High-resolution computerized tomography changes in diffuse parenchymal lung disease from chronic hypersensitivity pneumonitis related to bird antigen

Abstract

Background: Chronic hypersensitivity pneumonitis (HP) is the most common cause of diffuse parenchymal lung disease (DPLD) in India. There is no data regarding the avian antigen exposure-associated DPLD from the country.

Methods: Chronic HP from exposure to avian antigen was diagnosed when the high resolution computerized tomography (HRCT) showed features for HP and was supported by the history of exposure to pigeons, the presence of precipitin antibodies (IgG) to avian antigen in high titre with negative rheumatoid factor, antinuclear antibody, and no clinical clue for a collagen vascular disease. The HRCT changes were noted on Likert scale (0-5) in terms of affection of peripheral and/or axial involvement, reticulation, honeycombing, haze, mosaic, traction bronchiectasis, pleural reactions, features of pulmonary hypertension, and air cysts. Cardiomegaly and independent cardiac chamber enlargement were also recorded.

Results: The lower lobes were predominantly (65.6%) affected with similar frequency (78.1) of peripheral and axial parenchymal affection. The parenchymal changes in HRCT were haze or ground-glass opacity (100%), mosaic appearance (93.75%), reticulations (68.75%), traction bronchiectasis (34.3%), air cysts (21.8%), and honeycombing (9.37%). Pleural reactions, though not described so far, were found in 50% of cases. Features of pulmonary hypertension (87.5%), cardiomegaly (50%), left and right atrial enlargement (81.2% and 78.1%), and right ventricular enlargement (31.2%) were the common echocardiography findings.

Conclusion: Chronic HP from avian exposure shows predominantly lower lobe involvement with haze, reticulation, features of pulmonary hypertension, and pleural reactions as common HRCT findings. The likelihood of pulmonary hypertension appears high and although honeycombing is often present, the classical UIP pattern has not been found.

Keywords: Diffuse parenchymal lung disease; forced vital capacity; high-resolution computerized tomography; hypersensitivity pneumonitis.

Figure 1

Displays the relative status of the presence of the several morphological changes in terms of frequency and strength. LA, RA, RV represent left atrial, right atrial and right ventricle

Figure 2

High-resolution computerized tomography cut (transverse section) on the left shows extensive haze and mosaic appearance; the coronal section on the right shows the same involving predominantly upper lobe with the fissures been clearly visible where interlobular septal thickening and features of early fibrosis is accompanied in the lower lobe

Figure 3

On the left, there is predominantly pleural-based reticulations and also axial parenchymal thickening in the left upper lobe. There is a localized area of pleural-based haze (black arrow) with early reticulation and possibly some pleural thickening. The high-resolution computerized tomography section on the right shows interlobular septal thickening associated with reticulations and pleural reaction posteriorly (black arrow). The secondary lobules are seen to be hypodense or lucent from possible bronchiolar obstruction and air trapping (white arrow)

Figure 4

Thin section High resolution computerized tomography cut at the hilar level shows haze, areas of air trapping, and often nodular pleural thickening (see white arrow). The mediastinal border also looks spiky probably from some mediastinal pleural reactions. The pulmonary trunk in the section measures wider in diameter than the aorta suggesting the presence of pulmonary hypertension (see black arrowhead displays of the measurements)

Figure 5

High-resolution computerized tomography section shows diffuse haze, some granular appearance centrally around the bronchovascular bundles, air trapping, and cyst (see arrow)

Figure 6

High-resolution computerized tomography cut near the base shows cardiomegaly with enlargement of the right atrium (see an arrow with the outline delineated by the black line). The parenchyma shows haze, mosaic, reticulations, and prominent pulmonary artery branches