A 3 year old female child developed fever, cough and respiratory distress. On chest x-ray consolidation is seen in right lower lobe. She improved with antibiotics but on follow up at 8 weeks was again found to have increasing consolidation in right lower lobe. Your next investigation would be:

C i.e., CT scan of chest Consolidation is an increase in parenchymal density obscuring margins of airways & vessles. It is a radiological sign of air space disease. (eg. pneumonia etc). CT scan is frequently requested in patients with air space disease and the CT features are occasionally diagnostic. In this child to rule out underlying predisposing lung pathology eg. pulmonary sequestration ect, CT scan would be the investigation of choice. Even in hypersensitivity pneumonitis (HP), high resolution CT has become the imaging procedure of choice. Lung biopsy (through flexible bronchoscope) may be diagnostic but not pathognomic. Traid of mononuclear bronchiolitis, interstitial infiltrates of plasma cells & lymphocytes and single non necrotizing randomly scattered parenchymal granuloma without mural vascular invasion is consistent with but specific for HP.