for people ages 18 years and up (full criteria)
at San Francisco, California
study started
completion around
Principal Investigator
by Thomas Chi, MD
Headshot of Thomas Chi
Thomas Chi



The goal of the study is to determine if ambulatory tubeless PCNL is safe and effective compared to inpatient PCNL with a nephrostomy tube.

Official Title

A Randomized Controlled Trial of Ambulatory Versus Inpatient Percutaneous Nephrolithotomy


One in eight human beings will develop kidney stones during their lifetime. Of these, roughly 20% require surgery. Percutaneous nephrolithotomy (PCNL) is the standard minimally invasive surgical procedure for removal of large kidney stones. In the standard PCNL technique, a drainage tube connecting the kidney to a bag on the outside of the body (nephrostomy tube) is left in place after surgery. Patients are admitted to hospital for one to two days for observation at which time the nephrostomy tube is removed before discharge. The presence of the nephrostomy tube is associated with pain, increased use of opioids, and slower recovery after surgery.

Ambulatory PCNL has been proposed as a way to potentially speed recovery, reduce pain, decrease time in hospital, and decrease cost. Initial studies of ambulatory tubeless PCNL have shown favourable results. However, these studies were performed in a small subset of healthy patients with favourable stones that do not represent the majority of patients who undergo PCNL. In this technique, patients are discharged home the same day as surgery usually with a small drainage tube on the inside of the body called a stent that is removed 1-2 weeks later and no nephrostomy tube (tubeless). The stent itself can be painful and may require a second procedure for removal. There is increasing evidence for the safety of totally tubeless PCNL (in which no nephrostomy tube or ureteric stent is placed) or placement of a stent on a string for a short period of time. Given that current recommendations for stone management in the times of COVID-19 include minimizing use of stents, the investigators believe it is an optimal time to evaluate safety and efficacy of using a minimal stenting technique (either no stent at all or stent on string) in ambulatory PCNL patients.

The goal of the study is to determine if ambulatory tubeless PCNL is safe and effective compared to inpatient PCNL with a nephrostomy tube in a more representative patient population including obese patients, patients with moderate medical comorbidities, and patients with large kidney stones. A secondary aim is to determine if a minimal stent technique (stent on a string for 5 days or less or no stent) is safe and effective as an exit strategy in ambulatory PCNL patients. The study hypothesis is that ambulatory tubeless PCNL will have similar complication and stone free rates as inpatient PCNL with benefits over inpatient PCNL including improved patient quality of life, decreased use of opioid pain medications, shortened hospital admission, faster return to work, and lower cost.


Kidney Calculi, Nephrolithiasis, Calculi, Ambulatory tubeless PCNL, Inpatient PCNL with nephrostomy tube


You can join if…

Open to people ages 18 years and up

  • Scheduled for PCNL who agree to be included in the study
  • Age 18 years or more
  • Absence of renal anatomic abnormalities
  • Patients undergoing bilateral procedures or those with pre-operative indwelling ureteral stents or nephrostomy tubes will be included

You CAN'T join if...


  • Age <18
  • Pregnancy
  • Positive urine culture within 3 weeks
  • Bleeding disorder
  • Presence of renal anatomic abnormalities
  • Solitary kidney
  • Need for admission based on comorbidities determined by anesthesiologist


  • Significant ureteral or pelvicalyceal injury
  • Significant intraoperative hemorrhage


  • Temperature >100.4 Fahrenheit
  • Hemodynamic instability (defined as 2 of 3: heart rate >90 beats per minute, respiratory rate >20 breaths per minute, systolic blood pressure <90mmHg, or drop in systolic blood pressure >40mmHg)
  • Hemoglobin drop of > 3 g/dL compared to pre-operative bloodwork
  • Transfusion of blood products
  • Pneumothorax or hemothorax on chest X ray
  • Uncontrolled nausea, vomiting, or pain


  • UCSF
    San Francisco California 94143 United States

Lead Scientist at UCSF

  • Thomas Chi, MD
    Professor, Urology, School of Medicine. Authored (or co-authored) 138 research publications. Research interests: Nephrolithiasis · Benign Prostatic Hypertrophy (BPH) · Ultrasound · Minimally Invasive Surgery · Laparoscopy


in progress, not accepting new patients
Start Date
Completion Date
University of California, San Francisco
Study Type
Expecting 140 study participants
Last Updated