# Is 3 cm the upper limit of stone size for effective steerable ureteroscopic renal stone evacuation?

## TL;DR

This study evaluates the effectiveness of a new device for removing kidney stones up to 3 cm in size during ureteroscopy.

## Contribution

The study identifies a 3 cm stone size threshold as effective for steerable ureteroscopic renal stone evacuation using the CVAC device.

## Key findings

- A stone-free rate of 63.6% was achieved for stones up to 3 cm.
- Stones smaller than 2 cm had a 95.7% stone-free rate.
- The optimal stone volume threshold was found to be less than 2264.6 mm³ with the CVAC 2.0 device.

## Abstract

The CVAC® Aspiration System is a novel device designed to actively evacuate stone fragments during ureteroscopy. While recent studies have validated its safety, the precise upper limit of stone size for this treatment is undefined. We aimed to determine the ideal size and volume thresholds using CVAC for steerable ureteroscopic renal evacuation (SURE) procedures.

A retrospective, observational study of patients undergoing SURE procedures by a single surgeon between August 2023 and April 2025 was undertaken. Stone size and volume were quantified using preoperative CT imaging. The primary outcome was stone-free status, based on Endourological Society criteria for CT, or <5 mm for ultrasound/X-ray. Receiver Operating Characteristic (ROC) curve analyses were performed to estimate optimal cut-off values for stone size and volume.

Stones in 55 kidneys of 50 patients were removed with this approach. The majority had significant medical co-morbidities (82% ASA Class 3 or 4). The median stone size was 24.0 mm, and the overall stone-free rate (SFR) was 63.6%. For stones smaller than 2 cm, the SFR was 95.7%. ROC analysis identified a stone size of 30.9 mm (AUC 0.895) and a volume of 1501.1 mm³ (AUC 0.834) as predictive cut-offs for clearance. The volume threshold increased to 2264.6 mm³ with utilization of the CVAC 2.0 device. The overall complication rate was 12%, without any high-grade complications.

The SURE procedure with the CVAC device may be effective for treating patients with stones up to 3 cm in size or volumes less than 2200 mm³. Well-designed, randomized prospective studies are needed to confirm these findings.

The online version contains supplementary material available at 10.1007/s00345-026-06310-7.