Lung changes in cystic fibrosis
In the classical presentation of cystic fibrosis (Cystic Fibrosis), imaging methods demonstrate steadily progressive involvement of the bronchial tree and pulmonary parenchyma.
A chest X-ray (CXR) shows pronounced bilateral bronchial wall thickening developing against the background of increased lung tissue lucency (hyperinflation). As the pathology progresses, advanced bronchiectasis (bronchiectasis) and areas of focal consolidation (nodular consolidation) are formed.
Computed tomography (CT) provides a more detailed picture:
- Bronchial wall thickening and the accumulation of thick secretions—mucous plugs (mucous plugging)—are clearly visualized.
- A characteristic background feature is mosaic attenuation of the parenchyma (mosaic attenuation).
- When an infectious component is added (e.g., an exacerbation caused by Mycobacterium abscessus), specific cavitating nodules (cavitating nodule) may be detected on tomograms.
| Method of examination | Main radiological signs | Additional findings |
|---|---|---|
| Radiography | Bronchial wall thickening, hyperinflation | Bronchiectasis, focal consolidation |
| CT | Mucous plugs, mosaic attenuation | Cavitating nodules (in infections) |
Pneumocystis Pneumonia
Pneumocystis pneumonia, caused by the microorganism Pneumocystis jiroveci (formerly known as Pneumocystis carinii), often manifests in immunocompromised states. The epidemiological peak of incidence in children occurs at 3–6 months of age—a critical period when the protective effect of transplacentally acquired maternal immunoglobulin G (IgG) wanes.
The classical radiological picture includes hyperinflation with diffuse bilateral interstitial or nodular infiltrates. It is important to note that in the early stages of the disease, changes may be extremely subtle. Diffuse perihilar granular shadowing (diffuse perihilar granular shadowing) is considered typical.
As the infectious process progresses, alveolar shadowing spreads rapidly. In severe cases, the radiological picture evolves into acute respiratory distress syndrome (ARDS / ARDS-type pattern) with total, widespread opacification of the lung fields (widespread opacification).
An important clinical feature of the course is that after successful therapy, radiological resolution (complete clearance of the lungs on imaging) significantly lags behind the patient's clinical improvement.
Invasive pulmonary aspergillosis (IPA)
Invasive pulmonary aspergillosis (Invasive pulmonary aspergillosis) develops as a result of hematogenous dissemination of an angioinvasive fungus. The pathogenetic basis is vascular obstruction by fungal emboli, which leads to tissue necrosis and the formation of hemorrhagic pulmonary infarction.
Radiological manifestations include multifocal areas of nodular or triangular parenchymal consolidation. On a standard radiograph, single or multiple nodules and masses (with or without cavitation) may be seen. However, radiography is often normal or may demonstrate a focal infiltrate visually indistinguishable from routine pyogenic pneumonia.
Specific signs are detected by high-resolution CT (HRCT):
- The «halo» sign (halo sign): represents a zone of decreased lung tissue attenuation in the form of ground-glass opacity (ground-glass attenuation). It forms a ring around the central fungal nodule or infarction and morphologically reflects the zone of perifocal necrosis and hemorrhage.
- The «air crescent» sign (air crescent sign): forms during cavitation of the lesion, when necrotic masses slough off and an air sickle is formed.
Rare manifestations include necrotizing pneumonia with infiltration of local structures. Despite the specific symptoms described, in many clinical cases the radiological picture remains nonspecific.
Non-infectious pulmonary complications
Immunocompromised patients frequently develop non-infectious complications, among which lymphoproliferative disorders (Lymphoproliferative disease - LPD) predominate. This is the most common type of neoplasia in immunodeficiencies, affecting not only the chest but also the abdominal cavity, soft tissues, and central nervous system.
The radiological picture of LPD in the chest is characterized by extreme variability. Diffuse or focal infiltrates, multiple or single parenchymal nodules, as well as mediastinal lymphadenopathy, which can reach giant proportions, are possible.
A frequent pulmonary manifestation of LPD is lymphocytic interstitial pneumonia (Lymphocytic interstitial pneumonia). Its pathomorphology is based on diffuse infiltration of the interstitium by plasma cells and lymphocytes (both polyclonal and monoclonal). Radiologically, this most frequently appears as an interstitial infiltrate affecting the basal and perihilar regions, or as discrete parenchymal nodules located along bronchovascular bundles.
Briefly: answers to topical questions
What forms of pulmonary aspergillosis are detected by diagnostic imaging in patients with cystic fibrosis and immunodeficiencies?
Diagnostic imaging in the cited sources describes the following forms of aspergillosis associated with cystic fibrosis and immunodeficiencies:
- Allergic bronchopulmonary aspergillosis (Allergic Bronchopulmonary Aspergillosis) — may occur in patients with cystic fibrosis. Radiological signs include nonsegmental areas of opacification, lobar atelectasis, mucous plugging, and branching tubular opacities resembling the «finger-in-glove» sign.
- Angioinvasive / invasive pulmonary aspergillosis (Angioinvasive / Invasive Pulmonary Aspergillosis) — occurs almost exclusively in immunocompromised individuals, mainly with severe neutropenia. CT describes multiple nodules with the «halo» sign, subpleural wedge-shaped areas of consolidation, and the «air crescent» sign.
What extrapulmonary manifestations of cystic fibrosis can be detected by ultrasound and abdominal CT?
According to the cited sources, ultrasound in patients with or suspected of having cystic fibrosis describes the following extrapulmonary manifestations:
- Hyperechoic bowel — is detected prenatally on ultrasound and is a clinical sign raising suspicion for cystic fibrosis.
- Meconium ileus — occurs in 15–20% of newborns with cystic fibrosis; in 90–95% of cases, its etiology is cystic fibrosis, therefore all patients with meconium ileus must be evaluated for cystic fibrosis.
- Intussusception — occurs in 1% of patients with cystic fibrosis, may present with recurrent abdominal pain, is diagnosed via ultrasound, and most commonly has an ileocolic localization.
Characteristic CT signs of abdominal manifestations of cystic fibrosis are not described in the cited sources.
To remember the specific CT symptoms of invasive aspergillosis, use the association with the sky: first, a lunar glow appears around the nodule—the «Halo» (hemorrhage), and then a cavity forms in the shape of a growing moon—the «Air crescent» (cavitation).
Class and exam questions
How does the radiographic pattern change with the progression of Pneumocystis pneumonia?
Initial perihilar granular shadowing rapidly evolves into an ARDS-like picture with widespread total opacification of the lung fields.
What does the "halo" sign on HRCT morphologically mean in aspergillosis?
The ground-glass opacity zone around the nodule arises due to perifocal necrosis and alveolar hemorrhage caused by fungal angioinvasion.
What else to study on this topic
- Pathogenesis and radiological differential diagnosis of bronchiectasis
- Acute respiratory distress syndrome (ARDS): radiological patterns
- Technique and indications for high-resolution CT (HRCT) of the lungs
- Morphological basis of the ground-glass opacity sign
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