GGO in HRCT images is defined as ‘hazy increased attenuation of lung, but with preservation of bronchial and vascular margins’.14, 18 It is a non-specific finding and correlates histologically with partial filling of air spaces, inflammatory or fibrotic interstitial thickening, partial collapse of alveoli, or increased capillary blood volume.14, 18 Numerous disease processes can result in GGO as the sole or dominant finding in CT scans of the lung, including extrinsic allergic alveolitis, alveolar proteinosis, pulmonary oedema, and interstitial pneumonias.18 In chronic diffuse lung diseases GGO has been found to be a reliable indicator of inflammation in the absence of signs of fibrosis, a good prognostic factor, and in active diseases it is usually reversible.19, 20, 21