Post-infectious bronchiolitis obliterans in children: CT features that predict responsiveness to pulse methylprednisolone

Objective:

Intravenous pulse methylprednisolone therapy (IPMT) is an important treatment option for post-infectious obliterative bronchiolitis (OB), although it must be used carefully and only in selected patients because of its drawbacks. This study evaluated whether CT and clinical features of children with post-infectious OB can predict their responsiveness to IPMT.

Methods:

We searched the medical records for patients (less than 18 years of age) who were diagnosed with post-infectious OB between January 2000 and December 2011. 17 children who received IPMT were included in this study. All underwent chest CT before and after IPMT. The radiological features seen on pre-treatment CT were recorded. The air-trapping area percentages on pre- and post-treatment CT images were determined. The nine patients who exhibited decreased air trapping on post-treatment CT scans relative to pre-treatment scans were classed as responders. The patient ages and time from initial pneumonia to IPMT were recorded.

Results:

All responders and only four non-responders had thickened bronchial walls before treatment (p = 0.029). The two groups did not differ significantly in terms of bronchiolitis, bronchiectasis or the extent of air trapping, although the responders had a significantly shorter median interval between initial pneumonia and IPMT (4 vs 50 months; p = 0.005) and were significantly younger (median, 2.0 vs 7.5 years; p = 0.048).

Conclusion:

Immediate IPMT may improve the degree of air trapping in children with post-infectious OB if they show a thickened bronchial wall on CT.

Advances in knowledge:

Children with post-infectious OB may respond favourably to IPMT when pre-treatment CT indicates bronchial-wall thickening.Post-infectious obliterative bronchiolitis (OB) is an uncommon and severe form of chronic obstructive lung disease that follows a microbiological insult to the lower respiratory tract. At the pathological level, it is characterized by a fibrosing inflammatory process around the lumen of the bronchioles that results in concentric narrowing and obliteration of the small airways.^1,2 Consequently, areas of hypoventilation with air trapping, bronchiectasis and atelectasis can develop.³ The clinical severity of post-infectious OB correlates with the degree of air trapping and the amount of inflammation. The prognosis is not favourable, and the prospective observational study of Zhang et al⁴ of 31 post-infectious OB cases revealed that while clinical remission occurred in 22.6%, persistent respiratory signs and symptoms occurred in 67.7% and 9.7% died.Post-infectious OB is considered to be an irreversible airway obstruction; thus the principal treatment is supportive. Important general supportive treatment options include avoidance of second-hand smoking and other inhaled irritants, annual influenza vaccination, airway clearance techniques, adequate nutritional intake and supplemental oxygen for patients with hypoxaemia. A drug that may be effective is azithromycin, a microlide antibiotic, and although its usefulness in post-infectious OB has not been tested, it is effective in other chronic obstructive diseases, including diffuse panbronchiolitis and cystic fibrosis, and in OB syndrome after lung or bone marrow transplantation.^5–8 Inhaled corticosteroids and bronchodilators are also recommended for patients whose airway obstruction is improved after using bronchodilators. Systemic corticosteroids are also frequently used, although their effectiveness in improving the outcome in patients with post-infectious OB is as yet unknown. Intravenous pulse methylprednisolone therapy (IPMT) is currently the preferred method of treatment. However, this approach necessitates frequent hospital admissions during treatment and has high rates of side effects. For this reason, IPMT must be used with care and only in selected patients with post-infectious OB.^2,5CT is an effective and widely used, non-invasive method for confirming the diagnosis of post-infectious OB, as it is more sensitive than chest radiography. We hypothesized that it might be possible to predict a patient''s responsiveness to IPMT by analysing pre-treatment CT findings, thereby reducing the risk of unfavourable side effects from IPMT. Therefore, the purpose of this study was to evaluate whether CT and clinical features of children with post-infectious OB are predictive of their responsiveness to IPMT.