The physiology of the upper urinary tract in endourological times - a narrative review.

OBJECTIVE: To synthesise current knowledge of upper urinary tract (UUT) physiology in the context of contemporary endourology, with particular emphasis on the interacting biological stressors associated with endourological intervention and the tissue responses they provoke. PATIENTS AND METHODS: A narrative review of the literature was conducted using PubMed/MEDLINE. Relevant experimental, translational and clinical studies examining UUT physiology, tissue injury and biological responses to ureteroscopy, percutaneous nephrolithotomy, irrigation and intrarenal pressure, laser lithotripsy, suction-assisted technologies, intracavitary therapies and ureteral stents were considered. RESULTS: The UUT is a biologically active organ whose function depends on coordinated peristalsis, urothelial barrier integrity, pressure regulation and preserved tissue perfusion. Contemporary endourological procedures expose the UUT to interacting mechanical, pressure-related, parenchymal, thermal and chemical stressors that may influence urothelial permeability, intrarenal backflow, inflammation, tissue repair and fibrosis. Tissue tolerance appears to vary considerably between individuals and may be influenced by factors including hydronephrosis, collecting-system compliance and papillary morphology. Despite these biological effects, current outcome assessment remains predominantly focused on technical success, while physiological and biological safety endpoints remain poorly defined. CONCLUSION: Future advances in endourology should integrate physiological and biological outcome measures alongside traditional surgical metrics. Improved understanding of UUT physiology and tissue responses may help define evidence-based thresholds and support endourological treatment that is both technically effective and biologically safe.