Risk factors for urolithiasis in children on the ketogenic diet

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.

Ketogenic diet guidelines for infants with refractory epilepsy

“…In addition to the age factor, the presence of hypercalciuria also increases the risk for the development of kidney stones [44]. Uric acid, calcium oxalate, calcium phosphate or mixed composition stones have been reported in up to 7% of children on the KD [44][45][46].…”

“…Uric acid, calcium oxalate, calcium phosphate or mixed composition stones have been reported in up to 7% of children on the KD [44][45][46]. Risk may be higher with long-term treatment [29] and concurrent use of carbonic anhydrase inhibitors [47].…”

Improving tolerability of the ketogenic diet in patients with abnormal endoscopic findings

“…Even though efficacy and safety have been demonstrated in several studies over the past decade [1][2][3][4], GI intolerability and various other complications have limited its use in many patients [5][6][7][8][9]. A high-fat diet prolongs gastric emptying time and can cause vomiting, especially in patients with gastroesophageal reflux [12].…”

“…Despite its potent antiepileptic efficacy, wide application of the KD for long-term maintenance has been limited in some children by poor tolerability [5][6][7][8]. Significant numbers of patients suffer from GI discomfort during KD treatment, in addition to its unpalatability [9].…”

Risk Factors for Urolithiasis in Gastrostomy Tube Fed Children: A Case-Control Study

“…Previous epidemiologic studies have suggested that low water intake, 1 high protein diets, 2,3 and ketogenic diets [4][5][6] are all associated with increased risk of urolithiasis in the general population. Although these and other factors may be important risk factors in G-tube fed (GTF) children, previous studies have not specifically examined possible associations.…”