Voiding Urohydropropulsion For Removal Of Urinary Stones In Dogs And Cats

Voiding urohydropropulsion.

Sophie had successful urohydropropulsion this week, removing many small stones.

Wow! That’s a mouthful!

Let’s break it down: “Uro” is a Latin prefix referring to the urinary tract. “Hydro” refers to water, or, more broadly, any liquid. “Propulsion,” from the Latin propellere, meaning “to propel,” “the act of driving forward.”

Voiding urohydropropulsion, then, is the act of using a liquid to expel something from the urinary tract. More specifically, we are using a physiologic solution in the bladder to remove urinary bladder and urethral stones. This technique cannot help stones that are in the kidney(s) and/or ureters.  However, unlike people, dogs and cats form more stones in their bladders than in their kidneys.

The technique was developed by Dr. Jody Lulich at the University of Minnesota Urolith Center.

The steps are fairly straightforward. It can be practiced in the wide-awake, sedated or fully anesthetized patient. First, aseptically (using a sterile technique), introduce a urinary catheter. Second, instill physiologic saline or lactated Ringer’s solution into the bladder to distend it. Care must be taken not to overdistend and rupture the bladder. Third, place a finger onto the urethra to prohibit flow while removing the catheter. Fourth, orient the patient with the spine vertical (standing up like a human) and have an assistant squeeze the bladder, after which the finger inhibiting flow is removed. The result should be a rush of urine and solution from the bladder, the goal of which is to carry urinary bladder stones in the flow.

Of course, the size of stones that can pass is proportional to the size of the patient’s urethra, which is roughly proportional to the overall body size.  While the procedure can theoretically be used in female cats, it’s going to work on only on the largest queens with the smallest stones. Male cats’ urethras are much to small for VU to be practical.

A pet with a really large cystic calculus (bladder stone) is going to need cystotomy: opening the abdomen, incising the urinary bladder and removing the stone that way.

One of the giant advantages of voiding urohydropropulsion is the fact that tiny granules of stone material that might be missed or overlooked in an open surgical technique are more likely to be flushed out.

The procedure can be repeated as many times as necessary, although the practitioner must take into account that inflammation of the urethra and bladder lining occur with each passage of the catheter.

Still, it is much less invasive and less irritating than cystotomy.

We used the technique successfully on little Sophie (pictured above) this week. Observe the many stones visible on the preoperative radiograph (X-ray),

No stones can be seen after the procedure.
Sophie’s pretreatment radiograph. Notice the many stones.

and the total absence of stones on the post-treatment film.

The stones have been sent to the University of Minnesota Urolith Center, where quantitative analysis will tell us whether Sophie has a recurrence of calcium oxalate calculi.

See you next week, Dr. Randolph.


  1. Hi,
    My dog had a cystotomy one year ago, and he formed again some stones cc in his bladder, now the Vet recommend
    voided urohydropropulsion ( +\ – PCCL procedure ) he doesn’t have any symptoms or discomfort right now, So it is safe he has this procedure again?

    Thank you

    • Only your attending veterinarian can address questions of safety and applicability. That said, I have plenty of patients who have had repeated cystotomies and both procedures have excellent safety records. Thanks for reading, Dr. Randolph.

  2. My vet detected two 2-3 cc stones in my cat by ultrasound and x-ray. She proposed voiding urohydropropulsion and said it would be done under general anesthesia. You note, however, that this procedure can done done fully awake, sedated or under general anesthesia. Can general anesthesia always be avoided?

    • If, in fact, these stones are three cubic centimeters in size it’s going to be a challenge to remove them with VU. General anesthesia will maximize the relaxation of the urethra, making room for the stones to pass. Please read this article and these articles about making anesthesia safe. Thanks for reading, Dr. Randolph.

    • Sorry, Ann, but there is no way for me to know, as there is no database on the practice. Did you ask your veterinarian? Practicing in your area, he would be better able to answer the question. It’s not a terribly difficult procedure, so it’s entirely possible that he does it! If not, he should be able to refer you to someone nearby who does, even if it’s a nearby teaching hospital. Please write back and let us know how your pet does. Best wishes, Dr. Randolph.

      • Dear Dr. Randolph, We have 2 mini Schnauzers who will undergo surgery this wk for bladder stones this will be 2nd surgery for 1. I am very confused as to what to feed them. They have been on chicken w/rice (cooked by me) and Canin S/O which concerns me since it is 100% grain no protein. Is protein bad for Struvite stones? Thank you! Barbara Tedesco

        • Thank you for an excellent question, Barbara, and an opportunity to inform others who may face the same challenge. The use of diet to dissolve and/or prevent stones is a very exacting science. Adding other foods, regardless of whether it’s another balanced diet or imbalanced supplementation like chicken and rice, can interfere with the prescription diet’s efforts to starve the urine of the building blocks the stone needs in order to form. In the case of struvite, that’s ammonium ions, magnesium and phosphate. As you might imagine, that’s not the whole story. Some patients need supplements to adjust the pH of the urine, and, sometimes our efforts to prevent struvite stones results in formation of calcium oxalate stones. I’ve often said, “There is nothing simple about the practice of medicine.” As for protein, all reputable brands of commercial foods are formulated with the proper balance of nutrients, including protein. Royal Canin is a reputable brand. Just because the protein source is vegetable and not animal doesn’t make it bad. Or good. It is just an alternative method of reaching the same goal of a balance of nutrients. Don’t hesitate to ask your veterinarian to explain your Schnauzers’ problems again, from the top. These things are complicated and it’s not unusual that you might not grasp everything the first time around.

        • There are SO many variables! How many stones are present? Male dog or female dog? Have the stones moved into the penile urethra? Age of the pet. Comorbidities. Even the skill level and speed of the doctor performing the procedure. HOWEVER, the decision is not about cost, but reducing invasiveness. Thanks for reading, Dr. Randolph.

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