Abstract

Background: Ureteropelvic Junction Stenosis (UPJS) is one of the main causes of hydronephrosis caused by Ureteropelvic Junction Obstruction (UPJO) , which can damage renal function in severe cases.We want to explore more possible etiologies of UPJO by means of compare the pathological features of different anatomical sites in the specimens obtained from children with UPJO caused by UPJS, in particular, differences in the number and distribution of Interstitial Cells of Cajal (ICCs)，muscle and collagen.

Methods: A total of 34 surgical specimens were obtained, centered on the stenotic lesion segment as UPJ segment. A 1.5 cm range of renal pelvis tissue was taken along its upper edge and used as a normal control. A 1.5 cm area of tissue was taken from the ureteral along the lower edge of the UPJ segment for the ureteral stricture segment. Hematoxylin-eosin staining, Masson staining, and immunohistochemistry were used to observe the tissue arrangement of different parts, the number and distribution of ICCs, the muscle to collagen ratio (MC ratio). Two different physicians checked the number of cells in 9 fields of view under the microscope and calculated the mean value and the distribution of muscle and collagen was analysed using the online software ImageJ. The final results were analysed using SPSSPRO by multiple samples Friedman test and paired test.

Results: The highest number of ICCs was found in the renal pelvic segment, which was significantly different from both the UPJ segment and the ureteral stenosis segment. There was no statistically significant difference between the UPJ segment and the ureteral stenosis segment. Collagen fiber hyperplasia was most pronounced in the UPJ segment, and the muscle-to-collagen fiber ratio and collagen fiber volume differed in all three different sites.

Conclusion: In UPJO due to UPJ stenosis, the number of ICCs in the UPJ segment is reduced or even absent compared to normal tissue, but there is no significant difference with the ureteral stenosis segment. 2. When ureteral buds develop from the middle to the ends, the lesion is triggered by one of the upper ureteral segments and terminates at the ureteropelvic junction, not starting at the ureteropelvic junction.

Keywords: Hydronephrosis; Ureteropelvic junction stricture; Histopathology; ICCs; Collagen fibrosiS