Cystine - Blog Posts

Urine sediment from a 6 year-old, male-intact, Rottweiler.  The patient has a multi-year history of recurrent urinary tract infections.  He recently presented to his primary care veterinarian for being unable to urinate.  Radiographs showed no bladder stones, but a penile ultrasound showed many obstructing the urethra.  The dog was then referred for surgery to relieve the obstruction…

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The surgeons were kind enough to snag us some urine!  The urine was full of these hexagonal crystals….consistent with cystine crystals!  Yes, the amino acid cystine.  In addition, there were all shapes of sperms (see them swimming in the background!) along with many inflammatory cells and some bacteria.

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Diagnosis:  Cystine crystalluria.  This is a very rare occurrence in veterinary medicine!  Such patient’s often have a genetic defect in the metabolism or transport of cystine, allowing the amino acid to accumulate in blood.  Once it filters into urine, cystine will polymerize into crystals and sometimes form stones.  Cystine stones do not obstruct x-rays…hence they cannot be found on standard radiographs (termed radiolucent).  The patient is recovering well following surgery, and may require a special diet to help with his disease.