Final answer:
Cystine crystals in urine may indicate urolithiasis or ethylene glycol toxicity, as well as inherited disorders like cystinuria or cystinosis, which can lead to kidney stones or tissue deposits that exacerbate renal issues.
Step-by-step explanation:
Observing cystine crystals in urine can be a normal or a pathogenic finding in dogs and cats, potentially indicating conditions such as urolithiasis (the formation of urinary tract stones) or ethylene glycol toxicity. In certain cases, the presence of these cystine crystals can be associated with an inherited disorder known as cystinuria in humans. This condition leads to high levels of cystine in urine and can result in the formation of kidney stones, experiencing symptoms such as colicky pain and hematuria.
Moreover, gout, a condition characterized by the accumulation of uric acid crystals in joints causing pain, can similarly result from excess purine consumption and is linked to the formation of kidney stones. Apart from cystinuria, metabolic disorders such as cystinosis, whereby cystine crystals deposit in various tissues and organs, also contribute to renal complications.