General diagnostic approach and preoperative management include the following: Giving nothing by mouth Placing a nasogastric tube to prevent further bowel distention or possible aspiration of vomitus Correcting fluid and electrolyte disturbances Taking a plain abdominal x-ray Doing a contrast enema to delineate the anatomy (the enema may also relieve obstruction in meconium plug syndrome or meconium ileus) For Hirschsprung disease, a rectal biopsy is needed.