Laser photoirradiation of the canine ureteral orifice: comparison between contact and noncontact techniques

We studied the long-term effects of Nd:YAG laser photoirradiation in 17 canine ureteral orifices, comparing results of the contact and noncontact (free-fiber) techniques. The noncontact technique damaged four of eight ureters, causing ureteral obstruction with significant hydronephrosis in three and reflux in one. The amount of energy used correlated with the subsequent appearance of ureteral obstruction; obstruction developed in both cases when 3,000 and 3,300 joules were used but in only one of five cases when less than 2,300 joules were used. In contrast, the contact technique, using 350-800 joules, caused no hydronephrosis and only one case of reflux. Since these animal studies clearly document that the Nd:YAG laser may significantly damage the ureter, particularly when the noncontact technique is used, we recommend that the surgeon consider the contact technique to reduce the risk of ureteral damage and use the smallest amount of energy required for adequate tumor eradication when treating tumors in or near the ureteral orifice.