Bertie, a lovely 2 year old Pekingese, came in to us at the beginning of March because he was having difficulty passing urine and was feeling a bit under the weather. Bertie had a urine test that revealed blood and an alkaline pH, and an ultrasound scan which confirmed that there were some uroliths (bladder stones) present in his bladder.
The following day Bertie was admitted for an X-ray and an operation to remove the uroliths from his bladder. Bertie is now making a great recovery, although we are still waiting for the laboratory results that will tell us what type of uroliths he had.
Canine Urolithiasis explained
Urolithiasis is a disease caused by the presence and effects of excessive amounts of crystals and/or uroliths (stones) in the urinary tract . The disease is sometimes called by other names including cystitis, urethritis, urinary calculi and bladder stones. As with humans, these stones and crystals can form anywhere in the urinary tract of the dog, including the kidneys, ureters, urethra or most commonly, the bladder.
Bladder crystals and stones are formed by minerals in the urine. Over time, the minerals bond together forming crystals and once these first crystals are present in the right conditions they can be built up into stones that sometimes reach 3″ to 4″ in diameter.
These crystals and stones irritate the lining of the urinary tract, causing changes in the lining, blood in the urine, and pain. In some cases the crystals or stones will block or partially block the flow or urine, making urination painful or impossible.
Types of urolithiasis in dogs
There are several different types of crystals and bladder stones that can occur in dogs. Struvite are composed of magnesium ammonium phosphate while others are made of calcium oxalate, calcium phosphate, cystine, ammonium urate, or other compounds (some stones can actually be a combination of these). Each type of stone has its own different peculiarities as to which breed is most often affected and what factors affect the formation.
How urolithiasis occurs
There is no single cause of canine urolithiasis, but there are a number of important factors that may have an impact.
Genetics: The physiology of some dogs causes their bodies to produce higher levels of the substances that form the crystals; these are then excreted or formed in the urine.
Breed: Miniature Schnauzers, Pugs, Pekingese, Yorkshire Terriers, Dachshunds, Dalmatians and Labradors are some of the more commonly affected breeds.
Gender: Crystals and stones occur in both male and female dogs but, because the urethra of the male is longer and narrower than the female’s, urethral obstruction is more common in males.
High mineral intake: The higher the urine concentration of minerals that make up the stones, the higher the risk that stones will form.
Urine pH: The acidity or alkalinity of the urine can influence the formation of crystals and stones. Some crystals, such as struvite, form in alkaline urine, whereas others form in acidic urine. The urine pH is largely influenced by diet.
Bacterial Infections: Bacterial infections of the bladder can play the major role in struvite stone formation. They make the urine more alkaline which enhances the formation of struvite crystals and the by-products of bacterial metabolism may also enhance crystal formation.
Holding urine for long periods: dogs that have been confined or have a lack of regular exercise and are unable to pass urine on a regular basis are more likely to develop this disease
Low water intake: Dogs that do not drink enough may also be more likely to develop this disease
Diet: High levels of some minerals in the diet, such as magnesium, phosphorus, and calcium, have been directly linked to canine urinary bladder stone formation. A diet with excess protein can also contribute to stone formation. Diet can also influence the acidity or alkalinity of the urine.
Signs and symptoms of urolithiasis
A dog with urolithiasis will exhibit some or all of the following symptoms:
- Frequent urination (often in unusual places)
- Bloody urine
- Dribbling urine
- Straining to urinate
- Loss of appetite
- Vomiting and pain
How urolithiasis is diagnosed
The vet may perform some or all of these tests
- Urinalysis, to determine the pH and concentration of the urine, if there is any blood or bacteria present and the types of crystals that may be present.
- Abdominal palpation, to feel stones present in the urinary bladder
- Ultrasound and/or X-Ray to see if stones are present and their location in the urinary tract (some uroliths do not show up on normal X-rays and this can help the vet narrow down the type of urolith that is present).
- Laboratory analysis of the uroliths; this will tell the vet exactly what type of urolith the dog has and thereful aid in deciding what treatment and preventative measures are necessary.
How urolithiasis is treated
Dietary changes: Depending on the type of crystals or stones your pet has, your vet may recommend a prescription diet for you dog that will either dissolve crystals that are present in the urine or prevent crystals from reforming.
Increase water intake: This may be done by feeding more tinned food or making water more exciting for the dog i.e. By using water fountains or flavouring the water with very dilute broth.
Medication: This may be used to treat any bacterial infections that are present.
Surgery: The two main types of surgery that are performed are
- Crystals can sometimes be removed using urohydropropulsion. The dog is anaesthetised and a urinary catheter is placed. Through the catheter, the bladder is filled with a sterile saline solution and the crystals may be flushed out of the urinary tract. This method can only be used with crystals or stones that are small enough to be passed.
- Stones that cannot be passed through the urinary tract must be surgically removed during a procedure called a Cystotomy. The dog will be anaesthetised and the surgeon will make an incision in the dog’s abdomen and then into the bladder; the stones are then removed and the bladder is flushed with a sterile saline solution, before being sutured closed again.