Ureteroscopy remains the most commonly performed surgical procedure for kidney stones. While flexible ureteroscopy has become increasingly effective, fragment and dust clearance and control of intrarenal pressure remain ongoing challenges. Over the last decade, suction and aspiration technologies have been introduced to address these issues. Two such strategies, direct in-scope suction (DISS) and the CVAC Aspiration System (Calyxo, Inc.), represent distinct approaches with unique strengths and limitations.

DISS

DISS integrates suction directly through the working channel of the ureteroscope. The earliest versions relied on manual stopcocks and adapters, but newer platforms such as the Pusen (Pusen Medical; Figure 1) or Vathin (Vathin Medical) digital disposable ureteroscopes incorporate built-in suction channels. Clinical studies have demonstrated encouraging results. Nedbal et al reported an initial stone-free rate of 84% using a 7.5F Pusen DISS ureteroscope across 57 cases, with 94.7% of surgeons rating suction as helpful and all indicating willingness to use it again.¹ Geavlete et al subsequently showed higher stone-free rates when combining DISS with suction-assisted access sheaths compared with standard ureteroscopy (97% vs 83%).²

The advantages of DISS include its smaller scope size (7.5F-9.2F), lower cost, and ease of integration into existing workflows. However, the limitations are significant. Suction must alternate with irrigation, which reduces efficiency, and fragment clearance is generally restricted to particles < 0.25 to 0.5 mm. Larger fragments still may require basket retrieval, and excessive suction can temporarily collapse calyces, occasionally leading to transient mucosal bleeding from calyceal or ureteral wall collapse. Nonetheless, clinical complications remain rare.³

CVAC 2.0 Aspiration Scope

The CVAC platform was developed to overcome the inherent limitations of traditional suction-through-the-scope approaches (Figures 2 and 3). Its second-generation design integrates dual irrigation and aspiration channels into an 11.9F single-use digital ureteroscope, allowing continuous flow and the ability to mobilize and evacuate fragments up to 2 mm without interrupting visualization. The system maintains active or passive suction depending on the trigger position, and its large working channel also accommodates a stabilization catheter for the laser during lithotripsy.

New clinical data highlight how these design features translate into real-world performance. In the first multicenter in vivo evaluation of CVAC 2.0, conducted across 2 tertiary centers, surgeons treated patients with substantial stone burdens, most exceeding 2 cm or 800 mm³ in volume. Despite this challenging population, the device achieved a median stone-volume reduction of > 98%, and residual volume remained low even as preoperative stone size increased. This is a notable departure from conventional ureteroscopy, where efficiency typically declines as stone burden grows. Importantly, the safety profile was favorable: intraoperative complications were uncommon, postoperative infections were infrequent, and no cases of sepsis were observed. Intermittent clogging of the suction channel did occur, but it was easily corrected with simple maneuvers.⁴

Despite these advantages, the CVAC system has some limitations. The larger scope typically requires a 12F/14F access sheath, which may limit usability in non–pre-stented patients. In addition, because of the scope size, there is some surgeon thumb fatigue with prolonged flexion, particularly noticeable during larger stone burdens in the lower pole. The lack of a built-in pressure-relief system means that unrecognized channel obstruction can raise intrarenal pressures, which raises concern for rare but serious complications such as infection or fornix rupture. Thus, while synchronous suction and irrigation improve stone clearance, attention to device limitations and patient safety are essential.

Comparative Considerations

DISS offers accessibility, smaller-caliber scopes, and cost-effectiveness, making it attractive for smaller stone burdens and in settings where resources are limited. Its main drawbacks are reduced efficiency for larger fragments and the need for alternating irrigation. CVAC, on the other hand, provides continuous suction and irrigation, superior clearance in larger stone burdens, and randomized trial data supporting long-term clinical benefits. The trade-offs are higher cost, larger instrument size, and a steeper learning curve. Of note, to make room for the larger aspiration channel, the CVAC scope has an extremely small camera with decreased visibility compared with the DISS scopes.

Clinical Impact

Both technologies expand the armamentarium of endourologists. For small to moderate stones, DISS provides a practical option with minimal additional investment. For larger, more complex stones, CVAC appears to offer more complete clearance, lower retreatment rates, and improved durability of outcomes. As these platforms evolve, surgeons will increasingly be able to tailor suction strategies to patient anatomy, stone size, and institutional resources.

Conclusion

DISS and CVAC are complementary rather than competing technologies. DISS provides simplicity and affordability, whereas CVAC delivers efficiency and superior clearance in challenging stone burdens. The future of ureteroscopic stone surgery will likely involve both systems, matched to the right patient at the right time.