Aula 4 - Urólito de urato

Summary

This informative presentation covers the identification and treatment of urate crystals (urólitos de urato) in dogs and cats, focusing on breed predispositions, genetic factors, and metabolic processes. The speaker explains how purine metabolism leads to the formation of urate crystals and discusses common breeds affected, such as Bulldogs and Dalmatians. The video outlines diagnostic techniques, including laboratory and imaging tests, and emphasizes the importance of genetic testing. Treatment options, such as dietary changes, hydration, and medication, are explored, alongside prevention strategies. The presentation concludes with practical advice for managing this condition in pets.

Takeaways

• 😀 Urate uroliths are formed from purine metabolism, specifically from compounds like uric acid and ammonium urate, and are common in both dogs and cats.
• 😀 Certain dog breeds, like Bulldogs and Dalmatians, are genetically predisposed to urate stones due to a mutation that affects uric acid metabolism, leading to higher concentrations of uric acid in urine.
• 😀 Urate uroliths can also form in dogs treated with allopurinol, which inhibits xanthine oxidase, increasing xanthine concentration and leading to xanthine stones, another type of urate-related lithiasis.
• 😀 In cats, urate stones are less understood in terms of genetic predisposition, though some felines with hepatic vascular anomalies (shunts) may develop ammonium urate crystals.
• 😀 The most common type of urate stone in cats is ammonium urate, and it often occurs in castrated cats aged 4-7 years, typically in the bladder and urethra.
• 😀 Ammonium urate crystal formation in cats may be linked to dietary factors, including higher intake of DNA/RNA-rich tissues like organ meats, leading to supersaturation of purine metabolites in the urine.
• 😀 Hepatic vascular anomalies (such as shunts) can contribute to urate stone formation due to impaired uric acid conversion, causing higher levels of ammonia and uric acid, which promotes crystal formation.
• 😀 Diagnosis of urate uroliths requires a combination of clinical evaluation, laboratory tests (urine density and pH), and imaging (ultrasound, X-ray, and possibly uretrocystography).
• 😀 Treatment involves addressing the underlying cause, ensuring adequate water intake and urination, and dietary adjustments to reduce purine intake, particularly in affected dogs and cats.
• 😀 Surgery is often required to remove urate stones as they are difficult to dissolve; non-invasive procedures like cystotomy may be used when appropriate.

Q & A

What are urate uroliths, and how are they formed in animals?

Urate uroliths are kidney stones formed from the metabolism of purines, which are catabolites derived from DNA and RNA. They include compounds such as uric acid, ammonium urate, allantoine, and xanthine. These stones are primarily composed of ammonium urate, which is insoluble in urine.

Which dog breeds are more predisposed to urate uroliths, and why?

Breeds like the Bulldog and Dalmatian are more predisposed to urate uroliths due to a genetic mutation affecting the transport of uric acid. This mutation causes a decreased conversion of uric acid to allantoine, leading to a higher concentration of insoluble uric acid in the urine, which promotes stone formation.

What is the role of uricase in the formation of urate uroliths?

Uricase is an enzyme that converts uric acid into allantoine, which is soluble in urine. In certain dog breeds with genetic mutations, the action of uricase is impaired, resulting in a decreased formation of allantoine and an increased concentration of insoluble uric acid, which contributes to urate urolith formation.

How does allopurinol influence urate urolith formation?

Allopurinol inhibits xanthine oxidase, which reduces the formation of uric acid and increases the concentration of xanthine. Xanthine, like uric acid, is insoluble in urine, and its accumulation can lead to the formation of xanthine stones, which is a potential side effect of allopurinol treatment.

What is the role of genetic defects in xanthine urolith formation?

Xanthine uroliths can form due to genetic defects in xanthine metabolism, known as hereditary xanthinuria. This genetic condition affects the conversion of purines into uric acid, resulting in elevated xanthine levels in the urine, which can lead to stone formation.

What is the connection between hepatic vascular anomalies and urate uroliths?

Hepatic vascular anomalies, such as shunts, can cause inefficient purine metabolism, leading to a higher concentration of ammonium urate crystals in the urine. This condition is linked to the formation of urate uroliths in animals, as impaired liver function affects the conversion of uric acid to allantoine.

How common are urate uroliths in cats, and what is their main cause?

Urate uroliths are the third most common type of urinary stones in cats, with ammonium urate being the most prevalent form. While there is no clear genetic predisposition in cats, dietary factors, such as high levels of purines from organ meats, may contribute to the formation of these stones.

What diagnostic methods are used to detect urate uroliths?

Diagnosis involves clinical evaluation, laboratory tests, and imaging techniques. Urinalysis can reveal the presence of ammonium urate crystals, while imaging methods like ultrasound and X-rays help confirm the presence of stones and evaluate underlying conditions, such as hepatic vascular anomalies.

What are the challenges in treating urate uroliths in animals?

The main challenge in treating urate uroliths is that they are difficult to dissolve. Treatment often requires surgical removal, as non-invasive methods such as dietary changes or medication (e.g., allopurinol) may not always be effective in dissolving the stones.

How can the recurrence of urate uroliths be minimized?

Recurrence can be minimized by identifying and addressing the underlying cause, such as hepatic anomalies or genetic defects. Treatment includes promoting hydration, dietary management with reduced purine levels, and medication to manage uric acid levels. Regular monitoring through urinalysis and imaging is also essential.