RETRO Study (RETrograde Renal Access Outcomes)

Inclusion Criteria: * Renal stone or total linear sum of 1.5-3cm cm in maximum dimension (largest diameter in axial or coronal)--- multiple stones should be summed to determine stone size. * Age \>=18 years of age * Gender: both men and women included. * Ethnic background: all ethnicities will be included in the study population and the specific ethnic diversity present in the study population will reflect the geographic distributions of the participating institutions. * Plan for PCNL in the supine position Exclusion Criteria: * Active pregnancy * BMI \>45 * Severe Hydronephrosis - renal pelvis diameter \> 20mm * Flank window \< 4 cm are ineligible for puncture * Previous ipsilateral PCNL * Currently with "useful" nephrostomy tube on ipsilateral side * Uncorrectable coagulopathies * Untreated urinary tract infection * Subjects with significant morbidities such as American Society of Anesthesiologists (ASA) score ≥ 4, severe spinal cord injuries, severe cardiopulmonary insufficiency, uncontrolled diabetes, neurological disorders, bedbound, anticipated life expectancy less than 5 years, or any other comorbidity, that in the opinion of the principal investigator could represent an increased peri-operative risk for the subject; * Ipsilateral partial nephrectomy * History of ipsilateral ureteral reimplantation or ureteral reconstruction; * History of Simple or radical prostatectomy * History of cystectomy * History of calyceal diverticula stone; * History of renal donation or t…