Bronchus Intermedius: Anatomy, Location, CT & Lateral Chest X-Ray, Cancer, Stenosis, Malacia & Arterial Supply

Content:

• What is Bronchus Intermedius?
• Anatomy
• Location
• CT & Lateral Chest X-Ray
• Cancer
• Stenosis
• Malacia
• Arterial Supply

What is Bronchus Intermedius?

The bronchus intermedius is a part of the right main bronchus in the respiratory system. It serves as the airway connecting the right main bronchus to the right middle and lower lobes of the lung. Functionally, it acts as a critical passage for airflow, enabling proper ventilation of these lobes. Any obstruction, narrowing, or disease affecting this bronchus can significantly impact lung function and respiratory health.

Clinically, the bronchus intermedius is important because it is a common site for pathologies such as stenosis, malacia, or neoplasms. Its anatomical location and relationship to adjacent vascular structures make it significant for pulmonologists, thoracic surgeons, and radiologists. Understanding its anatomy is essential for procedures like bronchoscopy, stent placement, or surgical interventions in cases of tumors or airway compromise.

Anatomy

The bronchus intermedius originates from the right main bronchus after the take-off of the right upper lobe bronchus. It is a relatively short segment that travels downward and backward before bifurcating into the right middle lobe and right lower lobe bronchi. Its walls are composed of cartilage, smooth muscle, and mucosal lining, similar to other bronchi, allowing structural support and flexibility.

Anatomically, it lies adjacent to major structures such as the pulmonary artery, right atrium, and esophagus, which is critical during imaging or surgical procedures. Lymph nodes surrounding the bronchus intermedius, such as subcarinal nodes, are often evaluated in cases of malignancy. Knowledge of its branching and relationships ensures safe navigation during endoscopic procedures and accurate interpretation of radiological findings.

Location

The bronchus intermedius is located in the right lung, specifically between the take-off of the right upper lobe bronchus and the bifurcation into the middle and lower lobe bronchi. It lies posteriorly to the pulmonary artery and anterior to the esophagus. The bronchus runs approximately 2–2.5 cm in length, but this can vary slightly depending on patient anatomy.

Its location is clinically relevant because it is prone to obstruction by tumors, strictures, or foreign bodies. Due to its central position, compromise of the bronchus intermedius may affect ventilation of both the right middle and lower lobes simultaneously, leading to segmental or lobar atelectasis and reduced respiratory efficiency.

CT & Lateral Chest X-Ray

On CT imaging, the bronchus intermedius can be visualized as a tubular airway connecting the right main bronchus to its distal branches. CT provides excellent detail of the bronchial walls, lumen, and surrounding structures, which is helpful for identifying lesions, narrowing, or inflammation. Contrast-enhanced scans can further highlight adjacent vasculature and lymph nodes.

On a lateral chest X-ray, the bronchus intermedius is indirectly visualized as part of the bronchial tree. Collapse of the right middle or lower lobe or a mass compressing the bronchus intermedius can be inferred by lobar opacities or air-trapping patterns. Radiologists often combine lateral and frontal views with CT for accurate localization and assessment of pathology.

Cancer

The bronchus intermedius is a potential site for primary bronchogenic carcinoma or metastatic lesions. Tumors in this location may cause partial or complete obstruction of airflow to the right middle and lower lobes, leading to symptoms like persistent cough, hemoptysis, dyspnea, or recurrent pneumonia.

Diagnosis typically involves imaging studies such as CT or PET-CT, bronchoscopy with biopsy, and sometimes endobronchial ultrasound (EBUS) to evaluate lymph node involvement. Early detection is crucial, as bronchus intermedius tumors can rapidly compromise ventilation and spread to mediastinal lymph nodes.

Stenosis

Stenosis of the bronchus intermedius refers to abnormal narrowing of its lumen. Causes may include post-intubation injury, previous surgical interventions, inflammation, or tumors. Stenosis reduces airflow to the right middle and lower lobes, resulting in respiratory symptoms such as wheezing, cough, recurrent infections, or lobar collapse.

Treatment of bronchus intermedius stenosis may involve bronchoscopic dilation, stent placement, or surgical resection depending on the severity and underlying cause. Accurate imaging and bronchoscopy are essential to guide therapy and monitor for recurrence.

Malacia

Bronchomalacia is a condition characterized by weakness and collapse of the bronchial walls during exhalation. In the bronchus intermedius, malacia can cause dynamic airway obstruction, leading to airflow limitation, chronic cough, and recurrent lower respiratory infections.

Diagnosis is typically made via bronchoscopy, which can visualize dynamic collapse, and confirmed by expiratory CT imaging. Management may include positive airway pressure therapy, stent placement, or surgical reconstruction in severe cases. Malacia is an important differential diagnosis when patients present with unexplained respiratory symptoms despite normal lung parenchyma.

Arterial Supply

The arterial supply of the bronchus intermedius comes primarily from the bronchial arteries, which branch off the thoracic aorta. These arteries provide oxygenated blood to the bronchial walls and surrounding tissues. The venous drainage occurs via bronchial veins into the azygos system.

Understanding the arterial supply is critical during surgical procedures, biopsies, or stent placement, as inadvertent injury can cause significant bleeding. Additionally, the proximity of the bronchial arteries to mediastinal structures emphasizes the need for careful imaging and anatomical knowledge during interventions.