Accessory Left Lung Fissure with Rare Branching Pattern of Bronchial Tree

Abstract

Pulmonary fissures separate bronchopulmonary segments and delineate lungs into lobes Anatomical variation of these fissures lie on a continuum from completely fused lobes to accessory fissures in about 17.5% of right and 2% of left lungs. Hilar variations in the bronchial tree and vasculature can also be seen in lobar abnormalities.A routine dissection of an 83‐year‐old male cadaver showed an accessory fissure in the left lung. The hilum of the lung was further dissected for visualization of the bronchial tree and vasculature to explore mediastinal relationships and bronchopulmonary segments. Photographs were taken after dissection. The completeness of the accessory fissure and position of the pulmonary artery were classified using the Craig and Walker Scale.An accessory horizontal fissure forming a complete visceral cleft divided the superior and inferior lingular bronchopulmonary segments of the left lung. However, the fissure did not extend into the hilum at its base and may be classified as a Grade 2 fissure, a “complete visceral cleft but parenchymal fusion at the base.” While the pulmonary artery was positioned normally with reference to oblique fissure, the main and superior lobar bronchus showed variant branching pattern. The left main (primary) bronchus gave rise to the superior and inferior lobar (secondary) bronchi prior to entering the hilum. A normal division of the superior lobar bronchus was observed anterior to the pulmonary artery. The lingular branch of the superior lobar bronchus trifurcated into a rare accessory posterior segmental bronchus in addition to the normal superior and inferior segmental (tertiary) bronchi. The superior and inferior lingular bronchopulmonary segments separated by the accessory fissure were supplied by superior and inferior segmental bronchi, respectively, while the rare accessory posterior segmental bronchus supplied the base of the accessory fissure. The inferior lobar (secondary) bronchus showed normal division and was situated posterior to the pulmonary artery in the hilum. The mediastinal relationships showed the left pulmonary artery posterosuperior instead of anterosuperior to the main bronchus. No cardiac abnormalities were observed.Fewer structural abnormalities have been reported in the left lung in comparison to the right. Bilateral isomerism of the lungs is often associated with heterotaxia, wherein other structures in the chest and abdomen are also altered. In this case, while the left lung had two fissures similar to a right lung, there is no evidence of heterotaxia, suggesting that the abnormality arose from lung bud branching unilaterally during pulmonary development. Knowledge of possible accessory fissures and variant segmental bronchial branching is of clinical importance in understanding the pathological conditions, particularly for radiologists conducting imaging studies and pulmonologists and surgeons conducting bronchoscopies, biopsies and balloon bronchoplasties to place airway stents and lobectomies.Support or Funding InformationSupport from Touro College of Osteopathic Medicine.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.