 This is done to ensure that the majority of bowel can be reviewed.A KUB is a plain frontal supine radiograph of the abdomen.It is often supplemented by an upright PA view of the chest (to rule out air under the diaphragm or thoracic etiologies presenting as abdominal complaints) and a standing view of the abdomen (to differentiate obstruction from ileus by examining gastrointestinal air/water levels).