The relationship between calcium-based calculi and Randall plaques is well documented, but the role these plaques play in the early process of urinary stone formation remains unknown. The vascular hypothesis of Randall plaque formation has been proposed, and recent works support this concept. The renal papilla's vascular environment is subject to relative hypoxia, hyperosmolar surroundings, and turbulent blood flow. These factors together create an environment prone to vascular injury and may potentiate Randall plaque precipitation. Recent data support the similarity between the vascular calcification process itself and urinary stone formation. Furthermore, epidemiological studies have suggested an association between urinary stones, adverse cardiovascular events, and vascular calcification risk factors. The concept that an initial vascular insult precipitates a Randall plaque and subsequent urolithiasis is compelling and represents an area in need of continued research. This may lead to future novel treatment approaches to urolithiasis.

Maintenance of flexible ureteroscopes can involve high costs and administrative burden. Instrument fragility necessitates eventual repair, rendering scopes inaccessible during refurbishment. We conducted a multi-institutional prospective cohort study to identify perioperative factors influencing flexible ureteroscope durability. Patients undergoing flexible ureteroscopy (URS) at six United States endourology centers were enrolled between August 2014 and June 2015. Surgeon self-reported concern and satisfaction with scope performance as well as upward and downward angles of deflection for each scope tip were measured before and after each procedure. The need for scope repair was determined by the operating surgeon at the time of the procedure and recorded. 424 URS cases using 74 flexible ureteroscopes were identified. Scope repair was required in 28 cases (6.6%) involving 26 scopes (35.1%). Upon univariate analysis, shorter patient height, absence of guidewire use, presence of a ureteral access sheath (UAS), longer procedure time, larger stone size, lithotrite type, surgeon training level, and self-reported concern were associated with scope repair. Upon multivariate analysis, UAS use (OR = 2.53, p = 0.005) and degree loss of scope upward flexion during a case (OR = 1.02, p = 0.03) increased the odds of a scope needing repair while the use of safety guidewire decreased the odds of a scope repair (OR = 0.50, p = 0.045). Lithotrite use and surgeon concern were associated with degree loss of scope upward flexion. The use of a UAS, absence of a safety guidewire, and the loss of upward ureteroscope flexion should be considered when evaluating means of optimizing reusable ureteroscope durability.