Gastroesophageal reflux in a child

This drawing shows where the esophagus and stomach are located in a child. The lower esophageal sphincter (LES) is a muscle that normally keeps stomach juices from backing up into the esophagus. The LES relaxes to allow food to enter the stomach and then closes to prevent the back-up of food and acid into the esophagus. Reflux can happen if the LES is weak or stays relaxed too long.