Inhibition of Ureteral Smooth Muscle Contraction by Vibration: A Possible Aid at Transurethral Stone Extraction

Abstract

Since mechanical vibrations reduce the contractile force in smooth muscle (Ljung & Sivertsson, 1972) it was studied whether such vibrations would also facilitate transurethral stone extraction. A modified Dormia catheter was used. Vibrations were induced by attaching the metal rod, operating the basket unit, eccentrically to the axis of an electrical motor. The longitudinal tension in an isolated dog ureter (i.e. the resistance against introduction and withdrawal of the catheter) was recorded when the catheter was moved at a constant speed inside the ureter.

The tension recorded was considerably lower with than without vibrations when the catheter was forced past a fixed concernment as well as when a stone, caught in the basket, was extracted. This tension difference was eliminated when the experiments were repeated in Ca⁺⁺-free Krebs solution, in which the smooth muscle cells are unable to contract actively. The results, therefore, suggest that vibrations act by interfering with the development of active smooth muscle tension.

At conventional transurethral stone extractions, it is often difficult both to pass and to extract the stone with the catheter. The present results indicate that these difficulties might be considerably reduced by using a vibrating catheter.