Uroretrohydropropulsion In Dogs


Any male dog can have urinary tract obstruction with stones.

Now, that’s a mouthful, even for someone who works with medical terms every day. Let’s break it down.

“Uro” refers to the urinary tract. “Retro” refers to something going backward. “Hydro” means water or another liquid will be used in the process. “Propulsion” refers to the movement of an object.

Uroretrohydropropulsion is a technique sometimes used in male dogs to relieve a blockage of the lower urinary tract caused by stones. The medical term for stones is calculi. The singular is calculus.

Dogs and cats usually form their stones in the urinary bladder, whereas people tend to form stones in their kidneys.

Male dogs have a bone in the penis called os penis or baculum. The os penis surrounds 80% of the circumference of the urethra, is two to three inches long, and sits at the end of the penis. From the bladder to the os penis, the urethra can expand dramatically to allow large volumes of urine and even large stones to pass. However, when calculi reach the portion of the urethra inside the bone, the urethra cannot expand, thus causing even small stones to become lodged.

If stones are of sufficient size, shape and number they can create a “logjam” effect, even stopping the flow of urine. That is a surgical emergency which, if not addressed quickly, can result in urinary bladder rupture.

Unlike female dogs, whose small stones can sometimes be removed by voiding urohydropropulsion, male dogs must have their stones removed surgically or by dissolution with diet.

The os penis bone in a dog's penis assists in reproduction. Credit Miller, Christenson and Evans, Anatomy of the dog.

When surgery is indicated it is preferable to remove the stones from the urinary bladder and not have to cut into the urethra. The urethra can be unforgiving after surgery. Scar tissue can form and restrict urine flow. Sutures in the urethra may fail, resulting in urine leakage under the skin as well as additional anesthesia and surgical time.

Thus, uroretrohydropropulsion was invented as a method of moving lodged stones back into the bladder, where they can be removed surgically with less risk of complications.

The procedure begins with catheterization of the urethra, passing the catheter only as far as the proximal (upstream) portion of the os penis. A large volume of balanced saline solution is injected into the catheter. Finger pressure is applied at the distal portion of the penis, thus preventing the solution from escaping and keeping flow in the proper direction. The goal is for the fluid to carry the stones back up the urethra, redepositing them in the bladder.

Multiple attempts may be required, and X-ray or ultrasound can be used to determine whether all of the stones have exited the urethra.

Uroretrohydropropulsionis not always successful. Some stones are too large to move and some may become embedded in the mucosa (lining) of the urethra. In such a case the surgeon has no choice but to make an incision into the penile urethra to remove the stones.

All stones will be chemically analyzed so that preventive measures can be taken to prevent future stones.

See you next week, Dr. Randolph.

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