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Cat's Kidney Stones a Big Problem with a Tiny Solution


Pet Column for the week of March 3, 2014

Related information:

Related site - Small Animal Surgery at the Veterinary Teaching Hospital

[Dr. Heidi Phillips]
Dr. Heidi Phillips performs urogenital and microsurgery at the University of Illinois Veterinary Teaching Hospital in Urbana.

Office of Public Engagement
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Urbana, Illinois 61802
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Sarah Netherton
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Source - Dr. Heidi Phillips
At more than 14 years old, Sue was already a very lucky cat. She had beaten a number of serious health problems even before her owners brought her to the University of Illinois Veterinary Teaching Hospital in Urbana in the fall of 2013 for treatment of a cancerous growth on her chest. Sue's luck held out when she had the good fortune to be a patient of Dr. Heidi Phillips, one of a small number of veterinary surgeons who perform urogenital and microsurgery.

Veterinary specialists at the hospital took X-rays of Sue's chest and performed an abdominal ultrasound in order to find the source of her spreading cancer. During these examinations, they discovered that Sue also had a partially obstructed ureter, the tube that carries urine from the kidney to the bladder, on the left side.

To treat Sue's cancer, surgeons removed the mass on her chest and veterinary oncologists prescribed rounds of chemotherapy. When Sue came for a re-check ultrasound, doctors found that Sue's right ureter had also developed a kidney stone—a hardening of calcium oxalate crystals that originate in the kidney. The examination also showed that Sue's renal pelvis (the part of the kidney that collects the urine) and the ureter itself were expanding.

“With the existing obstruction of her left ureter and her right ureter starting to block, Sue's kidney stones needed to be surgically removed,” says Dr. Phillips.

According to Dr. Phillips, a blocked ureter can be a common problem in cats. Owners may notice such signs as vomiting, abdominal pain, food refusal, straining to urinate, and blood in the urine, though these are also indicators of other problems.

When a veterinarian suspects a blocked ureter, an abdominal ultrasound or computed tomography (CT) imaging can be performed. Blockages can be seen on X-rays as well as via ultrasound.

“The renal pelvis and width of the ureters can be measured with ultrasound,” says Dr. Phillips. “Normally, the interior width of a cat’s ureter is less than half a millimeter, so a stone or other object larger than this will cause an obstruction.”

For comparison, the wire used to make the standard paper clip is about one millimeter in diameter, so the width of the ureter is less than half of that.

In Sue's case, the blockages were midway to higher up in her ureters, closer to the kidneys than to the bladder. Dr. Phillips performed a surgery, called an “ureterotomy,” that requires special forceps and scissors and is performed using an operating microscope to magnify the area by at least ten times. The suture material used for microsurgeries is also on a much smaller scale than what is used for conventional surgeries.

“The area directly over the stone is cut and the stone is then removed,” explains Dr. Phillips. “The ureter is flushed to ensure there are no clots, and then the area is carefully closed with the aid of the microscope.”

Post-operative care includes managing an animal in kidney failure and feeding a low-protein diet. Providing cats with plenty of water, feeding wet food, and giving dry food only as a treat can reduce the chance of calcium oxalate stone formation.

According to Dr. Phillips, cats can do very well after an ureterotomy. As long as any kidney problems are properly managed, these patients rarely have blocked ureters again.

Sue did very well after her surgery. After performing two computed tomography scans, doctors did not find cancer anywhere else in her body. To date, the cancer in the skin which doctors thought was spreading has not recurred. Dr. Phillips said Sue has regular check-ups at the Veterinary Teaching Hospital, and she is energetic and has a good quality of life. Sue's owners have consulted a veterinary nutritionist to help Sue increase her weight.

If you have questions about cats with blocked ureters, speak with your local veterinarian.