Size is Not Everything That Matters: Preoperative CT Predictors of Stone Free After RIRS.

Area of Science:

• Urology
• Medical Imaging
• Nephrology

Background:

• Retrograde intrarenal surgery (RIRS) is a common treatment for kidney stones.
• Identifying predictors of residual stone fragments post-RIRS is crucial for optimizing patient outcomes.
• Previous studies have not fully elucidated CT-based predictors for residual fragments in primary RIRS cases.

Purpose of the Study:

• To identify computed tomography (CT) predictors of residual stone fragments after retrograde intrarenal surgery (RIRS).
• To evaluate the association between preoperative CT parameters and stone-free status in patients undergoing RIRS for kidney stones up to 20 mm.
• To specifically assess the infundibulopelvic angle (IPA) as a predictor of residual fragments.

Main Methods:

• Prospective evaluation of pre- and postoperative CT scans in 92 adult patients undergoing RIRS for kidney stones < 20 mm.
• Analysis of stone size, volume, number, density, and location (IPA) on preoperative CT.
• Assessment of residual stone fragments on 90-day postoperative CT scans.

Main Results:

• 74.8% of patients were stone-free, 8.7% had 0-2 mm fragments, and 16.5% had > 2 mm residual fragments.
• Logistic regression identified a steep infundibulopelvic angle (IPA) as a significant predictor of residual fragments (P = .012).
• Receiver Operating Characteristic (ROC) curve analysis indicated that an IPA < 41° was associated with a higher likelihood of residual fragments.

Conclusions:

• An infundibulopelvic angle (IPA) less than 41° on preoperative CT is a significant predictor of residual stone fragments after RIRS.
• This CT-derived metric can help anticipate treatment success and guide surgical planning for kidney stones up to 20 mm.
• Understanding IPA's role can improve patient selection and management strategies for RIRS.