In nonfibrotic HP, HRCT findings consist of areas of ground-glass opacity and ill-defined, small centrilobular faint opacities on inspiratory scans. These findings are diffusely distributed in the bilateral lung fields. Fibrotic HP has CT diagnostic criteria in HP clinical practice guidelines. A three-density pattern, which means an admixture of high or low attenuated lobules and normal ones, is commonly seen in fibrotic HP.