Low-dose CT and ultrasound are key to safer stone treatment

In this video, Dinesh Singh, MD, associate professor of urology, Endourology Chief, Urology; director of Laparoscopy & Endourology, Urology; and director of the Endourology Fellowship, Urology at Yale School of Medicine in New Haven, Connecticut, outlines a multilayered approach to minimizing radiation exposure for patients with kidney stones across diagnosis and treatment.

He emphasizes that radiation reduction begins at the diagnostic stage, favoring low-dose CT scans over standard-dose imaging. For shock wave lithotripsy, he relies heavily on ultrasound guidance, whereas patients undergoing percutaneous nephrolithotomy (PCNL)—who typically require preoperative CT — still receive low-dose protocols. Post-PCNL imaging is a particular focus: Singh advocates for low-dose CT to confirm stone-free status and guide decisions about additional intervention, a practice his institution has implemented for nearly a decade.

On ultrasound vs fluoroscopy, Singh acknowledges ultrasound's cost and accessibility advantages but notes its limitations in visualizing the ureter. He references a New England Journal of Medicine study showing no increased adverse outcomes when ultrasound was used instead of CT for suspected kidney stones.¹ He also highlights a Yale-developed clinical prediction tool—the STONE score, published in BMJ—that identified ureteral stones in roughly 88% of high-probability patients, supporting a strategy of using ultrasound first in stable, low-risk cases and reserving CT for those with persistent symptoms.²

To reduce intraoperative radiation exposure, Singh identifies several underutilized fluoroscopy techniques. These include low-dose fluoroscopy settings, pulsed radiation modes, and collimation—narrowing the imaging field to only the relevant anatomy—which reduces exposure for everyone in the operating room. He also advises removing metal objects from the radiation field to minimize scatter and positioning the image sensor close to the patient. Although individual case exposure may seem modest, Singh stresses that cumulative lifetime radiation for clinicians performing fluoroscopy is significant, making these practices essential for both patient and provider safety.

REFERENCES

1. Smith-Bindman R, Aubin C, Bailitz J, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl J Med. 2014;371(12):1100-1110. doi:10.1056/NEJMoa1404446

2. Moore CL, Bomann S, Daniels B, et al. Derivation and validation of a clinical prediction rule for uncomplicated ureteral stone—the STONE score: retrospective and prospective observational cohort studies. BMJ. 2014:348:g2191. doi:10.1136/bmj.g2191