Kidney Stones

Hyperuricosuria is a Risk Factor for Calcium Oxalate Stones

February 2010

Increased urinary uric acid excretion has also been identified as a risk factor for calcium oxalate stones. The mechanism is not entirely clear, and at least 3 hypotheses have been put forth. Increased urinary uric acid may serve to salt out calcium oxalate, which is already almost always supersaturated in the urine. Uric acid crystals could also serve as heterogeneous nucleation sites for calcium oxalate. Finally, uric acid and/or uric acid crystals could bind and inactivate urinary macromolecular inhibitors. Varying degrees of evidence exist for each of these possibilities. Treatment for this subgroup of patients includes allopurinol, which blocks uric acid production, as well as potassium citrate, which presumably acts to block uric acid precipitation in the urine.

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Jump to section:

• Introduction
• Kidney Stones
• Why do Kidney Stones Form?
• Genetics and Environment
• Not All Stones are Created Equal: Stone Analysis is Very Helpful
• Laboratory Evaluation
• Supersaturation Index
• Components of the Urinary Supersaturation Profile
• Uses of Urinary Supersaturation
• Common Features Increase Urinary Supersaturation in Patients with Idiopathic Calcium Oxalate Nephrolithiasis
• "Conservative" Dietary Recommendations for Calcium Oxalate Stone Formers
• Causes of Hypercalciuria
• Genetic Hypercalciuria
• Genetic Hypercalciuria: Treatment
• What is Oxalate?
• Hyperoxaluria: What is the Relevant Concentration?
• Oxalate Balance on a Typical Western Diet
• Enteric Hyperoxaluria is Caused by Fat Malabsorption
• Control of Urinary Citrate: Largely Due to Systemic Acid Base Balance
• Treatments for Enteric Hyperoxaluria
• Low Urinary Citrate
• Hyperuricosuria is a Risk Factor for Calcium Oxalate Stones
• Uric Acid is Very Insoluble at Low pH
• Calcium Phosphate is Very Insoluble at High pH!
• Cystine Stones
• Struvite stones
• Questions?