Telocyte and Cajal cell distribution in renal pelvis, ureteropelvic junction (UPJ), and proximal ureter in normal upper urinary tract and UPJ obstruction: reappraisal of the aetiology of UPJ obstruction

Background: Telocytes and Cajal cells have been described in human urinary tract and reproductive system in women and men. Telocytes and Cajal cells have been differentiated from other interstitial cells and were described to be an element in smooth muscle conductivity. Previous studies examined the ureteropelvic junction (UPJ) segment in patients with UPJ obstruction (UPJO) and attributed the aetiology of UPJO to the low density or absence Cajal cells and telocytes. The present work aimed at the demonstration of the presence and the density of telocytes and Cajal cells in the upper urinary tract (UUT) in cases with normal UUT and UPJO. It included UPJ segment, renal pelvis, and proximal ureter. The morphological pattern of distribution of collagen in relation to smooth muscle was investigated in normal and obstructed UUT. Materials and methods: The study was carried out on 12 surgical specimens, 5 of them represented the normal UUT and underwent nephrectomy for oncological reasons. Seven patients underwent dismembered pyeloplasty for UPJO. Surgical specimens included renal pelvis, UPJ segment, and proximal ureter. They were subjected to standard haematoxylin and eosin stain, Gomori's trichrome stain, immunohistochemistry with c-kit, and transmission electron microscopy. Results: Telocytes and Cajal cells were demonstrated in the muscular layer of both normal UUT and UPJO with high density in the proximal ureter in normal UUT as well as in UPJO. The UPJ segment in normal UUT had moderate density of Cajal cells and telocytes while in UPJO the cells were scanty or absent. Renal pelvis in normal UUT showed excess density of cells while obstructed renal pelvis showed scanty Cajal cells and telocytes. Ultrastructural study showed the presence of Cajal cells, telocytes, stem cells, fibroblasts, smooth muscle cells, and collagen in different densities and distribution in normal and obstructed UUT. Conclusions: Examination of the UPJ segment of UPJO revealed that Cajal cells and telocytes were scanty or absent, collagen to muscle ratio was high. The low density of Cajal cells and telocytes in the renal pelvis of the obstructed UUT, compared to the normal, points out to the role of the renal pelvis in the pathogenesis of UPJO.