It is known that many urea-splitting bacteria also exist in the gut, and that in healthy individuals, approximately 15-30% of blood urea is degraded via gut bacteria into ammonia3, which returns to the liver via the portal vein, only to be recycled into urea. This percentage of degraded urea may even be greater in patients with urea cycle disorders, who are on a low protein-diet4 and whose gastrointestinal contents thus likely have lower nitrogen content, promoting bacterial recycling of nitrogen from available urea. Additionally, urea hydrolysis has been shown to be greatest in infants5, precisely the age at which hyperammonemic episodes are the most frequent in UCD patients.