Crystalluria: A clinically useful investigation in children with primary hyperoxaluria post-transplantation

Primary hyperoxaluria type I (PH 1) is a congenital error of metabolism that can be manifested by an increased oxalate production, and ultimately result in kidney failure. After a combined liver/kidney transplantation, children with PHI have persistant excretion of oxalate that causes crystal formation in the urinary tract, and could result in systemic oxalosis and eventual graft failure. We speculated that crystalluria may be predictive of this nephrolithogenic tendency and thus investigated the effect of an intensive therapeutic strategy to prevent crystal formation in 13 children at our hospital. Oxalate crystal volume (OCV) measurements were performed at regular intervals for 36 months, and compared with urine supersaturation measurements. We found that crystalluria with the OCV measurement is non- invasive, easily performed, and gives feedback on the efficacy of PH I therapy within one hour. Further study is needed to determine whether this method is a better predictor of nephrocalcinosis than is supersaturation alone.