Unilateral dilatation of the internal mammary artery as a sign of an intrathoracic lesion.

Nineteen children had unilateral dilatation of the internal mammary artery associated with an intrathoracic lesion on the same side. Dilatation of one internal mammary artery to a calibre more than twice that of the artery on the other side is a sign of an intrathoracic pathological finding on the same side. However, when the arteries have the same calibre an intrathoracic pathological process is not excluded. Dilatation occurs independently of the vascular supply of the pathological process by systemic collaterals. A share in the collateral supply from the pulmonary circulation is specially characteristic.