Cystine Urolithiasis (Bladder Stones) in Dogs

Overview of Cystine Urolithiasis in Dogs

Cystine uroliths, also referred to as calculi, are stones within the urinary tract composed of the amino acid cystine, a breakdown product of proteins. Cystine urolithiasis is most common in male dogs with an average age of onset of three to five years. It is most commonly seen in the dachshund, English bulldog, and Newfoundland. Cystinuria is an inherited trait in Newfoundland dogs. Clinical symptoms depend on size and number of uroliths as well as their location within the urinary tract. Some affected animals may have no clinical symptoms.

The exact mechanism of cystine uroliths formation is unknown. Cystinuria (presence of cystine in the urine) is a predisposing factor. Cystinuria is an inborn error of metabolism characterized by defective transport of cystine by the tubular cells of the kidneys.

What to Watch For

Signs of Cystine Urolithiasis in Dogs may include:

Affected animals may be extremely ill if they have associated kidney failure or infection.

Diagnosis of Cystine Urolithiasis in Dogs

Treatment of Cystine Urolithiasis in Dogs

Depending on the size and location of the stones, treatment may be medical or surgical. Surgery may be indicated if urethral obstruction is present.

If urethral obstruction is not present, dissolving the stones may be feasible. A low protein diet combined with the drug 2-mercaptopropionyl glycine (2-MPG or Thiola) has been used to reduce the urinary excretion of cystine and to dissolve cystine stones. There is little experience using 2-MPG in cats.

Additional treatment may include:

Home Care and Prevention

Strict compliance is necessary if your dog is on a special diet and is receiving medication to dissolve cystine stones. Return for follow up examinations and tests as recommended by your veterinarian.

Without preventive care, cystine uroliths tend to recur within 6-12 months of removal or dissolution. Cystine stones can recur even when medical treatment and dietary management are strictly followed.