Functional Gastroenterology: Assessing & Addressing the Causes of Functional Gastrointestinal Disorders (2nd edition) is a textbook written by Dr. Steven Sandberg-Lewis for clinicians wishing to expand their understanding of the Naturopathic approach to the comprehensive care of gastrointestinal complaints. After teaching pathology for 17 years, Dr. SS-L shifted gears to explain his approach to optimizing the health of the GI tract.