Bladder stones are also known as urinary bladder calculi or uroliths, and can occur in many companion animals. Their presence in a cat’s bladder causes local irritation to the bladder wall. They can then pass through to the urethra and lodge there, resulting in a life-threatening situation where the cat can no longer urinate. It is important to understand how to recognise the early signs of bladder stones as well as how to prevent them.
Bladder stones form when there is a particular environment created in the cat’s urine. There are a few different varieties that can form and they rely on the appropriate pH (acidity), concentration, chemical components as well as the presence of infection. Some breeds are more predisposed to forming stones and often cats fed cheaper supermarket brand foods are more likely to have trouble with bladder stones.
The most common sort of bladder stone seen in the cat is made up of struvite crystals. For these to form there needs to be strongly concentrated and alkaline urine as well as higher levels of magnesium, ammonium and phosphate. The struvite crystals start to form and then start to clump together to form stones. Another bladder stone seen in cats is calcium oxalate. These are more likely to form in acidic urine and be seen with diets high in calcium, protein, sodium, vitamin D and oxalate.
Early symptoms of bladder stones are usually bleeding and visible discomfort. If the stones lodge in the urethra then the bladder can become blocked, resulting in a build up of urine which puts pressure on the kidneys, and if left untreated can result in a ruptured bladder.
After gaining a thorough history the vet will physically examine your cat. Sometimes a stone can be felt when the bladder is palpated, but more often a painful or over-distended bladder is detected. To confirm the presence of a stone, often imaging is required such as an abdominal ultrasound or an x-ray. A urine sample is useful to assess the pH, concentration, presence of infection and crystals that help to increase the suspicion of a stone being present. A blood test may be recommended to assess your cat’s kidney health as well as the levels of calcium and electrolytes. It is also advisable to have a blood test to ensure your cat would be a suitable candidate for surgery if required.
Once a stone has formed it is very difficult for them to dissolve, in particular the calcium oxalate ones. Surgery is usually required to remove them from the bladder. Sometimes, dietary changes, treatment of any infections with antibiotics and an increase in water intake can help to dissolve them, but more often than not these are put in place to prevent a recurrence of crystals and stones. Anti-inflammatories are often prescribed to reduce the irritation and discomfort of the bladder wall.
Ensuring your cat drinks water frequently or alternatively feeding them more wet food will assist in preventing bladder stones. Additionally, high quality and prescription foods may dissolve some crystals and ensure an optimal pH.
If a bladder stone is detected and removed surgically then it is important that it gets sent off for assessment to determine what sort of bladder stone it is. This helps in guiding treatment to put in place preventative measures to minimise the chance of this particular stone forming again.