A method and system for determining the residual volume within a patient having a naso-enteral feeding tube. A collection container is coupled to the naso-enteral feeding tube and a physical force is applied to the collection container to prevent stomach fluid from flowing into the collection container. The physical force is removed from the collection container and the stomach fluid is allowed to flow into the collection container. The volume of fluid within the collection container is determined, which represents the gastric residual volume of the patient. At least a portion of the collected volume of stomach fluid is returned to the patient from the collection container.