Accessory fissures of the lung: evaluation by high-resolution computed tomography.

This study was performed to classify and assess the frequency of accessory fissures of the lung by high-resolution CT (HRCT) scans. The HRCT scans of 443 patients were retrospectively reviewed. After exclusion of patients with pulmonary parenchymal distortion, pleural disease or those who had had lobectomy, 186 patients were included in the study. The HRCT scans consisted of 1.5-mm sections obtained at 10-mm intervals and reconstructed with a high-spatial-resolution algorithm. In 59 of 186 patients (32%), a total of 69 accessory fissures were detected. The most common fissure was the inferior accessory fissure ( n=40; 21%, 38 on the right, 2 on the left) followed by the left minor fissure ( n=17; 9%). Other accessory fissures observed were the right superior accessory fissure ( n=2; 1%), the azygos fissure ( n=1; 0.5%) and intersegmental fissures between the medial and lateral segments of the right middle lobe ( n=3; 2%), the superior and inferior segments of the lingula ( n=2; 1%), the anterobasal and laterobasal segments of both the right ( n=1; 0.5%) and the left ( n=3; 2%) lower lobe. In conclusion, the inferior accessory fissure and the left minor fissure were the most common accessory fissures seen on HRCT examinations.