Tracheal bronchus

5 month old male child with acute respiratory tract infection, CT coronal reformatted lung window shows bronchus arising from the trachea on right side (arrow) and the virtual bronchoscopy image shows the tracheal bronchus opening better.

The term tracheal bronchus refers to an abnormal bronchus that comes directly off the lateral wall of the trachea (ie, above the main carina) and supplies ventilation to the upper lobe. It is most often an asymptomatic anatomical variant found on bronchoscopy. There is an association

between tracheal bronchus and other congenital malformations, mainly malformations of the ribs and vertebrae. Patients with Down syndrome have a higher incidence of tracheal bronchus. The anomalous bronchus can arise anywhere from the carina to the cricoid cartilage, but most frequently within 2 cm of the carina. Tracheal bronchi are classified as being either “displaced” or “supernumerary.”

If the entire right upper lobe takes off from the trachea the right main bronchus is the bronchus intermedius, feeding the right middle and lower lobes, and the malformation is called “true tracheal bronchus” or “bronchus sui” (“pig bronchus,” because that is the normal morphology in pigs). The incidence of true tracheal bronchus is 0.2%.

If the anomalous bronchus is the take-off of the apical segment of the right upper lobe, as was the case in our patient, the right main bronchus will be normal looking, but the right upper lobe will not have its trifurcation. Instead there will be a bifurcation, corresponding to the anterior and posterior segments. That variant is called “apical tracheal bronchus,” which has been described in patients who have an azygos lobe. In that situation the apical segment will have its own displaced bronchus and its ownpleural investment. Vascular supply and venous drainage are usually normal in the displaced bronchus variant and are provided by the pulmonary artery and pulmonary veins.

The majority of patients with tracheal bronchi are asymptomatic and do not require any medical intervention. In the case of recurrent pneumonia complicated by bronchiectasis surgical resection of the anomalous lobe or segment is the treatment of choice.

Small-cell lung carcinoma invading the left atrium

60 year old male came with progressive shortness of breath and chest pan, Contrast enhanced CT scan showed large heterogenously enhancing lesion (arrow in first image) in the left perihilar and lower lobe region occluding the left lower lobe bronchus completely. The lesion is partially encasing the descending thoracic aorta and extending in to the left atrium through the inferior pulmonary veins (arrow in secong image and arrow head in third image) . The biopsy of the lesion revealed Small cell carcinoma of lung.

Direct intravascular, cardiac extension and spread of bronchogenic carcinoma is an uncommon event. when tumor extends to left atrium, special techniques are needed is resectrion of still to be attempted.

The cardinal imaging signs of intarvenous extension of bronchogenic carcinoma on CT or MRI is filling defect of soft tissue density within the lumen of pulmonary vein and left atrium, which is continous with the primary mass. Obliteration of superior pulmonary vein is regardes as suggesting as intrapericardial tumor extension. CT remains the standard staging investigation for lung carcinoma.

Congenital Cystic Adenomatoid Malformation (CCAM)

2 Month old male baby came with shortness of breath. CT scanogram shows large cystic lesion in the right upper zone. Axial and coronal CT lung window shows large cyst in the right upper lobe with septa within s/o Typer I congenital cystic adenomatoid malformation.

CCAM is a congenital anomaly of the terminal brochioles which results in a dysplastic, multicystic mass. These cysts usually communicate with the bronchial tree. At birth, these cysts are fluid-filled. Ultimately, communication with the airway allows for the fluid-filled mass to become air-filled. Whether fluid-filled or air-filled, the cysts become increasing larger, exert mass effect, compress mediastinal structures and lung parenchyma.

Infants less than one year old usually present with respiratory distress. Usually, the abnormality is confined to one lobe. There are three types of CCAM:

1. Type I: Single/multiple cysts > 2cm (most common).
2. Type II: Smaller cysts <2cm
3. Type III: Solitary solid mass. (Multiple microcysts of 2-6 mm).

The differential diagnosis includes congenital lobar emphysema and bronchial atresia.

Treatment: Surgical lobectomy is curative with Type I. There is increased morbidity and mortality with Type II and II because the lesions are often larger at presentation.

References:

1. Brickman H. Pediatric Radiology: The Requisites, 2nd Edition, 1998.
2. Swischuk L. Imaging of the Newborn, Infant and Young Child, 3rd Edition, 1989.