inferior accessory fissure

in·fe·ri·or ac·ces·so·ry fis·sure

the fissure that commonly separates the medial basal segment of the right lower lobe of the lung from the other basal segments, occasionally seen as an oblique line near the right heart border on chest radiographs.
References in periodicals archive ?
The inferior accessory fissure which demarcates the medial basal segment and the superior fissure which demarcates the superior segment, are the most common accessory fissures detected on CT scans (David & Tarver).