OBJECTIVE: Kidney stones are an adverse event with the ketogenic diet (KD), occurring in ∼6% of children who are started on this therapy for intractable epilepsy. Potassium citrate (Polycitra K) is a daily oral supplement that alkalinizes the urine and solubilizes urine calcium, theoretically reducing the risk for kidney stones.
METHODS: Children who started the KD from 2000 to 2008 at Johns Hopkins Hospital, with at least 1 month of follow-up, were evaluated (N = 313). From 2000 to 2005, children were treated with daily Polycitra K at 2 mEq/kg per day only in the setting of identified hypercalciuria, whereas, since 2006, it has been started for all children empirically at KD onset.
RESULTS: Polycitra K was administered to 198 children preventatively overall, 4 (2.0%) of whom developed kidney stones, compared with 11 (10.5%) of 105 who did not receive Polycitra K (P = .003). Two children since 2006 refused Polycitra K, 1 of whom developed a kidney stone. Successful empiric administration of Polycitra K at KD onset resulted in a kidney-stone incidence of 0.9% (1 of 106) compared with administration only because of hypercalciuria, 6.7% (13 of 195; P = .02). Polycitra K resulted in less acidic urine (mean pH: 6.8 vs 6.2; P = .002) but not reduced serum acidosis. No adverse effects of oral citrates were reported.
CONCLUSIONS: Oral potassium citrate is an effective preventive supplement against kidney stones in children who receive the KD, achieving its goal of urine alkalinization. Universal supplementation is warranted.