Superior lobe of right lung

The superior lobe (upper lobe) of the right lung is the uppermost of the three lobes of the right lung, separated from the middle lobe by the horizontal (minor) fissure and from the lower lobe by the oblique (major) fissure.

Key anatomical features:

• Lobar boundaries: The superior lobe sits above the horizontal fissure anteriorly and above the upper portion of the oblique fissure posteriorly. The horizontal fissure most commonly meets the anterior chest wall at the level of the fourth rib and originates from the middle third of the oblique fissure. The right oblique fissure is typically located posteriorly at the fifth rib and laterally at the sixth rib.

• Bronchial anatomy: The right upper lobe bronchus (RULB) arises from the right main stem bronchus and typically divides into three segmental bronchi B1 (apical), B2 (posterior), and B3 (anterior) supplying the three bronchopulmonary segments of the lobe. This classic trifurcation pattern is the most common (~59-64%), though bifurcated and other variant patterns occur in approximately 35% of cases.

• Vascular supply: The pulmonary arterial supply to the right upper lobe typically arises from a superior trunk (truncus anterior) of the right pulmonary artery. The bronchovascular relationships are distinctive: the subsegmental arteries tend to lie along the medial aspect of their corresponding bronchi, which is opposite to the pattern seen in the middle lobe.

• Segmental volumetry: Among the three segments, the anterior segment (S3) is volumetrically predominant in approximately 52% of cases, while equal distribution across all three segments is uncommon (~5%).

• Fissural variability: The horizontal fissure separating the upper and middle lobes is frequently incomplete (67%) or absent (11%), which has important implications for collateral ventilation, disease spread between lobes, and surgical planning.