Cutting laser systems for ureteral strictures

Acquired ureteral strictures are still treated either with a stent, balloon dilatation, by open surgery or by endoscopic therapy with a "cold knife" or high current density as intubated ureterotomy. The success rates described in the literature range between 50% - 90%. Using the experimental CTHrYAG laser (wavelength 2120nm) and CTrYAG laser (wavelength 1950nm), the reduction of invasiveness and of morbidity was evaluated. First the CTHrYAG laser was investigated on 540 fresh porcine ureters variing the following parameters: fiber diameter (100pm - 600pm), cutting speed (0,25/0,5/1 mm/s), power (1-6W), pulse width (550-750pm free running mode). With a computerized morphometry system, defect depth, defect width, coagulation depth and coagulation width were measured. Then 21 female pigs underwent 7.5F -12F ureteroscopy with CTHrYAG laser, CTrYAG laser, high current density and "cold knife" ureterotomy. An IVP and sacrification with explantation of the whole urinary tract was done on day 6 and arround day 60. The best cutting quality was seen with the 200/300 pm fiber at a power range between 3 to 5 W for the in-vitro experiments. 6 of 9 pigs treated with non-laser cutting systems had a poor outcome (retrop. hematoma, pyo- or hydronephrosis), 9 of 12 pigs showed excellent or good outcome. In practise, laser application via the endoscope was easy to handle and exact cutting was always seen. The CTrYAG laser seems to have the best success results with low ureteral stricture recurrence rates. However, it's clinical use remains to be proven.