On HRCT, ground-glass opacities are peripherally distributed, with some opacities appearing in the posterior (dependent) segments of the lower lobes of the lungs. There is no radiographic evidence of recurrent aspiration, lung cancer, or pleural effusion.
A common radiographic pattern of nonspecific interstitial pneumonia (NSIP), which is common in SSc-associated ILD. A usual interstitial pneumonia (UIP) pattern, characterised by honeycombing and bronchiectasis, may also be seen. Since the HRCT pattern predicts the underlying histopathology well, a lung biopsy is not generally necessary.
Complete lung function testing (spirometry, lung volume, and diffusing capacity) is also ordered, as these values should be obtained in the workup of most patients with suspected ILD.
Pulmonary Function Testing
Most ILDs are characterized by reductions in total lung capacity, functional residual capacity, and residual volume. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) are also decreased in ILD, but usually the changes are in proportion to the decreased total lung volume. Thus, the FEV1/FVC ratio is usually normal or even increased. This is in sharp contrast to an obstructive pattern found on pulmonary function testing, with a reduced FEV1/FVC ratio; this pattern is found with sarcoidosis, combined chronic obstructive pulmonary disease (COPD) and ILD, and hypersensitivity pneumonitis.
The diffusing capacity for carbon monoxide (DLCO) is often low in ILD, due to the alveolar ventilation-perfusion mismatch; however, this finding is nonspecific.DLCO is an important functional test due to its ability to evaluate the interstitial space between alveolar and endothelial surfaces.
DLCO can be reduced either in parenchymal fibrosis or in vascular abnormalities of pulmonary hypertension (PH). In general, the severity of the DLCO reduction does not correlate exactly with disease prognosis, unless it is rapidly declining or <35% of the predicted value. DLCO provides a good estimate of the extent of ILD on HRCT.
You now would like to order an echocardiogram to rule out PH, as it is the most common pulmonary vascular disease in SSc.