 1. Patients with a history of a metabolic disorder including documented defect in urea metabolism including documented history of gout, carnitine deficiency primary carnitine deficiency, carnitine palmitoyltransferase I or II deficiency, carnitine translocase deficiency, fatty acid metabolism, beta-oxidation defects, pyruvate carboxylase deficiency, mitochondrial function, porphyria, or nephrolithiasis. 