Electrohydraulic intracorporeal lithotripsy of salivary duct stones – in vitro and animal investigations

Summary

Background: The performance potential of extracorporeal lithotripsy as a method for the treatment of salivary duct stones has been demonstrated in the scope of routine clinical applications. The question thus arises whether electrohydraulic intracorporeal lithotripsy as applied in urology and gastroenterology might equally serve as a useful method for curing sialolithiasis. Materials and methods: (a) In vitro experiments: 58 salivary duct stones and 11 extirpated human submandibular glands were treated by three different electrohydraulic modalities, (b) Animal experiments: The dilated Stensen's duct and several other types of tissue (muscle, parotid gland, facial nerve) of six rabbits were exposed to electrohydraulic Shockwave immission. Results: 53 out of 58 salivary duct stones (91%) were fragmented, 39 (67%) of which had a residual stone diameter of less than 1.5 mm and 14 (24%) of more than 1.5 mm. No effects were observed in five cases only. Fragmentation remained independent of the mineralogical stone composition and the type of implemented lithotriptor. The smaller the diameter of the probe and the larger the stone, the higher the number of Shockwaves that was required for fragmentation. Complete fragmentation could not be achieved with the smaller probes. In human submandibular glands detectable tissue lesions could be macroscopically and histologically evidenced after application of electrohydraulic shockwaves in vitro. Immission of electrohydraulic Shockwaves into the dilated Stensen's ducts of rabbits led to duct perforation after one to five single pulses. Furthermore, lesions of nerves and blood vessels were observed in the environment of the duct. These effects occurred with all the employed electrohydraulic devices, and with the entire range of applied probe diameters and intensity levels. In our opinion, the induced damage is probably the combined result of the direct effect of the plasma and of the resultant stress wave. Conclusions: Indications of the described method for the treatment of stones in narrow human salivary ducts should be clearly restricted due to the high risk of serious damage to tissue.

Key Words:

• salivary stones
• sialolithiasis
• electrohydraulic intracorporeal lithotripsy