and Purpose: The study compared characteristics and outcomes in patients with solitary and bilateral kidneys who were treated with percutaneous nephrolithotomy (PCNL) in the Clinical Research Office of the Endourological Society (CROES) PCNL Global Study. Patients and Methods: Data from consecutively treated patients from 96 centers worldwide were collated after a 1-year period. The following variables in patients undergoing PCNL with solitary or bilateral kidneys were compared: Prevalence,

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... ent characteristics, intraoperative differences and outcomes, including bleeding and transfusion rates, renal function, and stone-free rates. Results: Data from 5803 patients were collated; 189 (3.3%) with solitary and 5556 (96.7%) with bilateral kidneys. Patient characteristics were well matched generally with the exception of cardiovascular disease and American Society of Anesthesiologists (ASA) risk scores, which were significantly greater in patients with solitary than with bilateral kidneys (P < 0.0001 and P = 0.004, respectively). Patients with solitary kidneys had also undergone significantly more procedures to remove calculi before this survey than bilateral patients (P = 00.049 -< 0.0001). Levels of renal impairment were significantly greater (P < 0.0001) and stone-free rates were significantly lower (P = 0.001) post-PCNL in solitary than bilateral kidney patients. Although bleeding rates were the same in both groups, transfusion rates were significantly greater in solitary kidney patients (P = 0.014). Conclusions: Patients with a solitary kidney had a higher cardiovascular risk and ASA score. Outcomes related to morbidity and stone-free rate were less favorable for solitary kidneys.