Thoracic Sarcoidosis: Imaging with High Resolution Computed Tomography.

INTRODUCTION: Sarcoidosis is a disease of unknown aetiology that primarily affects the lungs. Clinical and radiological findings with demonstration of non caseating granulomas on pathology is utilised for diagnosing the disease.

AIM: To assess and evaluate the features of thoracic sarcoidosis on High Resolution Computed Tomography (HRCT) chest.

MATERIALS AND METHODS: A total of 40 (31 males and 9 females) cases of pulmonary sarcoidosis in a period of three years were included in this study. Patients underwent detailed clinical evaluation, imaging, Pulmonary Function Tests (PFT) and pathological confirmation of disease. Chest radiograph was obtained in all patients. HRCT was done on 16 slice Computed Tomography (CT) using 1 mm slice thickness and high spatial frequency algorithm for image re-construction. Images were viewed and evaluated using appropriate lung and mediastinal windows. The lymph nodes were classified as hilar and mediastinal with Maximum Short Axis Diameter (MSAD) more than 10 mm taken as cut-off for enlargement. Pulmonary opacities were classified as nodules (micronodules 1-4 mm and macronodules >5 mm), reticular opacities, fibrotic lesions, ground glass opacities and consolidations. Nodule distribution classified as perilymphatic centrilobular and random. Repeat scanning done on follow up or as clinically indicated.

RESULTS: A total of five patients had Stage I disease, 24 patients had Stage II disease, eight patients had Stage III disease and three patients had stage IV disease. Mediastinal lymphdenopathy present in 29 patients. Bilateral hilar adenopathy was the predominant pattern seen in 22 patients. Lung parenchymal lesions excluding end stage disease noted in 32 patients. The characteristic HRCT lung parenchymal involvement of micronodules with a perilymphatic distribution was seen in 26 patients. HRCT features of predominant upper and middle lobe distribution seen in majority of patients. Documented atypical lesions and the characteristic features of end stage lung disease on HRCT noted in a small subset of patients. HRCT was superior to chest radiography for evaluating the features, pattern and distribution of the parenchymal lesions and mediastinal lymph nodes, for assessing the stage and activity of the disease and in aiding detection of subtle parenchymal lesions which are liable to be missed on conventional imaging.

CONCLUSION: Thoracic sarcoidosis can have varied presentations. HRCT is superior to conventional CT for the detection and characterisation of the lung parenchymal lesions.