1989 Volume 80 Issue 9 Pages 1278-1285
Ultrasound lithotriptors (USL) and electrohydraulic lithotriptors (EHL) are representative lithotriptors for endoscopic eliminaiton of upper urinary tract stones. However, they have some disadvantages. For example, USL can not be used with flexible scopes and EHL can cause unexpected tissue injury. To overcome these problems, the pulsed dye laser lithotriptor (MDL-1, Candera Co.) was developed. The characteristics of this laser lithotriptor and its direct effects on tissue was investigated.
This pulsed dye laser lithotriptor generates a 504nm wavelength green light beam by using a combination of a xenon flash lamp and the greenish dye composed of coumarin solution. The maximum output energy is 60mJ/pulse and the pulse duration is 1.5 microsecond. The pulse rate can be varied from 1 to 20Hz.
First, the intensity of the shock wave was measured by using a combination of a piezoelectric element and an oscilloscope, and then, the results were compaired with those obtained by a similar experiment with an EHL. The average intensity of the shock wave was 54.4mW under the conditions of 40mJ/pulse of output energy and 10Hz of pulse duration. On the other hand, the EHL generated an average of 54.7W under the conditions of 400mJ/pulse output energy. Then, fragmentation of various kinds of urinary stones in saline solution was performed. The results showed that this lithotriptor could fragment almost all kinds of stones except cystine stones. Then, hen's eggs were used to observe the effect if laser bean influenced on the organism immediately behind the photoradiated object. Only the egg shell was demolished but the egg membrane below the eggshell did not undergo any change. After these experiments, skin, liver, kidney and urinary bladder of nude mice and human prostatic urethral mucosa in case of TUR-P were irradiated by this laser. The results showed that laser energy caused slight penetration and localized hemorrhage from the surface of epithelium to subcutaneous tissue. It was confirmed that these effects were generated when the tip of the quartz fiber was in direct contact with the object.
After these investiagtions, fragmentation using this laser lithotriptor was attempted in thirty cases of upper urinary tract calculi. These 30 cases involved five cases of renal calculi and 25 cases of ureteral calculi. Percutaneous nephrolithotomy (PNL) was performed in 22 cases and transurethral ureterolithotomy (TUL) was performed in 8 cases. Twenty-four stones (80%) were fragmented successfully. However, in six cases, stones which were smooth surfaced, hard and large could not be fragmented. The side effects of laser lithotriptor, slight hemorrhage from the ureteral mucosa, was observed in 2 cases.
We think that this laser lithotriptor is one of the most effective instruments for fragmenting urinary stones by TUL, especially TUL with a flexible scope, because this lithotriptor uses a very thin flexible quartz fiber and it dose not require protection of tissue from injurying while fragmenting calculi.
