Mar Vista Animal Medical Center

3850 Grand View Blvd.
Los Angeles, CA 90066

(310)391-6741

www.marvistavet.com

LITHOTRIPSY FOR STONE REMOVAL

"Lithotripsy" is a funny word for a minimally invasive alternative to urinary stone removal surgery. "Lith" means "stone" and "tripsis" means "crushing" so, in short, lithotripsy refers to the breaking up of stones so that the fragments are small enough to pass. No cutting is involved.

There are two types of lithotripsy: intracorporeal laser lithotripsy and extracorporeal shock wave lithotripsy. The gadget that breaks the stone or stones up is called a "lithotripter."

EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY

This form of lithtripsy is used to fragment stones in the upper urinary tract: the kidney and ureter. To break up the stone, the patient is anesthetized and a shock wave is focused on the stone. The shock wave must propagate in water so the patient is either partially submerged in a water tank or a “water cushion” is applied to the patient. Commonly over a thousand shocks are delivered to the patient. Certain types of stones are more amenable to this form of fragmentation (calcium oxalate stones are especially amenable while urate stones, for example, are not). Stones in the kidney (versus those in the ureter) are more easily fragmented.


(original graphic by marvistavet.com)

Shock wave lithotriptor
(Photocredit: DiverDave via Wikimedia Commons)

ADVANTAGES OVER SURGICAL STONE REMOVAL

  • Cutting into the kidney virtually always reduces kidney function afterwards. Kidney function is better preserved with lithotripsy.
  • Less invasive to the patient.

 

DISADVANTAGES OVER SURGICAL STONE REMOVAL

  • Special equipment is required and availability is limited to specialty practices and universities.
  • Approximately 10% of cases where lithotripsy was used to fragment a kidney stone ended up with a stone fragment obstructing a ureter. This requires some additional treatment (either another lithotripsy, surgery, medical management etc.)
  • Approximately 2-3% of cases will develop pancreatitis from the shock waves.
  • In order to submit stone fragments for analysis, they must be collected/found after they are passed by the patient.
  • It can take several months to pass all the stone fragments.
  • 30% of dogs are likely to require a second procedure to complete fragmentation of kidney stones. If the stones were in the ureter, 50% of dogs required more than one procedure.

 

INTRACORPOREAL LASER LITHOTRIPSY

Laser Lithotriptor
(Photocredit: Courtesy of ACCESS Specialty Animal Hospitals
Used with permission)

With this technique stones can be removed from the lower urinary tract (bladder and urethra). A special laser, called a holmium:YAG laser, is used to break up the stone and endoscopy is needed to get the laser right up to the stone where the patient’s tissues are not in the way.

The endoscope which is used in the urinary tract is called a “cystoscope” and must penetrate the very narrow urethral opening of a small animal. Some animals are simply too small for the procedure. Once the cystoscope is in position, the laser uses heat to create water vapor bubbles which rapidly expand and collapse. If these bubbles are in contact with the stone, the crystal structure of the stone is disrupted and the stone fragments. The fragments are either allowed to pass, are removed via the cystoscope's collection basket, or are expressed from the bladder manually ("voiding urohydropropulsion").

cystoscope

If the stone is in the urethra, disruption of the stone is easiest. If the stones are in the urinary bladder matters become more complicated. Issues that prevent success include the diameter of the urethra, hemorrhage obscuring the view of the stone or hampering the laser’s contact with the stone, accidental damage to the bladder from the laser, and prolonged anesthesia time because it is taking so long to fragment the stone(s). Despite these potential problems, studies have reported 83-96% success (i.e. complete stone removal) in female dogs and 68-81% success in male dogs.

Cystoscope                         
(Photocredit: MykReeve via Wikimedia Commons)

ADVANTAGES OVER SURGICAL STONE REMOVAL

  • Patients discharged sooner (often the same day as the procedure).
  • Less invasive. No cutting required.

DISADVANTAGES OVER SURGICAL STONE REMOVAL

  • Special equipment is required. Availability is limited to specialty hospitals.
  • Procedure generally takes longer than surgery. Longer anesthetic time. Same depth of anesthesia required as with surgery.
  • Generally more expensive than surgery.
  • Not an option for male cats or small male dogs.
  • If numerous stones are present, lithotripsy is not efficient and surgery should be performed instead. The facility local to us recommends against lithotripsy if there are more than 5 stones present.
  • If the stones are large it may not be time efficient to use lithotripsy (the facility local to us recommends against lithotripsy if there is more than one stone of ½ inch or more in diameter).
  • Because lithotripsy can wash an infection backward and up into the kidneys, culture of the urine should be performed prior to the procedure.  Infection also leads to some urethral swelling which makes introduction of the cystoscope more difficult. Any infections should be controlled as best as possible prior to the procedure.

If you are interested in this procedure as an alternative to surgery, notify your veterinarian to find out if there is a facility near you that is equipped for lithotripsy. 

 Page posted: 11/25/09
Page last updated: 6/18/2016