By far, the commonest indication for abdominal plain film radiography is abdominal pain. In examining an abdominal plain film, it is often helpful to have a systematic approach because many findings are subtle and easily overlooked. An upright chest or abdominal radiograph should include the diaphragms, which should be checked for abnormal subphrenic radiolucencies. Splenic enlargement due to trauma or medical disease may be suggested by displacement of the splenic flexure, gastric bubble, or left kidney. Linear radiolucencies in the liver indicate gas in the biliary or portal systems. This finding associated with small bowel obstruction suggests gallstone ileus. A variety of abnormal radio densities can be encountered on plain films. Most are due to abnormal calcifications within the soft tissues, although they can also be caused by foreign bodies, surgical clips, pills, or intramuscular injections. Plain films are rarely indicated in the evaluation of gastrointestinal hemorrhage or gastroenteritis.