for people ages 18 years and up (full criteria)
Healthy Volunteers
healthy people welcome
at San Francisco, California
study started
completion around
Principal Investigator
by Thomas Chi, M.D.
Headshot of Thomas Chi
Thomas Chi



The purpose of this study is to assess the accuracy of ultrasound and traditional fluoroscopy to find the residual fragments before retrograde intrarenal surgery is complete. This would ultimately limit the need for radiation exposure and improve the quality of clinical care given to patients and healthcare teams.

Official Title

Diagnostic Accuracy of Ultrasound Versus Fluoroscopy for Detecting Residual Fragments During Retrograde Intrarenal Surgery: a Randomized Controlled Trial


Ultrasound is currently gaining popularity as an alternative imaging modality for the diagnosis and treatment of urolithiasis. However, the benefit of ultrasound on the diagnostic accuracy of detecting residual fragments during retrograde intrarenal surgery (RIRS) has never been evaluated in a randomized study. Its use would reduce radiation exposure for patients and care team members as well as improve stone free clearance rates for surgery. Therefore, The investigators plan to conduct a randomized trial to assess the diagnostic accuracy of ultrasound and fluoroscopy in conjunction with endoscopic examination for detecting residual stone fragments during retrograde intrarenal surgery. After admission, approximately 172 subjects will be randomized in a 1:1 ratio to receive ultrasound or fluoroscopy before completing RIRS. Subsequently, four weeks after the operation, the investigators will compare with routine low-dose non-contrast computed tomography as a gold standard for detecting residual fragments. If ultrasound is more accurate than fluoroscopy in detecting residual fragments, the investigators will encourage this approach as it can reduce radiation exposure for patients and healthcare professionals.


Stone, Kidney, Ultrasound Therapy; Complications, residual stone, ureteroscopy, ultrasound, diagnostic accuracy, Kidney Calculi, Nephrolithiasis, Fluoroscopy


You can join if…

Open to people ages 18 years and up

  • Patients over the age of 18.
  • Consecutive patients with a diagnosis of renal stone or ureteral stone with a plan to undergoing RIRS for stone removal.

You CAN'T join if...

  • Patients who decline informed consent.
  • Pregnancy
  • Kidney transplantation
  • Ectopic kidney
  • Patients undergoing concurrent bilateral stone removal surgery.
  • Patients whose pain cannot be controlled when presenting at the Emergency Department.


  • UCSF accepting new patients
    San Francisco California 94143 United States

Lead Scientist at UCSF

  • Thomas Chi, M.D.
    Professor, Urology, School of Medicine. Authored (or co-authored) 139 research publications. Research interests: Nephrolithiasis · Benign Prostatic Hypertrophy (BPH) · Ultrasound · Minimally Invasive Surgery · Laparoscopy


accepting new patients
Start Date
Completion Date
University of California, San Francisco
Study Type
Expecting 172 study participants
Last Updated