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Risk factors for urolithiasis in children on the ketogenic diet
S L Furth1, J C Casey, P L Pyzik
1Division of Pediatric Nephrology, Johns Hopkins University School of Medicine, Baltimore, MD 21287-2535, USA. sfurth@jhmi.edu
Insights
The ketogenic diet, used for epilepsy, increases kidney stone risk in children. Younger age and high urine calcium are key risk factors, alongside low citrate and acidic urine.
Area of Science:
- Pediatric Nephrology
- Metabolic Disorders
- Neurology
Background:
- The ketogenic diet is an established therapy for drug-resistant epilepsy in children.
- Kidney stone formation (urolithiasis) has been anecdotally linked to ketogenic diet use.
- Identifying risk factors is crucial for managing potential complications.
Purpose of the Study:
- To investigate risk factors associated with kidney stone development in children on the ketogenic diet.
- To determine the incidence of urolithiasis in a cohort of children initiating the ketogenic diet.
Main Methods:
- A case-control study compared children with ketogenic diet-associated stones to non-stone-forming controls.
- Prospective follow-up of 112 children initiating the ketogenic diet evaluated stone incidence.
- Urine parameters including calcium, creatinine, pH, and citrate were analyzed.
Main Results:
- Younger age at initiation and hypercalciuria were identified as risk factors for stones.
- The incidence of stone formation was 0.8 children per 100 patient-months at risk.
- Elevated fasting urine calcium:creatinine ratios increased from 40% at baseline to 75% at 6 months.
- Urinary citrate excretion significantly decreased on the ketogenic diet.
- Patients often exhibited hypercalciuria, acidic urine, and low urinary citrate.
Conclusions:
- Children on the ketogenic diet are at high risk for uric acid and calcium stones.
- Risk factors include younger age, hypercalciuria, acidic urine, and low urinary citrate.
- Monitoring and potential interventions are necessary to mitigate stone risk.
Abstract:
Kidney stones have been associated with use of the ketogenic diet in children with refractory seizure disorders. We performed a case-control study examining risk factors for the development of stones on the ketogenic diet, and prospectively followed children initiating the ketogenic diet to evaluate the incidence of urolithiasis. Clinical characteristics of 18 children presenting with stones (8 uric acid stones, 6 mixed calcium/uric acid stones, 1 calcium oxalate/phosphate stone, 3 stones not evaluated) were compared with characteristics of non-stone-forming children initiating the ketogenic diet at Johns Hopkins since July 1996. Since July 1996, 112 children initiating the ketogenic diet have been followed for development of stones. Follow-up times on the diet range from 2 months to 2.5 years. Of 112 children, 6 have developed stones (3 uric acid, 3 mixed calcium/uric acid stones) (0.8 children developing stones/ 100 patient-months at risk). Comparisons of children presenting with stones on the ketogenic diet with characteristics of the entire cohort initiating the ketogenic diet suggest younger age at diet initiation and hypercalciuria are risk factors for the development of stones. Prospective evaluation of children initiating the ketogenic diet revealed that almost 40% of patients had elevated fasting urine calcium: creatinine ratios at baseline; this increased to 75% after 6 months on the diet. Median urine pH was 5.5 at diet initiation, and remained at 6.0 thereafter. In a subset of patients tested, urinary citrate excretion fell from a mean of 252 mg/24 h pre diet initiation to 52 mg/24 h while on the diet. Uric acid excretion remained normal. Patients maintained on the ketogenic diet often have evidence of hypercalciuria, acid urine, and low urinary citrate excretion. In conjunction with low fluid intake, these patients are at high risk for both uric acid and calcium stone formation.