Because there are many causes of acute abdominal pain, a systematic approach by the evaluating physician is necessary to narrow the differential diagnosis. It is vital that the physician have an understanding of the mechanisms of pain generation and be familiar with the presentations of common diseases that cause abdominal pain. Recognizing the red flags in the history and physical examination and the initial imaging and laboratory findings helps to determine which patients may have a serious underlying disease process, and therefore warrant more expedited evaluation and treatment.