Objective: The mechanism by which the ureter propels urine towards the bladder has a myogenic origin, through peristaltic contractions. This pyeloureteral autorhythmicity is generated by specialized, electrically active cells, the interstitial cells of Cajal, located in the proximal regions of the upper urinary tract. The aim of this study was to describe the exact location and the distribution of interstitial Cajal cells in the human upper urinary tract and to analyze their normal number and morphology. This is a preliminary study, which will allow the study of these cells in different urinary tract pathologies.

Material and Method: Urinary tract fragments were sampled at different levels, from 13 autopsy cases. Cases with clinical evidence of renal disease, and with histological changes in the kidney or in the urinary tract tissue samples, visible in hematoxylin-eosin staining, were excluded. The interstitial Cajal cells were highlighted with anti-CD117 antibody, immunohistochemically.

Results: Cajal cells were indirectly highlighted by the presence of a finely granulated cytoplasm indicating immunoreactivity. These cells were spindle-shaped or stellate, with cytoplasmic extensions at one or both poles of the cell and large oval nucleus. We found that interstitial Cajal cells were located at all upper urinary tract levels, with a higher predominance in the calyces and pyelon. Interstitial Cajal cells were observed mostly between the two layers of the muscularis, but also between the muscle bundles. Most often, these cells were parallel to the muscle fibers.

Conclusion: Our study describes the method of detection of interstitial Cajal cells in normal human urinary tract. These results can be used to analyze the number, morphology and the location of these cells in different congenital pathologies, such as vesicoureteral reflux, pyeloureteral junction obstruction or primary obstructive megaureter.