Right upper lobe versus right middle lobe: differentiation with thin-section, high-resolution CT.

A new method was developed to differentiate the upper lobe from the middle lobe of the right lung with thin-section, high-resolution computed tomography. In the upper lobe, a medial subsegmental bronchus of an anterior segmental bronchus is always located lateral to the corresponding artery. In the middle lobe, a medial subsegmental bronchus of a lateral segmental bronchus and a superior and inferior subsegmental bronchus of a medial segmental bronchus are always located medial to the corresponding artery. In other words, the anatomic relationship between the subsegmental bronchi and the corresponding pulmonary arteries in the upper lobe is opposite to that in the middle lobe. One hundred seventeen cases, including 54 cases of lobar volume loss, were reviewed with this method, and in each case it was possible to differentiate the upper lobe from the middle lobe without the contiguous section analysis.