Nonspecific interstitial pneumonia

Tomographic presentation of nonspecific interstitial pneumonia (NSIP)

High-resolution computed tomography (HRCT) serves as the primary tool for detecting nonspecific interstitial pneumonia. The radiological picture has several distinct patterns that allow differentiating this condition from other pulmonary parenchymal lesions.

• Dominant sign: presence of bilateral focal ground-glass opacities of the lung tissue (ground-glass opacification).
• Distribution of changes: the pathological process spreads uniformly throughout the lung volume. At the same time, a predominantly peribronchovascular localization is noted.
• Specific feature: the most important diagnostic criterion is the pronounced sparing, i.e., absolute preservation, of the subpleural regions of the lungs (subpleural sparing).

In addition to the main pattern, concomitant changes may be visualized on tomograms. These include mild reticular changes (mild reticulation) and the formation of mild traction bronchiectasis (traction bronchiectasis). The absence of severe deformation distinguishes this form from more severe fibrosing processes.

Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD)

Respiratory bronchiolitis-associated interstitial lung disease (Respiratory Bronchiolitis–Interstitial Lung Disease, RB-ILD) is closely associated with tobacco smoke exposure and is diagnosed predominantly in heavy smokers. The disease manifests insidiously, with the gradual onset of cough and progressive dyspnea (dyspnoea).

Classic chest radiography in this pathology has low diagnostic value. In almost 20% of patients, the radiograph remains completely normal.

HRCT reveals the following characteristic changes:

1. Distribution: the pathological process is localized predominantly in the upper lobes of the lungs.
2. Main pattern: focal ground-glass opacities, which are pathomorphologically caused by massive accumulation of macrophages in the lumens of alveoli and alveolar ducts.
3. Focal opacities: ill-defined centrilobular nodules of decreased density are formed. They have a typical "fluffy" (fluffy) appearance.

As additional signs, areas of "air trapping" (air trapping) indicating a bronchiolitic component of the lesion, and limited centrilobular emphysema of the upper lobes may be visualized. Scattered interlobular septal thickening and mild signs of interstitial fibrosis occur, but never act as the dominant pattern.

Desquamative interstitial pneumonia (DIP)

Desquamative interstitial pneumonia (Desquamative Interstitial Pneumonia, DIP) represents another variant of pulmonary parenchymal involvement. As with RB-ILD, standard chest radiography is often uninformative: up to 25% of patients have a normal radiological picture.

HRCT findings in DIP have their distinctive features:

• Leading symptom: extensive ground-glass opacity of the lung tissue.
• Localization: unlike RB-ILD, changes are typically concentrated in the lower zones of the lungs and have a peripheral distribution.
• Form of involvement: the pattern can be focal or form extensive "geographic" zones.

In a certain proportion of patients, signs of pulmonary fibrosis develop. This is manifested by disruption of normal lung architecture and dilatation (expansion) of some bronchi, although the extent of these changes usually remains limited.

General aspects of RB-ILD and DIP course

Respiratory bronchiolitis-ILD and desquamative interstitial pneumonia share a number of common clinical characteristics. First of all, both nosological forms can coexist in the same patient to varying degrees of severity, indicating the commonality of their pathogenetic mechanisms related to the pulmonary tissue reaction.

Most patients with a verified diagnosis of DIP or RB-ILD are characterized by a relatively stable clinical course without rapid deterioration of respiratory function. The most important, decisive role in the management of such patients is played by non-specific therapy—complete and unconditional smoking cessation (smoking cessation), which stops the progression of interstitial changes.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Pathomorphological substrate of the "ground-glass" sign during macrophage accumulation.
• Differential diagnosis of the "air trapping" pattern on HRCT.
• Mechanism of centrilobular emphysema formation in heavy smokers.
• Traction bronchiectasis: causes of formation in interstitial fibrosis.

Other topics in the «Chest Radiology» section

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