Cystinuria - CYN



CYN is a disease affecting the kidneys; it is caused by a defect in the transport of the amino acid cystine.

The disease prevents affected dogs from properly reabsorbing cystine which leads to unusually high levels of cystine in urine and results in the formation of cystine crystals. Ultimately cystine crystals lead to the formation of cystine calculi (stones) in the kidney and/or bladder. These stones can lead to urinary blockage, particularly in males. Without early treatment CYN can cause kidney failure, bladder rupture and death. CYN symptoms can be detected in urine as early as a week of age, but needs to be treated as soon as possible to prevent further health problems.

Severity - 5

CYN has a high ‘degree of severity’, it greatly decreases the quality of life for you and your dog due to the high risk of infec-tion and the shortened lifespan of the affected dog.


The major symptoms of cystinuria are:
- Difficult urination / Inability to urinate
- Blood in urine.

Dogs that show signs of a possible urinary tract infection should be tested, particularly if they are repeating symptoms. Male dogs have a narrower urethra than females and so any suspicions in males should be tested immediately as they are more likely to suffer complete blockage, leading to the rupture of the bladder and/or kidney failure, and eventually death.

While the disease is able to be managed with constant treatment and in severe cases repeated surgeries, Cystinuria can lead to ongoing medical issues and can greatly decrease the quality of life for you and your dog.

Genetic Testing

Animal Network provides a DNA test that determines the genetic predisposition to CYN.

Cystinuria is an autosomal recessive disease. A recessive phenotype (trait or disease) will only be expressed when two copies of the recessive gene variant are present. A direct gene test can detect whether a dog is clear, carrier or is affected by the disease.

A dog with two copies of the recessive gene variant is affected, they will express the phenotype and will pass a copy of the gene variant onto their offspring 100% of the time. A dog with one copy of the recessive gene variant is a carrier, they do not express the phenotype themselves, however they are will pass the gene variant onto their offspring 50% of the time. A dog that has does not have any copies of the recessive gene variant is clear, and will never produce affected offspring.

For an explanation of possible genetic status of offspring please refer to our fact sheet on Breeding strategies. ORDER A TEST

Breeds Affected

Labrador Retriever

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