UMN VMC Lithotripsy Referrals

Take abdominal radiographs to estimate stone number and size 

• A single lateral is often sufficient.

• Make sure the entire urethra is included; in male dogs, pull legs forward or backwards if needed to see the region of the proximal os penis, as this is a common site for urethral stones.

• Note: Ultrasound images have poor accuracy for estimating stone number and size, thus radiographs are needed as well.

Estimate the most likely stone composition

• The Minnesota Urolith Center free app (MN Urolith) has CALCulator and CALCurad tools to help estimate stone compositions.

• Note for predictions in dogs:

  • In general, younger female dogs are most likely to have struvite, especially if there is evidence of an infection (pyuria and/or bacteriuria) and an alkaline urine pH.

  • In general, older male dogs are most likely to have calcium oxalate, especially if there is no evidence of infection and an acidic urine pH.

If struvite is likely, try medical dissolution first for a minimum of 2 weeks (if no dissolution is present at that time, struvite is much less likely)

• Instructions for struvite dissolution for dogs

• Instructions for struvite dissolution for cats

Check that the signalment and weight will accommodate the cystoscope needed for lithotripsy (8 Fr or greater)

• Dogs: 

  • Females - With the exception of extremely petite dogs (4 kg or less), we can do lithotripsy on female dogs.

  • Males - We can generally do lithotripsy on male dogs >7 kg. If they are 5-7 kg or if you suspect a narrow urethra (e.g., previous urethral stones or surgery), please try passing an 8 Fr catheter before referring. The catheter must be able to pass easily (minimal to no resistance). If there is any resistance, do not force it and do not try to push urethral stones back into the bladder with the catheter (use flushing).  If the dog is <5 kg, other options should be considered (surgery if clinical versus active surveillance if subclinical).

  • Note: For female and male dogs, there is also the option of voiding urohydropropulsion. This does not require the cystoscope and is thus not limited by the size of the animal. However, it is limited by the size of the stones. In general, we can void stones ≤ 2 mm in a male dogs and ≤ 3 mm in a female dog.

• Cats:

  • We can only perform lithotripsy on female cats.

Check that the stone burden or size is not too large for lithotripsy

• Dogs: 

  • If there are multiple stones >8 mm or one very large stone (>15 mm), lithotripsy is unlikely an option unless it is a very large dog.  If the owners are motivated and okay with the risk of needing to convert to surgery if lithotripsy is unsuccessful, please email radiographs to samvet@umn.edu for one of the endourology faculty to triage. Include the dog's signalment, weight, urinalysis, and any other pertinent labwork. 

Cats: 

• • We only recommend lithotripsy for cats with 1-3 stones present that are all <5 mm.

Provide the owner with a rough estimate of the cost

• As of 2025, $4,000-5,000 is typical. Cost is sometimes lower if only basket retrieval is needed or if we can retrieve all stones with voiding urohydropropulsion.

Submit the VMC referral form

• State on the referral that the purpose is lithotripsy and that you have gone through the step-by-step process 

Confirm that the cat is stable and does not require urgent/emergency treatment

• While burst wave lithotripsy (BWL) fragments stones, it can take time for the fragments to separate from each other and pass. Further a second treatment is needed for most cats. Therefore, we recommend prioritizing surgical options for cats that are rapidly progressing and severely ill. 

Use ultrasound to confirm that the ureteral stone can be visualized with this modality and is obstructing

• We use ultrasound to target the stone during BWL and thus must be able to locate the stone with this imaging modality. 

• We only recommend treating ureteral stones if there is renal pelvic dilation and ureteral dilation present proximal to the stone to support that it is at least partially obstructing. 

• Note: If the stone was identified on radiographs and ultrasound is not readily available at your clinic, we will accept referrals for us to evaluate the case further to determine if the stone is obstructing and can be treated with BWL.

• Note: Treatment is rarely recommended for kidney stones. It is only considered when suspected to be a nidus of infection. 

Check that the stone size is appropriate 

• Our current BWL system is designed for stones measuring 1-4 mm in at least one dimension. This size range is typical for ureteral stones in cats. While we can fragment slightly smaller stones (0.5-1 mm), stones >4 mm in all dimensions will not fragment effectively. 

• Note:  Stones that are >3 mm in all dimensions (length, width, and height) fragment slowly, and two treatments are often needed.

Check that the stone depth is appropriate

• Our current BWL system can only treat stones located within 4 cm of the body wall on ultrasound. 

• Note: Cat ureteral stones are almost always within this depth, as they are often shallow (<2 cm from the body wall). In dogs, depth can be more of a limiting factor.

Provide the owner with a rough estimate of the cost

• For outpatient treatment, a single BWL treatment is approximately $2,500-3,000. We strongly recommend estimating for two treatments  at $5,000-6,000 because a second treatment is needed in most cases.  

• These estimates do not include diagnostic imaging (e.g., urinary tract ultrasound with a radiologist interpretation) or hospitalization, which might be recommended depending on the individual patient.

Set owner expectations for efficacy

• Based on cats treated to date,  BWL has about a 70% efficacy rate after two treatments. In a subset of cases, a third treatment is recommended. 

  • For comparison, medical management is estimated to have a 10-30% success rate with small (<2 mm) distal stones being most likely to pass. 

  • Placement of a subcutaneous ureteral bypass (SUB) device is offered through our surgery service. Approximately 80-95% of cats survive surgery. Most complications occur over time and include SUB occlusion from mineralization and recurrent infection.  Regular flushing of the SUB device is recommended after placement. If you are interested in SUB placement, please send a referral to the surgery service.

• We have only treated one dog to date and cannot provide estimates on efficacy in dogs.

Submit the VMC referral form

• State on the referral form that the purpose is BWL with Dr. Eva Furrow and that you have gone through the step-by-step process. 

• Please also send any available diagnostic imaging of the urinary tract with the referral.