What are Kidney Stones?
Kidney stones don't typically present symptoms until they grow large, irritating the kidney ducts and potentially causing a serious infection or obstruction. Male cats and domestic Shorthairs are more likely to develop kidney stones than females and other breeds of cats.
The kidneys are responsible for filtering the blood, removing wastes such as mineral salts, urea, and toxins, and excreting these filtered wastes with water in the form of urine. Some of these wastes that are normally excreted by the kidneys aren't completely soluble and remain in the kidneys, forming crystals or renal calculi. Over time, these crystals can form stones, known as nephroliths, and cause a condition known as nephrolithiasis.
Symptoms of Kidney Stones in Cats
Small kidney stones often don't present symptoms and only become detected during a diagnostic test for another medical issue. Once kidney stones grow, however, they may cause the following symptoms:
- Loss of appetite
- Bloody urine
- Painful urination that is difficult to pass
- Abdominal pain
- Frequent urinary tract infection
- Frequent urination that only produces a small amount of urine
Causes of Kidney Stones in Cats
There are approximately ten different types of minerals that can form stones. Each type of kidney stone can be attributed to different causes. Some of these causes include:
- Underlying kidney infection
- Underlying urinary tract or bladder infection
- Increased calcium levels in blood and urine
- Supplements or diets that produce urine with a high alkaline pH
- Genetic defects
- Urinary retention
- Certain medications
- Certain concurrent illnesses or conditions
Diagnosis of Kidney Stones in Cats
The veterinarian will need to know the cat's complete health history, which will include a list of symptoms, any recent illnesses or urinary tract infections, and any recent changes to the cat's diet. The veterinarian will physically examine the cat and draw several labs, which will include a complete blood count, a biochemical profile, a urinalysis, and a bacterial urine culture. These tests can indicate any other organ systems that are being affected, other concurring illnesses or conditions, the presence of a urinary tract infection, and the type of bacteria that is present in the urine.
X-rays and ultrasounds will also be done. These tests can show the presence of stones in the kidneys. In order to correctly identify the stones, a procedure called extracorporeal shock wave lithotripsy (ESWL) may be performed. During this noninvasive procedure, shock waves will be used to break up the stones, allowing pieces to be removed from the urinary tract and identified. Identifying the minerals in the stones can help determine the best treatment for the cat.
Treatment of Kidney Stones in Cats
If the kidney stones aren't obstructing the flow of urine, the cat may be prescribed medication in order to dissolve the stones, allowing them to pass from the cat via the urine. The urine culture will identify any bacteria present in the urine and an appropriate antibiotic will be determined and prescribed in order to treat cats with urinary tract infections. Medication for pain will also be given to the cat in order to reduce their pain levels while treatment for the kidney stones occurs.
Cats who are dehydrated will need to be admitted to the hospital in order to receive fluid intravenously. The veterinarian will monitor the kidneys and heart during fluid therapy to ensure the fluids are being properly received by the body.
Stones that are obstructing the flow of urine will need to be removed promptly in order to prevent kidney failure from occurring. Extracorporeal shock wave lithotripsy (ESWL) is typically the first option used by veterinarians for the removal of kidney stones due to its noninvasive nature.
If the kidney stones are posing a medical emergency and ESWL isn't effective, surgery may be needed. During surgery, the veterinarian will make a small incision into the kidneys with the guidance of an ultrasound in order to remove the stones that are obstructing the flow of urine. The incision will be closed with sutures and the cat will remain in the hospital where it will be monitored. Surgery poses the risk of infection and of causing kidney damage, so it is only used when other treatment options aren't working.
Recovery of Kidney Stones in Cats
Kidney stones tend to recur, so routine monitoring via ultrasounds will be necessary. If the cat received surgery, a follow-up appointment will be necessary in order for the veterinarian to check the incision site for infection. The veterinarian may recommend dietary changes, such as feeding the cat a diet of 50 percent wet food. These dietary changes can help reduce the cat's risk of developing kidney stones. Ensuring the cat always has a fresh supply of water can reduce the risk of dehydration and stones forming again.