1. Albert Ross, MD* 2. Neal S. LeLeiko, MD, PhD* 1. *Division of Pediatric Gastroenterology, Nutrition and Liver Diseases, Hasbro Children's Hospital/Rhode Island Hospital, Providence RI. After completing this article, readers should be able to: 1. Understand the principal causes of acute abdominal pain in children. 2. Describe the characteristics of visceral versus somatic abdominal pain. 3. Be familiar with the differential diagnosis of abdominal pain based on symptoms and location of pain. 4. Discuss the evaluation of acute abdominal pain. 5. Distinguish surgical from medical abdominal pain. “ Hello, Doctor Jones, Billy has an awful tummy ache!” For such a simple statement, so many possible outcomes exist. Is this an emergency? Does he have appendicitis? Does he need a surgeon? Is this something trivial? Has Billy eaten something harmful? Is he constipated? Acute abdominal pain can be caused by myriad conditions whose outcomes vary from rapid improvement to surgery, posing a diagnostic Gordian Knot. However, through evaluation of the patient's history and symptoms and the use of technology, a pediatrician usually can arrive at a reasonable conclusion about the care of the patient, even if the diagnosis still is undetermined. Acute abdominal pain can be classified according to its location and nature, history, or associated signs (Table 1). View this table: Table 1. Differential Diagnosis Mapped to Location of Abdominal Pain Some conditions can cause pain in different regions, and it may be difficult to associate the disease with the location of the pain. Localization of the source of abdominal pain is confounded by the nature of the pain receptors involved. Further, the type of pain associated with a particular disease may change as the disease process progresses, as in appendicitis. Abdominal pain may be classified as visceral, somatoparietal, and referred pain. Most abdominal pain is associated with visceral pain receptors. Visceral pain receptors …