numerical variables were normally distributed. Differences between groups were analyzed with the non-parametric Wilcoxon signed analysis test. A value of P<0.05 was considered significant. Results: The parenchymal volumes of the 24 patients who participated in the study showed a mean parenchymal volume of 49.452 mm3 ± 23.287 mm3 in kidneys with UPKD, while the mean parenchymal volume in normal kidneys was 57.979 mm3 ± 27108 mm3. When the parenchymal volumes of normal kidneys were compared with the parenchymal volumes of kidneys with HN and compared with the HN grades, no significant difference was found between grade 2 and grade 3 HN (p>0.05). When grade 3 was compared with grade 4 HN, no significant difference was observed in this group (p>0.05). Finally, when a comparison was made between grade 2 and grade 4 HN, a significant difference was observed between both groups (p<0.05). Conclusion: Our study showed that parenchymal volume can be measured with USG and we think that performing these measurements in more cases in future studies may be a reliable parameter in surgical decision making.