The new generation super-mini percutaneous nephrolithotomy (SMP) system: a step-by-step guide

Abstract

Objective: To present our novel miniaturised endoscopic system and describe a step-by-step guide for successful implementation of the super-mini percutaneous nephrolithotomy (SMP).

Patients and methods: The new-generation SMP endoscopic system consists of (i) a 40 000-pixel super-mini nephroscope with an 8.0-F outer diameter and 7.5-F inner diameter dismountable sheath, and (ii) a newly designed irrigation-suction sheath available in either 12 F or 14 F. The irrigation-suction sheath is a two-layered metal structure. The key feature of the irrigation-suction sheath is to allow irrigation and suction respectively (the inflow through the space between the two layers of the sheath, the outflow through the central lumen of the sheath). This property improves irrigation and stone clearance despite reduced instrument dimension. In all, 59 patients with renal stones underwent new-generation SMP between April 2016 and December 2016. The percutaneous tract dilatation was carried out to 14 F. Lithotripsy was performed using either holmium laser or a pneumatic lithotripter. Stone fragments were sucked out by vacuum suctioning through the sheath. A nephrostomy tube or JJ stent was placed only if clinically indicated. Low-dose computed tomography was performed to assess the stone-free status on the morning after the procedure.

Results: The mean stone burden was 2.4 cm. Of the 59 patients, nine had diabetes and five had hypertension. SMP was completed successfully in all patients with a mean operation duration of 32.9 min and a mean haemoglobin decrease of 13 g/L. The stone-free rate was 91.5%. Complications occurred in 5.1% of the patients, all of them were Clavien-Dindo Grade I (minor fever managed by antipyretic therapy), and no transfusions were needed.

Conclusion: The new-generation SMP system is safe, feasible, and effective for managing renal calculi of <3 cm, with the advantages of a small percutaneous tract, less blood loss, high efficacy in stone clearance, improved visual field, short operation duration, and ease of operating.

Keywords: SMP; irrigation-suction sheath; miniaturisation; percutaneous nephrolithotomy; renal calculi.