The Primary Hyperoxalurias: An Algorithm for Diagnosis

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Abstract
The primary hyperoxalurias (PHs) are inborn errors of metabolism resulting in increased urinary excretion of oxalate. Nephrolithiasis, nephrocalcinosis, and renal failure result. Renal failure can occur as early as infancy or as late as the sixth decade of life, and if not addressed promptly, results in severe morbidity and mortality related to systemic oxalate deposition (oxalosis). Clinicians are likely to encounter few PH patients during a practicing lifetime. Definitive diagnosis requires special studies performed in only a small number of laboratories worldwide. Accordingly, delays in diagnosis are common. An evidence-based guideline for diagnosis was developed. Patients with stones or nephrocalcinosis in childhood, recurrent calcium oxalate stones in adulthood, or renal insufficiency associated with stones or nephrocalcinosis should be evaluated for PH. A systematic approach to measurement of urine oxalate, glycolate and glycerate, and plasma oxalate is provided. Age-related variation in urine oxalate requires attention to normal ranges. Molecular analysis for mutations of the AGXT gene (PH, type I) or GRHPR gene (PH, type II) is definitive in some patients, while liver enzyme analysis is required for confirmation of the diagnosis in the remainder. An evidence-based algorithm will facilitate recognition and diagnosis of patients with the PHs, permitting earlier treatment.