Plain film identification of failure of interior vena caval-right atrial continuity.

The identification of absence of continuity of the inferior vena cava (IVC) with the right atrium assumes major importance at the time of right heart catheterization. The appearance of the IVC in the lateral chest radiogram is diagnostically different from the normal when discontinuity is present and 2 radiographic patterns have been recognized: 1) total absence of the IVC shadow; 2) straightened and posteriorly directed IVC shadow contrasting sharply with the anteriorly directed normally continuous IVC. This latter sign is considered reproducibly accurate in the identification of the IVC which fails to have continuity with the right atrium.