Cystic Lung Diseases: Algorithmic Approach.

Cysts are commonly seen on CT scans of the lungs, and diagnosis can be challenging. Clinical and radiographic features combined with a multidisciplinary approach may help differentiate among various disease entities, allowing correct diagnosis. It is important to distinguish cysts from cavities because they each have distinct etiologies and associated clinical disorders. Conditions such as emphysema, and cystic bronchiectasis may also mimic cystic disease. A simplified classification of cysts is proposed. Cysts can occur in greater profusion in the subpleural areas, when they typically represent paraseptal emphysema, bullae, or honeycombing. Cysts that are present in the lung parenchyma but away from subpleural areas may be present without any other abnormalities on high-resolution CT scans. These are further categorized into solitary or multifocal/diffuse cysts. Solitary cysts may be incidentally discovered and may be an age related phenomenon or may be a remnant of prior trauma or infection. Multifocal/diffuse cysts can occur with lymphoid interstitial pneumonia, Birt-Hogg-Dubé syndrome, tracheobronchial papillomatosis, or primary and metastatic cancers. Multifocal/diffuse cysts may be associated with nodules (lymphoid interstitial pneumonia, light-chain deposition disease, amyloidosis, and Langerhans cell histiocytosis) or with ground-glass opacities (Pneumocystis jirovecii pneumonia and desquamative interstitial pneumonia). Using the results of the high-resolution CT scans as a starting point, and incorporating the patient's clinical history, physical examination, and laboratory findings, is likely to narrow the differential diagnosis of cystic lesions considerably.

Interpretation of plain chest roentgenogram.

Plain chest roentgenogram remains the most commonly ordered screening test for pulmonary disorders. Its lower sensitivity demands greater accuracy in interpretation. This greater accuracy can be achieved by adhering to an optimal and organized approach to interpretation. It is important for clinicians not to misread an abnormal chest radiograph (CXR) as normal. Clinicians can only acquire the confidence in making this determination if they read hundreds of normal CXRs. An individual should follow the same systematic approach to reading CXRs each time. All clinicians must make a concerted effort to read plain CXRs themselves first without reading the radiologist report and then discuss the findings with their radiology colleagues. Looking at the lateral CXR may shed light on 15% of the lung that is hidden from view on the posteroanterior film. Comparing prior films with the recent films is mandatory, when available, to confirm and/or extend differential diagnosis. This article outlines one of the many systematic approaches to interpreting CXRs and highlights the lesions that are commonly missed. A brief description of the limitations of CXR is also included.

Imaging of unusual diffuse lung diseases.

PURPOSE OF REVIEW: Computed tomography scans are commonly used in imaging lung diseases. As more information accumulates, patterns of rare or new diseases on CT scans are being increasingly reported. Several pulmonary diseases have distinguishing features, which are better delineated on high resolution CT scans than plain chest radiographs. The radiographic features of unusual diffuse lung diseases published in the past two years are described. RECENT FINDINGS: Severe acute respiratory syndrome generally manifests as focal or diffuse bilateral areas of consolidation on chest radiography and reticulation with ground-glass attenuation commonly seen on CT scans. A normal HRCT rules out the diagnosis of Pneumocystis carinii pneumonia while a normal chest radiograph does not. Immunocompromised patients without AIDS, who have CMV pneumonia, generally demonstrate a combination of ground-glass attenuation, air-space consolidation, and small nodules on HRCT. Nodules less than 10 mm in size in immunocompromised patients are highly suggestive of viral infections. Bronchial wall thickening on HRCT associated with cavitating nodules is suggestive of Wegner granulomatosis in the appropriate clinical setting. Small cysts may be seen in a minority of patients with subacute hypersensitivity pneumonitis and centrilobular emphysema in chronic farmer's lung. Reversed halo sign has a high specificity for cryptogenic organizing pneumonia. The triad of ground-glass opacities, ill-defined centrilobular nodules and cysts and focal areas of air trapping is highly suggestive of subacute hypersensitivity pneumonitis. SUMMARY: Familiarizing with radiographic and CT scan patterns may help the clinician to exclude certain diagnoses and narrow the differential diagnosis for others.