Cystinuria (Australian Cattle Dog type) is an inherited disease affecting kidney function dogs. The SLC3A1 gene codes for a protein that allows the kidneys to transport cysteine and other amino acids from the urine. Normal kidneys reabsorb the amino acid cystine so that only small amounts pass into the urine, while dogs with mutations of both copies of the SLC3A1 gene fail to reabsorb cystine allowing large amounts to pass into the urine, hence the name cystinuria. Cystine can form crystals and/or stones in the urinary tract which can block the ureters or urethra and stop the normal flow of urine. Symptoms of disease include straining to urinate, frequent urination of small volumes or inability to urinate. In dogs, males and females are equally affected with excess cysteine in the urine, but obstruction of urine flow is more common in males due to differences in anatomy. Similar to other dominant diseases, affected dogs have variable onset and severity of clinical signs depending on the number of inherited copies of the cystinuria associated mutation. Dogs inheriting two copies of the mutation (one from each parent) have a higher concentration of cysteine in their urine than dogs with only one copy and tend to develop symptoms associated with cystinuria earlier. Dogs with cystinuria often have recurrent inflammation of the urinary tract and if not treated, urinary stones can cause urinary tract infections, kidney failure and even death.

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