Recognizing Primary Hyperoxaluria in Adults through Urine Oxalate Crystal Detection. Literature Review and Data Analysis.

In primary hyperoxaluria (PH), clinical manifestations can initiate during early childhood. Given the high prevalence of urinary lithiasis and chronic kidney disease (CKD) among adult population, in which clinical manifestations of PH after childhood, diagnosis becomes more difficult. This guide was developed to improve the diagnostic and therapeutic fields of PH in adult patients for clinicians. PH can cause (i) kidney stones and (ii) calcium oxalate crystal deposition within the kidney tissue (oxalate nephropathy). Clinical criteria for suspected PH in adults include the following: (i) Recurrent stone disease (in children, however, it should be suspected in the first episode); (ii) Nephrocalcinosis that is particularly associated with decreased glomerular filtration rate (GFR); (iii) Presence of oxalate crystals (calcium oxalate monohydrate and whewellite) in any biological fluid or tissue. To the above, the following can be added: (iv) Hyperoxaluria without clear cause of secondary hyperoxaluria; (v) Oxalate urinary excretion >1.0 mmol/1.73 m² body surface area in two samples; (vi) Kidney transplant recipients with previous CKD of unknown aetiology or previous history of recurrent urolithiasis and presenting graft nephrocalcinosis and GFR drop with no other clear cause. Routine PH screening of all adult patients with hyperoxaluria is costly strategy and therefore not recommended. Suspected PH in adults should be guided in accordance with clinical criteria. In patients with a confirmed PH diagnosis, all efforts should be directed towards adequate genetic and biochemical characterisation given that each patient can benefit from various therapeutic strategies.

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