Introduction & Objectives
Miniaturization of ureteroscopy materials is intended to decrease tissue damage, thus decreasing morbidity in the treatment of ureteral stones. However, the gross and microscopic effects on tissue have not been adequately compared. The purpose of this study was to compare the gross and microscopic effects of micro-ureteroscopy (m-URS) and conventional ureteroscopy (URS) on the urinary tract.
Material & Methods
Approval was obtained from the ethics committee for animal experimentation. 14 sows of the Large White race weighing 30-35 kg were subjected to the procedure because of their suitability for endourology research. URS was performed in one of the ureters with an 8/9.8 Fr. ureteroscope, while a 4.85 Fr. m-URS sheath was used in the contralateral ureter. In both cases, 21 cm of the instrument were inserted. Operative time was 45 and 60 min for URS and m-URS respectively according to the mean duration in human patients in previous studies. For gross assessment of tissue damage, at the end of each intervention ureteral damage was classified using the Post-Ureteroscopic Lesion Scale (PULS). Damage caused to the ureteral meatus was also blindly assessed. For microscopic assessment, once both procedures were completed, a tissue ischemia marker, pimonidazole, was injected, humane euthanasia was performed, and samples were taken from each of the ureters at both distal and proximal levels. Hematoxylin-eosin staining and immunohistochemistry for detection of tissue hypoxia were conducted. For contrasting effect size between the two procedures Cliff's delta was employed. For detecting associations between the procedures and the damage caused the Wilcoxon rank sign test was applied.
Regarding the blinded macroscopic assessment of ureteral damage no differences between the baseline and final conditions of the ureteral orifice were observed with m-URS. In contrast, substantial and significant differences were recorded on using URS (C = 0.8 ([95%CI] 0.5-1). The lesions as scored by the PULS showed no statistical differences between the two groups. Microscopic assessment after staining with hematoxylin-eosin revealed greater diffuse epithelial desquamation in in the URS group (p < 0.05). Pimonidazole staining revealed greater hypoxia in the epithelial cells than in the rest of the ureteral layers.
m-URS is a procedure that decreases damage to the ureteral meatus as compared to conventional ureteroscopy with an 8/9.8 Fr. ureteroscope in animal models. m-URS causes less urothelial damage than conventional ureteroscopy. m-URS and URS cause transient cell hypoxia events at ureteral level.