Cystinuria in Dogs and Cats: What Do We Know after Almost 200 Years?

SIMPLE SUMMARY: Cystinuria, as an inborn error of metabolism, is a problem with worldwide distribution and has been reported in various canine and feline breeds. Transepithelial transport of cystine is mediated by COLA transporter and the mutation in genes coding this transporter may cause cystinuria. Urolithiasis associated with typical clinical signs may be the clinical consequence of cystinuria. The mutation causing cystinuria and the mode of inheritance have been determined only in several canine breeds. This makes cystinuria difficult to control and gradually decreases its prevalence. In cats, cystinuria occurs only rarely. ABSTRACT: The purpose of this review is to summarize current knowledge on canine and feline cystinuria from available scientific reports. Cystinuria is an inherited metabolic defect characterized by abnormal intestinal and renal amino acid transport in which cystine and the dibasic amino acids ornithine, lysine, and arginine are involved (COLA). At a normal urine pH, ornithine, lysine, and arginine are soluble, but cysteine forms a dimer, cystine, which is relatively insoluble, resulting in crystal precipitation. Mutations in genes coding COLA transporter and the mode of inheritance were identified only in some canine breeds. Cystinuric dogs may form uroliths (mostly in lower urinary tract) which are associated with typical clinical symptoms. The prevalence of cystine urolithiasis is much higher in European countries (up to 14% according to the recent reports) when compared to North America (United States and Canada) where it is approximately 1–3%. Cystinuria may be diagnosed by the detection of cystine urolithiasis, cystine crystalluria, assessment of amino aciduria, or using genetic tests. The management of cystinuria is aimed at urolith removal or dissolution which may be reached by dietary changes or medical treatment. In dogs with androgen-dependent cystinuria, castration will help. In cats, cystinuria occurs less frequently in comparison with dogs.