Optimum radiographic evaluation for pneumoperitoneum
• Ideally, a frontal radiograph of the lower chest and upper abdomen with the patient in the upright position should be obtained to identify free air under the diaphragm.
• If there is an equivocal finding for pneumoperitoneum, then lateral decubitus views can be performed, as this is the most sensitive plain radiographic technique to detect intraabdominal free air.
• Supine frontal abdominal radiographs are insensitive for the detection of pneumoperitoneum, but these examinations are performed frequently so awareness of the diverse imaging manifestations of free air is important.
The radiologic diagnosis of pneumoperitoneum is one of the most important findings to make in all of radiology as it may be subtle and, if missed, could result in significant morbidity and mortality. Abdominal computed tomography (CT) is the most sensitive test to detect pneumoperitoneum and should be considered in cases in which clinical suspicion is high and plain radiographs are indeterminate or negative.