Hyperuricosuria

TL;DR. Erbliche Stoffwechselstörung mit überschüssiger Harnsäure im Urin und erhöhtem Risiko für Blasen- oder Nierensteine.

Dalmatians are highly predisposed to hyperuricosuria due to a historical genetic link.

Was ist das?

Hyperuricosuria (HUU) is an inherited defect of uric acid handling (SLC2A9). Uric acid is poorly converted to soluble allantoin and poorly reabsorbed in the kidney, so high urinary uric acid forms ammonium biurate crystals and urate stones that can obstruct the urinary tract.

Ursachen und Risikofaktoren

Autosomal recessive SLC2A9 mutation: two copies required for the metabolic phenotype. Stone risk rises with concentrated acidic urine, diet, and male anatomy (long narrow urethra / os penis). Predisposed breeds include Dalmatian, English Bulldog, Black Russian Terrier, Weimaraner, and others.

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• Ammonium biurate crystalluria ("thorny apple" crystals on sediment)
• Urate urolithiasis: hematuria, dysuria/stranguria, pollakiuria, indoor accidents
• Urinary obstruction (emergency): unproductive straining, genital licking, abdominal pain, vomiting, collapse

Straining to urinate is a key clinical sign of urinary stones in predisposed breeds.

Diagnose

DNA test for SLC2A9 (clear / carrier / affected). Fresh urinalysis for biurate crystals and pH. Abdominal ultrasound preferred because pure urate stones are often radiolucent on plain radiographs. Optional 24-hour urinary uric acid quantification.

Ultrasound is the preferred imaging method to detect radiolucent urate stones.

Behandlung

Lifelong low-purine, high-moisture diet; promote water intake. Target alkaline urine (often pH >7). Potassium citrate if diet alone fails. Allopurinol only with strict low-purine feeding (risk of xanthine stones). Surgery, lithotripsy, or urohydropropulsion for obstruction or non-dissolvable stones.

Prognose

Good with lifelong diet and monitoring. Stones commonly recur if purine intake rises or hydration falls.

Vorbeugung

DNA screening of breeding stock; avoid carrier x carrier / affected pairings. Early low-purine diet and hydration in affected dogs can prevent clinical stones.

Wann den Tierarzt rufen

Emergency: straining with no urine, severe pain, vomiting, marked lethargy. Complete blockage can cause kidney failure, bladder rupture, and death within 24-48 hours.

Bei bestimmten Rassen

Nearly all purebred Dalmatians historically excreted high uric acid; LUA (low uric acid) lines reintroduce normal SLC2A9. English Bulldogs and Black Russian Terriers also high risk, especially males for obstruction.

Quellen

• Small Animal Internal Medicine, 5th Edition, pages 728-729.
• Cowell and Tyler's Diagnostic Cytology and Hematology of the Dog and Cat, 5th Edition, page 416.

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