Urinary bladder stones in dogs and cats can present substantial challenges to a veterinarian.
The most common problem occurs when we see a patient with recurrent urinary tract infections that seem to clear up, then relapse. Further investigation often uncovers bladder stones, also known as calculi (the singular is calculus), we can’t palpate (feel). Then we know that the foreign material, the stone, is harboring bacteria and reinfecting the urinary tract when antibiotic therapy is finished.
So, suppose your pet’s doctor finds stones by palpation or X-ray. What happens next?
Until about twenty years ago the only choice of treatment was surgery. The procedure for removing bladder stones is called cystotomy. The Latin prefix “cysto” refers to the bladder and “stoma” means to cut an opening. Cystotomy may be performed for many reasons including stone removal, tumor removal and exploration, among others.
Now, Prescription Diet s/d exists for removal of struvite stones in dogs and cats. Struvite is formed from ions of ammonium, magnesium and phosphate when the pH of the urine is high. Initially crystals form, then they coalesce to become small stones and eventually larger stones.
How does one know whether the stones his pet has are struvite? Two ways.
If you are really fortunate your pet will pass a stone which can then be sent to a laboratory for chemical analysis to determine its makeup. Even that, however, is not always simple. A stone may have a core of one or more ingredients and that core may be surrounded by outer layers of different ingredients.
The other way to find out stone composition is to perform a stone dissolution trial. Some stones are initiated by infection, so abnormal urine should always have a culture and sensitivity performed to determine whether infection is present, the nature of the infection and which antibiotics will work on the infection. During a dissolution trial antibiotics are administered continuously, either by mouth or Convenia injection, if the organism(s) is susceptible to Convenia.
To begin, radiographs (X-rays) are taken of the stone(s) in the bladder and each stone is measured. Prescription Diet s/d canned or dry food is fed exclusively. Even small amounts of treats or other foods may prevent stones from dissolving.
One month later a second radiograph is obtained. If stones are still present they are measured to determine whether they are diminishing in size. If not, the trial can be continued for another month. However, if the stones are not smaller after two months of faithfully feeding s/d exclusively, the stones are not likely to be of a struvite constitution, and therefore will not be dissolved.
On the other hand, if the calculi are getting smaller s/d can be fed indefinitely until they are completely gone.
Sometimes a stone will get smaller and smaller, then reach a certain size and stop dissolving. That indicates the core of the stone has a different constitution than the outside.
Insoluble cores must be removed surgically, as must stones that fail to respond to a dissolution trial.
A recent success story in stone dissolution is illustrated below. Puddles, shown at top, had urinary tract infections that would seem to clear, only to relapse a few weeks after antibiotic therapy was finished. After the second relapse we began to look for an underlying cause, and found the stones depicted below on the radiograph.
After 10 weeks of Prescription Diet s/d and five Convenia injections the stones were gone!
Puddles is no longer making puddles all over the house, is no longer uncomfortable, and is back to ruling the home like she used to.
Don’t you love a happy ending?