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 transplant;
* Any other previous pelvic surgical treatment that could put the subject at greater procedural complication risk or technical difficulty;
* Ureteral ipsilateral stricture, untreated;
* Ureteral stricture, untreated (not to include "tight" ureter);
* Any other bladder, ureteral or kidney congenital genitourinary abnormalities (e.g. Horseshoe kidney, ipsilateral duplicated or partially duplicated collecting system, ipsilateral ectopic kidney, cross-fused ectopia, bifid renal pelvis with no horizontally directed calyces, solitary kidney, etc.) preventing the ability to direct a puncture laterally or render the subject stone free;
* Have participated in any other clinical trial within the last 3 months, and/or plans to participate in any other investigational or invasive clinical trial during this study;
* If female, breast-feeding, or if childbearing age, is not using contraception between screening and 90 days post-op;
* Subject has current or recent history of substance abuse (e.g. recreational drugs, narcotics, or alcohol) requiring intervention;
* Is a prisoner or ward of the state;
* Is unable to meet the treatment and follow up protocol requirements.