EXTRACORPOREAL ULTRASOUND EXPOSURE BY AMPLITUDE-MODULATED SIGNAL FOR PREVENTION OF INCRUSATION OF URETERAL STENTS IN A CHRONIC EXPERIMENT

Introduction. Ureteral stents are widely used as drainage for the upper urinary tract. Incrustation and biofilm formation are the most dangerous complications of this type of drainage, leading to its failure. None of the existing methods completely solve the problem of preventing these complications. Purpose of the study: to assess the effectiveness and safety of the usage of extracorporeal acoustic exposure by ultrasonic amplitude-modulated signal for the prevention of incrustation of ureteral stents in a chronic experiment. Materials and methods. A team of authors calculated, designed and manufactured an ultrasonic generator, the main principle of which is the generation of an amplitude-modulated ultrasonic signal. 10 somatically healthy mongrel dogs without urinary tract infections were included in the experiment. Bilateral ureteral stenting was performed on the animals. Standard polyurethane stents 5CH were used. Starting from the 7th day of the postoperative period, ureteral stents were extracorporeally affected by the amplitude-modulated ultrasonic signal in their projection, leaving the contralateral stents intact. On the 28th day of the experiment, the stents were removed, the weight of each of them was measured, and their surface was examined by scanning electron and atomic force microscopy. Morphological examinations of the ureters and descending part of the colon on the side of the acoustic impact were carried out. Results. No complications in the postoperative period were observed. After extraction, the average weight of the sonicated stent was 0.5711±0.0264 g, the intact one - 0.6218±0.0296 g (p - 0.0022497). The surface of the new stent has thin rows of small technological defects revealed by scanning electron and atomic force microscopy. On the surface of the sonicated stent, salt deposits are noted, but this array is loose, fragmentarily repeating the technological shading of the new stent. On an intact one stent, striation is lost, formations of a rough monolithic structure with massive relief defects are visible. Atomic force microscopy: the height of technological irregularities on the surface of the new stent was 0.15±0.02 qm; on the sonicated stent, the average height of salt deposits was 0.2382±0.0988 μm, with an average maximum of peaks - 0.8564±0.5013 μm. On an intact stent, the average height reached 1.2470±0.6559 μm, and the average maximum of peaks was 3.1021±1.3844 μm. Histological examination: the severe of damage to the urothelium in both groups was comparable. The revealed changes did not worsen by exposure of amplitude-modulated ultrasonic signal. The hypertrophy of muscle fibers was noted in the sonicated ureteral wall. These findings are explained by the reflex increasing of peristalsis during vibration of a foreign body in the lumen of the ureter by the exposure of ultrasound. Morphological manifestations of traumatic damage to the colon were not revealed. Conclusions. Extracorporeal ultrasound exposure by amplitude-modulated signal is an effective and safe way to prevent incrustation of ureteral stents, which requires further study and adaptation to clinical practice.

ureteral stent, encrustation, incrustation, biofilm, ultrasound