Posterior pulmonary lobe: segmental and vascular anatomy in human specimens.

The posterior pulmonary lobe (PPL) is defined by an aberrant fissure running horizontally on the costal surface of the lower lobe. We studied the frequency of the PPL, and the ramification of bronchi and vessels in the PPL, and so describe mainly these differences compared to the normal lung. Nineteen PPL cases (15 right and 4 left) were found in 273 (116 right and 157 left) human lung specimens. The incidence of PPL was 13% on the right side and 3% on the left side. The PPL frequently (right 87%, left 50%) corresponded to S(6) (superior segment). Analysis of the ramification of bronchi revealed that B(7) (medial basal bronchus) tended to form a common trunk with B* (subsuperior bronchus) or B(8) (anterior basal bronchus). Analysis of the ramification of veins revealed that V(6) (superior vein) tributaries were often double, and V(6) tended to disperse widely. Anomalies in which the segmental artery and vein communicated with other segments were found in seven cases (37%) (4 arteries and 3 veins, 6 right and 1 left) in PPL. These results show that the PPL does not always correspond to S(6) and frequently has an anomalous vessel from other segments. This is valuable surgical information, particularly in S(6) segmentectomy.