In the 1970s, it was fortuitously recognized that shock waves generated by collision with raindrops produced unusual pitting
patterns on the metal surface of supersonic aircraft during high-speed flight.
Researchers theorized that the elliptical contour of one part of the plane's fuselage resulted in the convergence of shockwaves
onto another focal point of the aircraft, accelerating metal fatigue. Based on these observations, scientists at Domier, a
German aerospace firm, embarked on a program to develop a system for the production of shock waves that could be reproducibly
focused at a solitary point with the goal of fragmenting urinary stones.
This technique was called extracorporeal shockwave lithotripsy (ESWL). On Feb. 7, 1980, at the University of Munich, ESWL
was used successfully to fragment uroliths in the kidney of a human patient (Chaussy 1989). Since that time, the development
of ESWL has become a smashing success in terms of revolutionizing treatment of uroliths in man. Extracorporeal shock wave
lithotripsy was followed by the development of intracorporeal techniques whereby instruments used to generate high-energy
wavelengths were applied directly to the surface of uroliths viewed through an endoscope. Compared to surgery, lithotripsy
is highly effective, minimally invasive and associated with less risk to the patient. Notably, use of ESWL shock wave lithotripsy
and intracorporeal endoscopic laser lithotripsy to treat human patients with uroliths resulted in a significant reduction
in iatrogenic loss of renal function associated with surgical intervention (Holman 2002).
Widespread knowledge of the success of extracorporeal and intracorporeal techniques of lithotripsy to treat kidney and ureteral
stones in humans promoted veterinarians to consider its feasibility to manage uroliths in dogs. The result was development
of effective protocols for ESWL to treat kidney and ureteral stones in dogs (Adams 1999). However, the majority of naturally
occurring uroliths in dogs are located in the lower urinary tract rather than the kidneys and ureters. For example, uroliths
from more than 200,000 dogs have been submitted to the Minnesota Urolith Center for analysis since 1981; in 98 percent of
cases, uroliths were retrieved from the urinary bladder and/or urethra.
Unfortunately, ESWL is not a reliable form of treatment for bladder stones because of their tendency to move out of the focal
point of converging shock-waves. Movement of the uroliths does not allow repeated shock waves to converge on a solitary point,
resulting in reduced fragmentation. Fortunately, this obstacle has been over-come by fragmenting bladder stones with the aid
of cystoscopes to guide various types of newly developed lithotriptors directly to the stone's surface. Although several forms
of energy (electrohydraulic, ultrasonic, ballistic) can be delivered through the cystoscope, holmium:YAG laser technology
effectively fragments all types of biogenic stones in dogs (Wynn 2002).
As illustrated in the following case report, cystoscopic laser lithotripsy is an effective alternative to surgical removal
A 5-year-old female spayed Miniature Schnauzer was referred by a colleague in Arizona to the University of Minnesota Veterinary
Teaching Hospital because of a two-year history of recurrent bladder stones. Urocystoliths removed one year previously were
composed of 95 percent magnesium ammonium phosphate and 5 percent calcium phosphate carbonate. Since that episode, this patient
was fed canned and dry formulations of an adult maintenance food designed to reduce magnesium and to promote formation of
Physical examination revealed an alert dog weighing 12 kilograms. Temperature (102° F), respirations and pulse rate were normal.
Serum concentrations of creatinine (1.1 mg/dl), urea nitrogen (SUN = 19 mg/dl), phosphorus (3.5 mg/dl), calcium (10.7 mg/dl)
and bicarbonate (20 mmol/L) were normal. Results of a hemogram revealed values within the normal reference range (hematocrit
= 56 percent and WBC = 7,880/ul). Analysis of a urine sample collected by cystocentesis prior to any form of therapy revealed
that specific gravity was 1.032. The urine was alkaline (pH = 8.0) and contained numerous red blood cells (>50/hpf).
White cells and epithelial cells were not detected in urine sediment. However, a few amorphous calcium phosphate crystals
were observed. Aerobic culture of an aliquot of urine collected by cystocentesis did not result in in-vitro growth of bacteria.