Introduction: The vapor tunnel (VT) technology is a result of the pulse modulation during holmium laser emission: it consists of a single specific long pulse, using the minimum peak power in accordance with selected output settings. The first part of the pulse creates a vapor channel, whereas the remaining energy is discharged immediately after, passing through the previously created tunnel. We present the outcomes of this technology in the treatment of ureteral stones.
Methods: 210 patients with ureteral stones were randomly assigned to holmium laser lithotripsy with or without the VT technology (105 patients per group). The 35 W-LithoEvo laser generator (Quanta System) with 365 µm fibers were used for all cases. Energy and frequency settings were 1 J and 12 Hz in both groups. After the procedures, a ureteral stent was always positioned and removed 20 days later. We compared dusting time, total procedural time and stone retropulsion, graded on a Likert scale from 0 to 3 (maximum retropulsion). We also compared postoperative ureteral lesions with the Posturetroscopic Lesion Scale (PULS). The success rate of the two techniques was based on stone-free rate at 1 month.
Results: The two groups were comparable in terms of age and mean preoperative stone size (1.1 vs 1.0 cm, p> 0.05). The VT technology was associated with significantly lower (p> 0.05) dusting time (15.3 vs 9.7 minutes), total procedural time (37.2 vs 25.7 minutes), total delivered energy (19.9 vs 7.7 kJ), and retropulsion (Likert score 3 vs 0). Patients in the first group required stone fragments' retrieval with a Tipless Basket (Kobot Filter; RocaMed) and presented a higher rate of PULS-1 ureteral lesions than the VT group: 37 (35.2%) vs 8 (7.6%) patients, p< 0.05. Whereas the VT setting allowed complete dusting of the stones. We registered six cases (5.7%) of postoperative ureteral strictures in the first group vs none in the VT group, p< 0.05. Stone-free rate at 1 -month was comparable (88.6 vs 93.4%, p> 0.05).
Conclusions: The VT technology is associated with significantly lower dusting time and total procedural time, because of reduced retropulsion of the stone, which makes it more precise, quicker, and easier to perform. It also allows complete dusting, with no need for fragment retrieval, reducing possible ureteral lesions. These features make VT an excellent setting option in an urgent setting, when the ureteral wall is more vulnerable.