Plastic bronchitis is characterized by marked obstruction of the large airways by bronchial casts. Bronchial casts take the shape of the bronchi of a lobe or a lung. These casts may result in mild symptoms or life-threatening disease, and diagnosis is usually made when casts are expectorated or removed by bronchoscopy.
Casts are often a complication of underlying bronchial diseases associated with mucus hypersecretion, such as cystic fibrosis, asthma, allergic bronchopulmonary aspergillosis, bronchiectasis or bronchopulmonary infections. Congenital and acquired cardiopathies have also been implicated in the formation of bronchial casts.
Nevertheless, this disorder has also been shown to occur in children with congenital cyanotic heart disease who have undergone cardiothoracic surgical procedures, most commonly the Fontan procedure.
In 1997, Seear, et al. separated bronchial casts into two well-defined groups as pathological:
- Type 1 (inflammatory) group, consisting of casts composed mainly of fibrin with a dense eosinophilic inflammatory infiltrate
- Type 2 (acellular) group, consisting of casts composed mainly of mucin with little or no cellular infiltrate, which occurs mostly in children with congenital cyanotic heart disease with palliative surgery.
Type 1 casts seem to be well controlled with bronchoscopic removal of the cast and steroid treatment, but treatment of type 2 casts has been more problematic; optimal treatment for patients with type 2 casts is not clear, unsuccessful, and the prognosis probably depends on the underlying cardiac status in this group.
Plastic bronchitis has also been shown to occcur in patients who have undergone cardiothoracic surgical procedures, most commonly the Fontan procedure. The Fontan procedure is performed on children with congenital single-ventricle heart disease and entails the diversion of systemic venous return into the pulmonary circulation. This operation has been associated with recurrent bronchial cast formation in 8 children reported in the last 15 years.
The mechanism by which this procedure predisposes children to cast is not obvious. Languepin, et al. explained a physiopathological mechanism for the formation of bronchial casts. Endobronchial lymphatic leakage, surgical trauma to the lymphatic channels surrounding the bronchi, pleural adhesions, lymphatic dysplasia and high systemic venous blood pressure are the principal factors resulting in the formation of bronchial casts in patients with cardiopathy.
Plastic bronchitis is reported to occur in patients who had developed chylothorax or pleuropericardial effusion a short time after their Fontan operation. Blood and lymph flow changes occur as a result of increased central venous pressure, and surgical trauma to the lymphatic channels surrounding the bronchi may be responsible for the occurrence of casts in these cases.
The Fontan operation causes an increase in systemic venous pressure in some cases, which not only obstructs lymph drainage from the thoracic duct, but also causes hepatic congestion, which significantly increases the volume of lymph in the thoracic duct. Some authors speculate that the formation of bronchial casts in children who have undergone the Fontan procedure is another manifestation of the unique univentricular circulation that predisposes these patients to third-space fluid loss; in particular, effusions, ascites, and peripheral edema are characterized by systemic venous hypertension. Ventricular systolic or diastolic dysfunction, atrioventricular valve insufficiency, and a variety of arrhythmias and protein-losing enteropathy are all reported to predispose a patient to and potentiate these problems.
Multiple treatment modalities have been used in the management of plastic bronchitis. Different therapies have been applied in various reports, depending on the nature of cast. Corticosteroids have been employed preferentially with type 1 casts, while bronchoscopic removal has been routinely practiced in most cases. Acetylcysteine, chest physiotherapy, systemic and inhaled corticosteroids, DNAse and aerosolized urokinase have all been used.
Though the optimal treatment for patients with type 2 casts is not clear; reducing venous pressure and improving cardiac output in children with underlying cardiac defects are considered important and potentially useful.
In our patient, the high systemic venous pressure arose from both the Fontan operation and left pulmonary artery occlusion, which improved via stent implantation in the left pulmonary artery. We hope that our experience will provide some help in the management of children with type 2 bronchial casts.
The above is an excerpt from a specific case study. You can read the study in its entirety here. Another similar study is also available here.