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Cardiac bronchus

Dr Yuranga Weerakkody and Dr Frank Gaillard et al.

A cardiac bronchus is a rare variant of normal bronchial anatomy, arising from the medial aspect of the bronchus intermedius.

Epidemiology

This anomaly is rare and is reported in around 0.09 to 0.5% of individuals ^3-5. There may be a predilection for males. It is the only recognised true supernumerary bronchus, with other anomalies representing aplasia or abnormal branching patterns ³.

Clinical presentation

The vast majority of cardiac bronchi are asymptomatic. In some patients with lung parenchyma supplied by this bronchus, abnormal drainage predisposes to repeated chest infection ². Haemoptysis has also been described ⁴.

Pathology

The anomaly is thought to occur between the 4^th and 6^th weeks of gestation, during development of the bronchial tree ³.

The histology of its wall is that of normal airway.

A cardiac bronchus arises from the bronchus intermedius, opposite and just distal to the origin of the right upper lobe bronchus. It is variable is size, morphology and length (range from 5mm to 5cm)^1,3. In about half of cases the cardiac bronchus is a short blind ending bronchial stump with no branches and does not supply any lung parenchyma. In the remainder, the bronchus may have branches and a an amount of aerated lung parenchyma ¹.

Radiographic features

A cardiac bronchus is almost always an incidental finding of CT examination of the chest. It appears as a continuation of the the lumen of the right main bronchus, projecting medially and directly inferiorly towards the posterior aspect of the heart.

In some cases the dependent lung parenchyma may be collapsed and mimic a soft tissue mass ².

Treatment and prognosis

As these structures are usually asymptomatic no treatment is required. In rare instances where recurrent infections can be attributed to a cardiac bronchus then surgical resection may be carried out ³.

Differential diagnosis

There is usually little if any differential diagnosis as most cases are classical in appearance. In atypical cases, differential includes:

tracheobronchial diverticula
- different histologically : diverticula do not have normal bronchial wall morphology
necrotic / cavitating mass
- a consideration when associated lung parenchyma is atelectatic