Cystinuria is a type of kidney disease characterized by defective reabsorption of cystine and other basic amino acids in the kidneys resulting in an abnormally high urinary levels of cystine, lysine, arginine, and ornithine. After entering the kidneys, most cystine normally dissolves and goes back into the bloodstream, but individuals with cystinuria have a genetic defect that interferes with this process. As a result, cystine builds up in the urine and forms crystals or stones, which may get stuck in the kidneys, ureters, or bladder. Not all dogs with cystinuria develop urolithiasis. Originally discovered in Basenji dogs, it is now recognized in more than 60 breeds of dogs. A severe form has been described in the Newfoundland.2 Dachshunds are the most common breed to develop cystine uroliths. Cystine uroliths are usually small, smooth, yellow brown to yellow green.
Cystine uroliths can be surgically removed or medically dissolved. Feeding a protein restricted diet low in methionine and increasing water intake will dilute the crystals, but salt should not be administered as increased sodium may increase urine cystine excretion. Increasing urine pH > 7.5 will increase solubility of crystals. Potassium citrate is preferred over sodium bicarbonate due to sodium's effect on increasing urine cystine. D-penicillamine changes cystine to more soluble form. D-penicillamine delays wound healing and should be avoided immediately after surgery if calculi are surgically removed. Alpha-mercaptopropionylglycine (MPG) has fewer side effects and appears to be more effective than D-penicillamine, but is not approved yet for use in dogs.
Cystinuria was originally discovered in Basenji dogs
- Yolande M. Bishop. The Veterinary Formulary
- Jiro J. Kaneko, John W. Harvey, Michael Bruss. Clinical Biochemistry of Domestic Animals