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[Changes in physical characteristics of endourologic catheters caused by shock waves].

OBJECTIVE
To analyze the shock wave effects on double-J stent.


METHODS
Retention strength modifications induced by shock waves were analyzed: a) 60 double-J stents obtained from patients were compared (20 had not been treated by ESWL; 20 had been treated by piezoelectric-ESWL and 20 by electrohydraulic-ESWL; b) the effects of piezoelectric-ESWL were determined in vitro using 36 stress-tested double-J stent segments (Urosoft, C-Flex and silicone) vs. a control group.


RESULTS
The retention strength of the stents from ESWL-treated patients, especially those that had been submitted to piezoelectric-ESWL, was lower than in stents from patients that had not undergone ESWL (p < 0.05). The foregoing has been corroborated by the in vitro findings. The impact frequency causing maximum damage is specific for each material. Microphotographic studies revealed fracture lines on the surfaces of the ESWL-treated stents (Urosoft and C-Flex).


CONCLUSIONS
The foregoing findings may explain the high incidence of double-J stent migration observed in ESWL-treated patients.