Risk of intestinal damage from endoscopic Neodymium-YAG laser irradiation of bladder tumors

The danger to the intestine that is inherent in the thermal effects of endoscopic irradiation of urinary bladder tumors with the Neodymium-YAG laser was examined using experimental animal research. Temperatures of 700C when applied over a period of 4 s will already lead to extensive damages to the intestine including the danger of perforation; the same holds true for temperatures of 640C applied over 7 s, 600C over 15 s and 550C applied for 61 s or longer. The intestine is more sensitive to heat than the bladder and therefore more vulnerable. There is an added risk involved when irradiating parts of the bladder wall that are particularly thin due to a previous resectioning of tumors, or in cases where the water-filled bladder is overly distended. Principally, there is a much higher damage risk inherent in power increases with the resulting increases in temperature. The following statements can be made concerning clinical endoscopic application of the Neodymium-YAG laser while keeping in mind that there are familiar limiting factors set to the validity of drawing conclusions from animal experiments and applying them to man: intestinal damages which entail the danger of perforation will be avoided, when the laser power is kept at a maximum of 42 Watts, applied over periods of maximally 3 s, with a focus of at least 2 mm, onto bladder areas that measure at least 3 mm in thickness. It appears that transmural necroses of infiltrated bladder wall areas are more likely to be achieved without endangering the intestine when using lower powers and greatly prolonged application periods instead of the presently used higher powers of around 40 Watts and the short application periods of 2 to 3 s. (orig./MG)