Canine Bladder Stones: Diagnosis and Treatment

Dr. Marty Greer, DVM joins host Laura Reeves for a deep dive on bladder stones in dogs, how to diagnose and treat them. The following information is provided by Dr. Greer.

Bladder stones are the quintessential “which came first, the chicken or the egg” question. By this, we mean that a dog can have a bladder symptoms that are caused by a bladder stone, or the bladder infection can cause bladder stones to form. Which then becomes a vicious cycle.

There are two basic types of bladder stones – the first, struvite stones associated with a bladder infection or second, any of the following other bladder stones, caused by a metabolic disturbance that causes a stone to form in the urinary tract.

How do bladder infections cause bladder stones? An undiagnosed, under-treated or recurrent bladder infection can lead to the development of struvite bladder stones. This is the most common type of bladder stone. Or another type of stone can cause irritation to the bladder which can cause a stone to form that is partly any of the types of stone below combined with a struvite stone. These form like a pearl in an oyster – the irritation of the infection or other stone type can cause a struvite coating on an existing bladder stone.

Many metabolic stones are associated with a particular breed or disease condition causing minerals to deposit in the bladder, forming stones. These metabolic stones form with long term supersaturated minerals in the urine. With time, the crystals form which develop into a bladder stone. Other factors are the pH of the urine, inhibitors and promotors of stone formation, and macrocrystalline matrix. If something like suture is in the bladder, this can also allow a stone to form.

Fortunately, most stones in the urinary tract are in the bladder itself, where they are accessible surgically. Stones in the kidney or ureter (tube from the kidney to the bladder) are not easily managed surgically or by physical removal. Stones that form in the bladder and pack together like sand in a funnel or slip from the bladder into the urethra (tube from the bladder to the outside of the body) cause urinary obstruction. This is a true medical emergency, more common in males that females due to the length and shape of the urethra, the tube from the bladder to the outside.

Males have a design flaw – their urethra is more narrow and curved, causing a greater likelihood of urinary obstruction. On the other hand, females have a design flaw, a shorter wider urethra just below the rectum that allows bacteria to ascend into the bladder, increasing the risk that a female will have a bladder infection. That infection can often lead to the formation of struvite stones.

Symptoms

Symptoms of bladder disease can be virtually non-existent to severe. The symptoms can vary:

1. No signs or very subtle signs of discomfort or urinary accidents.
2. Signs of blood in the urine (often not noted until there is snow on the ground or when the urine is wiped up and blood is seen on a white towel), straining to urinate, frequency of urination, inappropriate urination, +/- fever, pain, and/or urinary incontinence. Dogs are rarely “sick” with a bladder infection – they eat, drink, and act normally other than increased trips outside or urinary accidents on the floor.
3. If obstructed, there will be abdominal pain, vocalizing, vomiting, dehydration, depression, heartbeat irregularities, bladder distension, in advanced cases, bladder rupture, collapse and death.
4. Blood work can show elevated BUN and creatinine, kidney values if obstructed.
5. Blood work may show elevated calcium if calcium oxalate stones are present.
6. Blood work may show liver dysfunction in patients with urate stones.

Below is a table showing the different types of bladder stones, comparing the composition, cause, prevention and treatment options.

The above table is a summary of information published on www.veterinaryinformationnetwork.com. Thanks to this author Kari Rothrock DVM.

Diagnosis

1. Symptoms are noted.
2. Urinalysis: crystals seen on microscopic evaluation of the urine, bacteria, white blood cells, and white blood cells seen under the microscope.
3. Culture – to identify the causative bacteria.
4. X-rays – seeing stones in the bladder, kidney, ureter or urethra. May require contrast x-rays.
5. Ultrasound – stones or gritty material seen blocking the ultrasound beam on ultrasound. This may be described as a “snow globe”.
6. Stone analysis – essential to know the cause and how to try to prevent formation of future stones.
7. Cystoscopy – when an endoscope is passed into the bladder to look for stones. Removal may be achieved at this procedure.

Physical Removal of stones: there are several techniques available to remove stones from the urinary tract.

1. Surgical removal – is a procedure available at most small animal veterinary clinics with basic surgical availability. If an obstruction is present, immediate surgical intervention is essential.
2. Cystoscopic retrieval – requires an endoscope and special baskets to retrieve stones from the urethra and/or bladder.
3. Voiding urohydropropulsion – With sedation or anesthesia, the bladder is catheterized, filled with fluids multiple times, and with pressure on the bladder, efforts to push the stones out through the urethra is attempted. This works best in small dogs with small stones.
4. Extracorporeal Shock Wave Lithotripsy (ESWL) – This involves using a shock wave to a patient immersed in a water bath. Bladder stones may move too much for this to have a successful outcome so is better suited for stones in the kidney or ureter.
5. Laser lithotripsy – This involves using a laser to fragment them, then the fragments are removed. This works better in female than male dogs. Small dogs and large bladder stones may not lend themselves to this treatment option.
6. Retrograde Urohydropropulsion (RU) – this involves flushing stones from the urethra back into the bladder for removal. In general, the patient will require sedation or anesthesia, followed by removal of some urine to relieve the pressure on the bladder.

Other than surgical removal, the others are usually only available at larger referral centers or veterinary schools.

Dissolution – is a process by which bladder or kidney stones can be dissolved using special diets, drugs, and or antibiotics. Not all stone types will dissolve. And not all dissolvable stones will dissolve safely. If the dog has an obstruction and cannot urinate, immediate physical removal of the stones is essential as urinary obstructions are life-threatening. Not all dogs will eat the diet required to dissolve the stones. Not all owners are willing or able to administer the medications and diets necessary to dissolve the stones. Frequent monitoring of the size and location of the stone is essential to safely allow stones to dissolve. The required diets are prescription diets, and the medications are also prescription drugs. Care in selecting the correct food and medication is required, thus the reason for prescriptions from the pet’s veterinarian.

Prevention can often be successful. Again, this requires that the owner(s) of the dog take great care to provide plenty of fresh water frequently, let the dog out to urinate frequently, and administer medication and food without “cheating”. Owners may also need to check weekly urine samples to assess the urine pH for early adjustments in medication and food to prevent recurrences.

As a result, a mutual treatment plan with the pet owners and their veterinary team is essential for a successful outcome.