Ureter Stones in Cats

Often the condition goes unnoticed until the affected kidney begins to fail.The condition is found more commonly in middle-aged to older cats. If a ureter becomes fully blocked, the situation can be life-threatening and immediate veterinary attention is required. 

When minerals or calcium build up to the point of overwhelming the kidneys, stones may begin to form. This process is called nephrolithiasis. These stones can move from the kidneys, through the ureters (thin ducts), and down to the bladder. Because the ureters are so narrow and have thick, muscular walls, stones can often get lodged within them and cause serious problems for the cat. The stones are made of calcium oxalate over 90 percent of the time, but can also be formed of ammonium biurate. Calcification of blood clots may also form stones. 

While symptoms will eventually occur once stones have grown to dangerous sizes, usually this problem is discovered during treatments or ultrasounds for other conditions. Symptoms are as follows:

• Kidney failure
• Hematuria (blood in urine)
• Abdominal pain
• Anorexia (weight loss from food abstinence)
• Polyuria (frequent urination)
• Dehydration
• Vomiting
• Lethargy
• Inability to urinate

Please note if your cat is unable to urinate it is a medical emergency requiring immediate professional assistance.

Ureteral stones are produced in the kidneys, so most causes are associated with the function of the kidney. All known causes are listed below.

• Defective metabolism
• Diet (acidic, dry foods)
• Prolonged dehydration (even if mild)
• Excessive calcium processed from the kidneys
• Genetic predisposition (found especially in Persian, British Shorthair, Ragdoll, Scottish Fold and Burmese cat breeds)
• Vitamin B6 deficiency
• Tumor in the parathyroid gland
• Cancer
• Liver disease (in the case of ammonium biurate stones)

Upon arrival to the clinic or hospital, the veterinarian will request your cat's medical history and begin a complete physical examination, palpating (feeling) the kidneys to check for size difference or tenderness. The unaffected kidney can grow larger to accommodate the blocked kidney, which will shrink and cease to function. 

X-rays will be requested to confirm both the presence and the location of stones. An ultrasound of the urinary tract may be needed to show any distention. A nuclear scintigraphy scan may be needed to test if the kidney is functional. Blood tests along with a complete blood count may be needed if cancer is suspected. Urinalysis will be requested to test for and identify bacteria that are causing infection. Computed tomography (CT scan) may be used to find the number of stones and their location. 

If X-ray and ultrasound results are inconclusive, either an Excretory Urography (EU) or an Ultrasound-Guided Antegrade Pyelography (AP) may be performed. Both require the use of general anesthesia.

Generally, if the situation is not an emergency, nonsurgical options will be attempted first. Due to the high risk of kidney and ureter surgery, inactive stones are often not treated at all but instead are monitored for potentially dangerous changes every few months. Typical treatments include:

Aggressive Fluid Therapy 

The cat will be given fluids intravenously to flush out the kidneys and ureters, with the goal of pushing stones to the bladder. This will continue for 12-24 hours with the cat being given X-rays periodically to see if the stones have moved. Continuous monitoring throughout the procedure will take place to ensure the cat does not collect fluid in its lungs.

Removal Surgery 

More often than not, surgery will be needed to rectify the situation. This surgery is quite complicated due to the small size of the ureters. Fine sutures and an operating microscope should be used to perform the procedure. Once the stone is removed, the ureters will be flushed to ensure fluids are passing from the kidneys to the bladder. Sometimes an additional incision in the bladder is needed to verify the flow. An IV will be administered after the surgery. 

Stenting 

Sometimes the affected ureter can be bypassed with a permanent tube. This surgery still carries risks but it has a very high success rate. Currently, it is only offered in a few places.

Subcutaneous Bypass Device 

A tube within a tube surrounded in mesh can also be implanted from the kidney. The mesh allows urine to pass while the inner tube collects the stones. The surgery is still relatively new but the prognoses have been good.

Extracorporeal Shock-Wave Lithotripsy 

Shockwaves are used to pulverize stones while the surgeon monitors the procedure with an ultrasound. This is more difficult in cats due to their small size. Stones must be large for the treatment to be effective.

Nephrectomy 

In cases of cancer or other serious kidney failure a nephrectomy (kidney removal) may be needed. This surgery is very high risk with mortality a real possibility.

Pain Medication 

After any of these procedures, strong pain medication such as Buprenorphine or Fentanyl may be prescribed. These prescriptions generally run for 2 weeks post surgery.

Antibiotics 

If infection is found during the diagnosis, or if one develops post surgery, antibiotics will be prescribed to fight the bacteria. Duration of antibiotic therapy is usually 2-4 weeks.

If your cat has undergone surgery of any kind, it is important to check the incision site daily for signs of infection. Confirm that your cat is properly urinating once at home. A bowel movement should be seen within 4-5 days. Post surgery complications can become life threatening so this close monitoring is imperative.

Aromatic, wet food should be given to the cat to entice eating and to present more fluids into the digestive system. At first the food may need to be warmed, and you may have to hand-feed your cat. Appetite stimulants may be prescribed, and if the cat still refuses to eat, a feeding tube may be necessary for a time. Once the stones have been analyzed, your vet may recommend a specialized diet to prevent the reformation of ureter stones. Present fresh water often to your cat to encourage more drinking.

Offer lots of affection to your cat in this recovery period. It can help to lessen the cat's stress and promote healing. If the surgery heals, the prognosis is generally quite good, even if the cat continues to have kidney disease. The cat should be brought to the vet every 3 months for X-rays to verify stones are not reforming and to identify a course of action if they are.