Schwentner C et al. - Several cytokines are differentially expressed in primary refluxing ureters, indicating an ongoing tissue remodeling process in the ureterovesical junction region. Additionally, the smooth muscle coat is widely lacking, while extracellular matrix proteins typical for tissue shrinkage and reorganization are over expressed. These alterations are likely to contribute to the malfunctioning active ureteral valve mechanism in primary vesicoureteral reflux.