1116. Another edited version of struvite bladder stones to the editor

What are bladder stones?

Bladder stones or uroliths are common in domesticated animals. There are many types of bladder stones depending on their composition.

Struvite bladder stones

Struvite bladder stones are most commonly seen in canine cases at Toa Payoh Vets and this article is to educate dog owners regarding their diagnosis and treatment. They can be formed anywhere along the urinary tract in the kidneys, the urethra and the bladder when the urine is supersaturated with magnesium, ammonium and phosphate (MAP). MAP supersaturation may be associated with several factors, including urinary tract infections, alkaline urine, genetic predisposition and diet. Breeds usually affected by struvite bladder stones include the Miniature Schnauzer, Shih Tzu, Bichon Frise, Miniature Poodle, Cocker Spaniel and Lhasa Apso, but any breed can be affected. Female dogs are said to form approximately 85% of bladder stone cases.

Symptoms of bladder stones

Some dogs may not show clinical signs such as blood in the urine, difficulty in urination, or inability to urinate, until much later in the disease with severity of signs depending on the location, size, and number of uroliths formed. Your vet will take a comprehensive history to determine the start and severity of the disease. Physical examination includes bladder palpation to feel the crepitus (sounds of gas and stones rubbing against each other) inside the bladder or the solid stones if they are large.

Diagnosis

Urine analysis is the most useful and a sterile sample is taken by catheterisation or cystocentesis (straight from the bladder). The pH of your dog’s urine will also give a good idea of the nature of the stone. The urine sample will show the presence of bacteria, which is usually cultured to find out the type of bacteria causing the urinary tract infection. Antibiotic sensitivity tests are needed to figure out what appropriate antibiotics can be prescribed.

Uroliths need to be of a certain size before they are evident. The number and size of urinary stones seen in the x-ray may not correlate with the severity of clinical signs. A radiograph is highly recommended to find out the number and size of stones and where they are located prior to surgical removal, if surgery is required. In spite of all the tests above, the composition of the actual stone cannot be determined unless a stone sample (from the surgery or that has been urinated out) is sent for analysis.

Treatment

There are two types of treatment for struvite bladder stones; surgery or medical dissolution of the stones. The benefits of surgery include a shorter recovery period and the ability to identify the actual type of stone involved. Surgery is needed if the stones are too large as they may not dissolve by medical dissolution. Disadvantages of surgery are that it is more invasive and there are risks of death during or post operation, associated with general anaesthesia in a sick and/or older dog.

Medical dissolution takes a much longer time (about three months on average) to take effect and large stones may not dissolve at all. It revolves around three main concepts – to acidify urine, reduce the intake of MAP such that it does not saturate in the urine and dilute urine so struvite crystals do not have a chance to form. Affected dogs are usually prescribed calculytic diets and appropriate antibiotics to treat the bacterial infections. No other food or treats should be given and plenty of water drinking should be encouraged.

Most importantly, your dog’s health should be reviewed every three months with urine tests and X-rays to ensure that no new stones or crystals are formed. Be alert as to the urination pattern of your older dog and seek veterinary advice promptly if there are signs of blood in the urine, urinary difficulty or inability to pee.
 
Dr Sing Kong Yuen

BVMS (Glasgow), MRCVS

Toa Payoh Vets

 

Sep 25, 2012. Edited version for the editor

My opinion. A technical report. Quite a boring article without pictures for the layman but has most of the important facts.