We wanted to investigate the incidence of posterior diaphragmatic defect on chest CT in various age gropus and its lateral chest radiographic appearances.

The chest CT scans of 78 patients of various ages with posterior diaphragmatic defect were selected among 1,991 patients, and they were analyzed for the incidence of defect in various age groups, the defect location and the herniated contents. Their lateral chest radiographs were analyzed for the shape of the posterior diaphragm and the posterior costophrenic sulcus.

The patients' ages ranged from 34 to 87 with the tendency of a higher incidence in the older patients. The defect most frequently involved the medial two thirds (n=49, 50.4%) and middle one third (n=36, 37%) of the posterior diaphragm. The retroperitoneal fat was herniated into the thorax through the defect in all patients, and sometimes with the kidney (n=8). Lateral chest radiography showed a normal diaphragmatic contour (n=51, 49.5%), blunting of the posterior costophrenic sulcus (n=41, 39.8%), focal humping of the posterior diaphragm (n=7, 6.8%), or upward convexity (n=4, 3.9%) of the posterior costophrenic sulcus on the affected side.

The posterior diaphragmatic defect discovered in asymptomatic patients who are without a history of peridiaphragmatic disease is most likely acquired, and this malady increases in incidence according to age. An abnormal contour of the posterior diaphragm or the costophrenic sulcus on a lateral chest radiograph may be a finding of posterior diaphragmatic defect.