A scanning electron microscopic study on the pathogenesis of the posterolateral diaphragmatic hernia.

A scanning electron microscopic and light microscopic examination of a left posterolateral diaphragmatic hernia in a 14.7 day rat fetus gives new insight for the pathogenesis of this anomaly. Compared to control specimens of the same age, the pleuroperitoneal canal is larger and round rather than crescent-shaped. Evidence is presented which indicates that the caudal pole of the left lung protruded into the canal region during the 14th day, it appears that the lung interferes with the apposition and fusion of the dorsal and ventral pleuroperitoneal folds. The presence of the lung within the pleuroperitoneal canal prevents canal closure and results in the formation of a posterolateral diaphragmatic hernia.