Pain in the belly (abdomen) can come from conditions affecting a variety of organs. The abdomen is an anatomical area that is bounded by the lower margin of the ribs above, the pelvic bone (pubic ramus) below, and the flanks on each side. Although abdominal pain can arise from the tissues of the abdominal wall that surround the abdominal cavity (for example, skin and abdominal wall muscles), the term abdominal pain generally is used to describe pain originating from organs within the abdominal cavity (for example, beneath the skin and muscles). These organs include the stomach, small intestine, colon, liver, gallbladder, and pancreas. Occasionally, pain may be felt in the abdomen even though it is arising from organs that are close to but not within the abdominal cavity, for example, the lower lungs, the kidneys, and the uterus or ovaries. This latter type of pain is called "referred" pain because the pain, though originating outside the abdomen, is being referred to (felt) in the abdominal area. Abdominal pain can be acute and sudden in onset, or the pain can be chronic and longstanding. Abdominal pain may be minor and of no great significance, or it can reflect a major problem involving one of the organs in the abdomen. The characteristics of the pain -- location, timing, duration, etc. are important in diagnosing its cause. Persisting abdominal pain should be evaluated by a physician. Various causes of abdominal pain include, but are not limited to, indigestion after eating, gallstones and gallbladder inflammation (cholecystitis), pregnancy, gas, inflammatory bowel disease (ulcerative colitis and Crohn's disease), appendicitis, ulcers, gastritis, gastroesophageal reflux disease (GERD), pancreatitis, gastroenteritis (viral or bacterial), parasite infection, endometriosis, kidney stones (nephrolithiasis), abdominal muscle injury, abdominal hernia, lactose intolerance, gluten intolerance (celiac disease), food poisoning, menstrual cramps, peritonitis, serositis, ischemic bowel disease, vasculitis, abdominal aneurysm, abdominal organ injury from trauma, and constipation.