Cardiac bronchus

Last revised by Henry Knipe on 17 Aug 2023

A cardiac bronchus, sometimes termed accessory cardiac bronchus, is a rare anatomic variant of the tracheobronchial tree, arising from the medial aspect of the bronchus intermedius.

This anomaly is rare and is reported in ~0.3% (range 0.09-0.5%) of individuals 3-5. There may be a predilection for males. 

The vast majority of cardiac bronchi are asymptomatic. In some patients with lung parenchyma supplied by this bronchus, abnormal drainage predisposes them to recurrent chest infections 2. Hemoptysis 4 as well as cases of malignant transformation 6-9 have also been described.

The anomaly is thought to occur between the 4th and 6th 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 in size, morphology and length (range from 0.5-5 cm) 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 an amount of aerated lung parenchyma 1.

It is the only recognized true supernumerary bronchus, with other anomalies representing aplasia or abnormal branching patterns 3.

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

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

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

It is thought to be first described by R C Brock in 1946 11.

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

  • tracheobronchial diverticulum

    • different histologically: diverticula do not have normal bronchial wall morphology

  • bronchial laceration in trauma

    • almost always associated with other chest traumatic injuries

  • necrotic/cavitating mass

    • a consideration when associated lung parenchyma is atelectatic

  • owing to the possible complications mentioned above, the role of the radiologist is to both identify and report this rare anomaly

  • bronchoscopy may be indicated to differentiate the entity from a diverticulum 9

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Cases and figures

  • Figure 1: cardiac bronchus
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  • Case 1
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  • Case 2
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  • Case 3
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