CT appearance of diaphragmatic pseudotumors

Invaginations of the muscular fibers of the diaphragm into the upper abdomen may appear as nodules of soft tissue density on computed tomographic (CT) sections in deep inspiration. If these nodules indent the adjacent stomach or distal transverse colon, they may mimic small mural tumors or metastatic implants. Similar nodules protruding from the diaphragmatic crura into the adjacent retroperitoneal fat may be mistaken for enlarged lymph nodes on CT. Differential diagnosis of these pseudotumors from pathologic lesions is based on their continuity peripherally with the diaphragm and their separation from the hollow viscera by subdiaphragmatic fat. Decubitus and expiratory CT sections are valuable diagnostic aids.