The word segment is derived from the Latin noun segmentum (“a piece cut off”) meaning part of a larger structure. Each segment has a pyramidal structure with its apex at the hilum and its base on the surface of the lung. It is supplied solely, with few collateral connections between segments, by the following structures: (1) a segmental bronchus as tertiary branch of the bronchial tree; (2) a segmental branch of the pulmonary artery (as well as the bronchial artery); and (3) a segmental (with or without an intersegmental) branch of the pulmonary vein together with lymphatics. Anatomic sublobar segmental resection, or segmentectomy, describes a technique of excision of lung tissue based on the bronchovascular anatomy.
Segments can be removed without affecting the functionality of the remaining lobe. A thorough knowledge of the human lung anatomy is mandatory for any surgeon before embarking on resection of individual segments. There are 10 segments in the right lung (3 in the upper lobe, 2 in the middle lobe, and 5 in the lower lobe) and 9 segments in the left lung (5 in the upper lobe and 4 in the lower lobe) (Fig. 71-1).
A schematic drawing of the different segments of the lungs. Note that the right lung has 10 anatomical segments, whereas the left lung has 9 segments only. Anterior view of the distal trachea, carina, right and left bronchial trees. Right upper lobe segments: 1: apical; 2: anterior; 3: posterior. Right middle lobe segments: 4: lateral; 5: medial. Right lower lobe segments: 6: superior; 7: medial basal; 8: anterior basal; 9: lateral basal; 10: posterior basal. Left upper lobe segments: 1 and 3: apical posterior; 2: anterior; 4: superior lingular; 5: inferior lingular. Left lower lobe segments: 6: superior; 7 and 8: anteromedial basal; 9: lateral basal; 10: posterior basal. Used with permission from Dr. Thomas W. Rice.
In 1939, Churchill and Belsey1 first described the technical aspects of a segmentectomy in a patient with bronchiectasis, based on prior work by others. This type of resection was originally limited to patients with infectious diseases such as bronchiectasis or tuberculosis, as lobectomy did not become the standard surgical resection for patients with lung cancer until the 1950s, as long as the size of the tumor and its location were amenable for this procedure. Otherwise pneumonectomy was still performed.
In 1973, Jensik and Faber et al.2 published a series of patients who underwent segmental resection for lung cancer that questioned the standard of lobectomy already at that time. Since then, limited resection for cancer has continued to be an area of controversy and has been plagued by conflicting studies comparing the technique with standard lobectomies and pneumonectomies. Other studies group segmentectomy and nonanatomic wedge resections together under the category sublobar resection and ...