Kidney stones in dogs and cats are not commonly encountered but they are important to diagnose as they can have a significant impact on a pet’s life.
One of the main functions of the kidney is to filter waste products such as mineral salts and toxins. These products are then excreted in the urine. Under certain conditions these mineral salts can become stones that can form in the kidney, ureter, bladder and urethra.
Kidney stones are almost always (98%) caused by calcium oxalate.
Kidney stones: what to look out for
Pets often do not show symptoms in the early stages of the disease. However, if things progress, the stones may cause obstruction ultimately leading to kidney damage. Loose stones can move and become lodged in the ureter. This is often very painful and associated with symptoms of kidney disease.
Who is at higher risk?
Cats suffer from stones more often than dogs, with breeds such as Burmese, Persians and Himalayans at highest risk. In dogs, Yorkshire Terriers, Miniature Poodles, Lhasa Apsos and Dalmatians are at higher risk .
Kidney stones: common symptoms
- sudden onset of abdominal pain seen as pain when being picked up
- Blood in the urine
- Not eating
- Weight loss
Your vet will use x-rays and ultrasound to make a diagnosis. Cats with abnormal blood tests associated with kidney disease should have X-rays and ultrasound done of the kidneys and ureter to look for stones.
Treatment is largely dependent on the stage of disease, severity of symptoms and where the stones are located. Initially, patients are stabilised with intravenous fluids and medications to treat nausea and pain.
If the stones are in the kidney, this alone may be enough to stabilise and keep the patient comfortable. If symptoms reoccur, or if the stone is loose, surgical removal of the stone may be required. This should preferably be done by an experienced surgeon.
If the stone is lodged in the ureter and causing a blockage to urine flow, surgical intervention may be advised. In dogs, the stone can be removed from the ureter. In cats, the stone cannot safely be removed from the ureter, and a device (a SUB) to bypass the blockage in the ureter is inserted.
Unfortunately, kidney stones cannot usually be dissolved by special diets. These diets should still be considered to slow down any additional stone growth, and to maintain optimal kidney function. Also, using a laser to shatter the stone is often not successful. It may be used in very large dogs, but in smaller dogs and cats the process of shattering the stone causes too much damage to the ureter.
Any pet that has been diagnosed with kidney stones or has had surgery for the treatment stones should have kidney functions monitored on a regular basis. Follow-up X-rays and ultrasounds are also advised to monitor for the growth of existing stones or formation of new ones.
Early diagnosis is vital for successful treatment. And as pets often do not show symptoms in the early stages of disease, an annual health check with a complete physical examination is highly advised.
Article by Drs Morné de Wet & Esmaré van der Walt