The "frosted glass" symptom is a non-specific radiological symptom that reflects various pathological changes in the lung tissue at the level of the alveoli . When computed tomography is visualized as a hazy, frosted decrease in the transparency of the lung tissue with a differentiated pattern of vessels and bronchi on this background. This symptom may be due to a partial decrease in the airiness of the pulmonary alveoli ( transudative , exudative, or other nature), their partial collapse ( hypoventilation ), or thickening of their walls. Since this symptom is not specific, it is necessary to keep in mind the anamnestic data, the clinical picture and the accompanying pathology. Due to the well-known subjectivity of assessing the presence of a frosted glass symptom, scan and visualization parameters should be considered; thus, a too narrow lung window creates a “spotting” of the image, distorting the true picture, and the low resolution and large slice thickness (more than 4 mm) create an averaging effect that conceals and erodes small details.
| Frosted Glass Symptom | |
|---|---|
 Patient with exogenous allergic alveolitis. Extensive areas of reduced airiness of the lung tissue of the "frosted glass" type, against which the "air traps" are defined. | |
| Research type | CT scan |
| Field of study | rib cage |
| Diseases | non-specific symptom |
Content
Distribution Types
Diffuse and focal changes
Pneumonia and pneumonitis of any etiology (bacterial, viral, fungal, etc.) are one of the most common causes of focal or diffuse frosted glass symptom, which may reflect either incomplete filling of the alveoli lumen (with initial or residual inflammatory manifestations), or infiltration of the alveolar walls (intralobular interstitium ). The focal areas of reduced airiness of the alveoli of the "frosted glass" type in bacterial pneumonia are more typical against the background of immunodeficiency, less often in immunocompetent patients [1] . A pattern of diffuse or diffuse mosaic "frosted glass", not accompanied by any other changes, may indicate Pneumonia . Cytomegalovirus pneumonia can also manifest itself only by this pattern, but can be supplemented by an expansion of the bronchi and thickening of their walls, areas of consolidation , often there is pleural effusion. Along with infectious pneumonitis, the symptom of diffuse "frosted glass" accompanies various variants of non-infectious lesions of the intralobular interstitium - idiopathic interstitial pneumonia , exogenous allergic alveolitis , etc.
In addition to the inflammatory process, a diffuse decrease in the airiness of the pulmonary tissue of the “frosted glass” type with thickening of the interlobular septa may be due to pulmonary edema , an acute post-transplant reaction. A similar CT scan can be detected in the acute phase of diffuse alveolar hemorrhage; the prevalence of “frosted glass” zones varies depending on the prevalence of hemorrhagic soaking.
Perifocal type
The “frosted glass” symptom may be noted around the foci of lung tissue consolidation (“ halo symptom ”). This picture was first described and considered typical for early invasive pulmonary aspergillosis , although it is not specific enough; Thus, cases of the symptom of aureole around infectious, malignant lesions of the lung are described. A similar pattern can be observed around “pseudo-foci” after a lung biopsy .
Mosaic type
A mosaic pattern of frosted glass distribution can be observed with infiltrative (inflammatory, hemorrhagic, etc.) changes in lung tissue, with uneven pulmonary perfusion due to chronic pulmonary artery pathology (for example, chronic thromboembolism ) or obstruction of terminal bronchial arteries ( obliterans of bronchial arteries ( obliteranshy ; bronchial asthma ). Differentiation of these conditions (in addition to the corresponding history and clinical picture) helps the analysis of the lung pattern on the background of a relatively more dense, "matte" tissue. With infiltrative changes, the lung pattern in adjacent areas is not significantly different; with obstructive or hypoperfusion changes, the lung pattern is relatively more enriched against the background of “frosted glass” areas (that is, in fact, unchanged lung tissue). Differentiate the presence of expiratory swelling of the lung tissue helps CT examination in the expiratory phase, which helps to identify "air traps".
Multiple clearly delimited areas of reduced airiness of the “frosted glass” type, against which there is a pronounced interstitium thickening, mostly interlobular, characteristic of alveolar lung proteinosis (this picture is called the symptom of “crazy striation” or “cobbled pavement”).
Sources
- Mitchellus, MD and Eric J. Stern, MD (inaccessible link) . Applied Radiology (1998). The appeal date is February 1, 2012. Archived May 18, 2012.
- Georgiadi SG, Kotlyarov PM Computer-tomographic signs of diffuse pulmonary diseases . Bulletin of the Russian Scientific Center for X-ray Radiology (2004). The appeal date is February 1, 2012. Archived May 18, 2012.
- M. Vogel, MD; H. Brodoefel, MD, T. Hierl, MD, R. Beck, MD, WA Bethge, MD, Claussen CD, PROF and MS Horger, MD. Differences and similarities of cytomegalovirus and pneumocystis pneumonia in HIV-negative immunocompromised patients - thin section CT morphology in the early phase of the disease . British Journal of Radiology (2006). The appeal date is February 1, 2012. Archived May 18, 2012.
Notes
- ↑ Hans-Ulrich Kauczor, MD Pneumonia in immunocompromized patients (the inaccessible reference is history ) . The appeal date is April 12, 2012.