Breaking Stones Lithotripsy Procedure

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 breaking stones into fragments 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 lithotriptor.

Extracorporeal Shock Wave Lithotripsy

This form of lithotripsy is used to fragment stones in the upper urinary tract: the kidney and ureter. 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 (for example, calcium oxalate stones are especially amenable, while urate stones are not). Stones in the kidney, compared to those in the ureter, are more easily fragmented.

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

  • Specific 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 (another lithotripsy, surgery, medical management, etc.)
  • Approximately 2 to 3% of cases will develop pancreatitis from the shock waves.
  • In order to submit stone fragments for analysis, they must be collected or 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. For stones in the ureter, 50% of dogs require more than one procedure.

Intracorporeal Laser Lithotripsy

With this technique stones can be removed from the lower urinary tract (bladder and urethra). A specific type of 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 that is used in the urinary tract is called a cystoscope and must penetrate the 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 that rapidly expand and collapse. If these bubbles are in contact with the stone, the crystal structure of the stone is disrupted. The fragments are either allowed to pass or are removed via the cystoscope.

If the stones are 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.

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

  • Specific equipment is required, and its 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. Some facilities recommend against lithotripsy if the pet has more than five stones.
  • If the stones are large it may not be time efficient to use lithotripsy (some facilities recommend against lithotripsy if there is more than one stone of a half inch or more in diameter).
  • Because lithotripsy can wash an infection backward and up into the kidneys, a culture of the urine should be done before 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.

 

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