Granulomatosis with polyangiitis (Wegener Granulomatosis) Thoracic Imaging 

Updated: Oct 09, 2018
  • Author: James G Ravenel, MD; Chief Editor: Eugene C Lin, MD  more...
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Practice Essentials

Granulomatosis with polyangiitis (GPA), formerly known as Wegener granulomatosis, is a rare multisystem autoimmune disease of unknown etiology characterized by necrotizing granulomatous vasculitis of the upper and lower respiratory tract, glomerulonephritis, and small-vessel vasculitis of variable degree (classic Wegener granulomatosis). [1]

GPA is one of the ANCA-associated vasculitides (AAVs) and has a predilection for the upper and lower respiratory tracts and the kidneys. It has a spectrum of clinical presentations and may be divided broadly into limited or severe disease. Limited GPA presents with clinical findings largely isolated to the upper and lower respiratory tracts and is not considered an organ- or life-threatening disease. Severe disease presents with significant multisystem manifestations that may involve the lungs, kidneys, and other organs, in addition to the respiratory tract. Severe disease can also be described as generalized disease. [2]

Preferred examination

Because most patients have respiratory symptoms, chest radiographs are usually obtained first. These may be followed by computed tomography (CT) scans of the chest for better delineation of the abnormalities. Radiographic findings are nonspecific and include pulmonary nodules, fixed pulmonary infiltrates, and pulmonary cavities.

There are no diagnostic criteria for GPA. Diagnosis is based on a combination of clinical manifestations, positive ANCA serology, and histologic evidence of necrotizing vasculitis, necrotizing glomerulonephritis, or granulomatous inflammation from a relevant organ biopsy, such as skin, lung, or kidney. [1]  If the clinical findings are suggestive of GPA, further evaluation with biopsy or laboratory studies is required. [2, 3, 4]

The major limitation of radiographic techniques is the broad differential diagnosis of abnormalities in GPA. In addition, chest radiographic findings may be normal in as many as 20% of patients with the disease.

Lesions in GPA are gallium avid, as demonstrated in case reports. A negative gallium scan may be helpful in excluding active disease. [5]

(See the image below.)

Wegener granulomatosis, thoracic. Posteroanterior Wegener granulomatosis, thoracic. Posteroanterior chest radiograph in a middle-aged man with Wegener granulomatosis shows heterogeneous airspace opacity, which occurs predominately in the lower lobes, and a focal ill-defined opacity in the right upper lobe. Findings are suggestive of pulmonary hemorrhage.

Although the list of differential diagnoses and other problems is exceedingly broad and varied, the differential diagnosis can usually be limited by evaluating the radiographic findings in the context of the clinical history. Rheumatoid vasculitis (RV) is a major differential diagnosis. RV usually occurs in seropositive rheumatoid arthritis (RA) patients with longstanding disease. GPA lesions show necrotizing granulomatous vasculitis of small vessels, while the RV lesions mostly show leukocytoclastic vasculitis (LCV). Other differential diagnoses include pyoderma gangrenosum, lymphoma, tuberculosis, sarcoidosis and deep fungal infection.

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Radiography

Pulmonary nodules are the most common chest radiographic manifestation of GPA; they occur in 40-70% of cases. Nodules may be solitary or multiple; they are cavitated in as many as 50% of patients with nodules. Both thick- and thin-walled cavities may be present. Their size varies, ranging from 1.5-10 cm, and the nodules may wax and wane over time. Pneumothorax in association with cavitary nodules and subpleural blebs has been reported. [6, 7, 8]

Airspace opacities are a second manifestation of GPA. Usually, these findings involve a localized region of consolidation that may occasionally show central necrosis that mimics a lung abscess. Most frequently, this finding is the result of pulmonary hemorrhage, although pulmonary edema secondary to renal involvement may also occur. Over time, several of these opacities may evolve into thin-walled cavitary lesions. [6, 7, 8]

Other less common pulmonary manifestations include atelectasis and reticular interstitial opacities. Tracheal-bronchial abnormalities are rarely noted on chest radiographs, although tracheal stenosis may occasionally be visualized. Mediastinal adenopathy and pleural abnormalities are uncommon (< 10% of cases) and should prompt consideration of other diagnoses. [6, 7, 8]

(See the images below.)

Wegener granulomatosis, thoracic. Posteroanterior Wegener granulomatosis, thoracic. Posteroanterior chest radiograph in a middle-aged man with Wegener granulomatosis shows heterogeneous airspace opacity, which occurs predominately in the lower lobes, and a focal ill-defined opacity in the right upper lobe. Findings are suggestive of pulmonary hemorrhage.
Wegener granulomatosis, thoracic. Image obtained 4 Wegener granulomatosis, thoracic. Image obtained 4 months later in the same patient as in the previous image shows nearly complete resolution of lower lobe airspace disease, with partial resolution of the right upper lobe opacity. A new cavity is present in the left upper lobe.
Wegener granulomatosis, thoracic. Same patient as Wegener granulomatosis, thoracic. Same patient as in the previous 2 images. This radiograph was obtained 1 year after the image immediately previous to this one; it shows that the left upper lobe cavity has enlarged, without a change in wall thickness. Multiple new cavitary and noncavitary nodules are present in the right lung.
Wegener granulomatosis, thoracic. Thick-walled rig Wegener granulomatosis, thoracic. Thick-walled right upper lobe cavity in Wegener granulomatosis.
Wegener granulomatosis, thoracic. Wegener granulom Wegener granulomatosis, thoracic. Wegener granulomatosis is present as a single pulmonary mass. Chest radiograph shows a single right lower-lobe mass.

Because GPA is a rare disease, its appearance at the top of a differential diagnosis is unusual. Exceptions involve patients with sinusitis or renal disease and cavitary nodules or those with any of the mentioned radiographic findings and the appropriate clinical and laboratory findings. Most often, radiographs are helpful in confirming the diagnosis and in assessing the extent of pulmonary involvement.

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Computed Tomography

The major value of CT scanning is in the further characterization of lesions found on chest radiography, as well as in the depiction of unsuspected or radiographically occult abnormalities. Occasionally, CT scan findings are normal. As with chest radiographic findings, the predominant CT manifestations of GPA include pulmonary nodules with or without cavitation and airspace consolidation. [4]

(See the images below.)

Wegener granulomatosis, thoracic. CT scan shows a Wegener granulomatosis, thoracic. CT scan shows a well-circumscribed right lower-lobe mass. Biopsy revealed necrotizing granulomatous vasculitis, which is consistent with Wegener granulomatosis.
Wegener granulomatosis, thoracic. CT image obtaine Wegener granulomatosis, thoracic. CT image obtained with lung window settings shows a typical appearance of nodules in Wegener granulomatosis. Multiple ill-defined peripheral nodules have a halo with a ground-glass appearance. The halo is thought to represent adjacent pulmonary hemorrhage.

On CT, pulmonary nodules and masses range from 5 mm to 10 cm, and they are often cavitated. The lesions tend to be multiple and well defined, although the presence of more than 10 lesions is unusual. [9]

Airspace disease may include the following: (1) bilateral and diffuse disease caused by pulmonary hemorrhage, (2) scattered parenchymal disease with eventual coalescence of lesion, or (3) localized disease with ill-defined margins and air bronchograms or central cavitation. In the last case, the lesions may be surrounded by a halo of ground-glass opacity, which is the expression of alveolar hemorrhage.

Interstitial abnormalities are often present in GPA. They include interlobular septal thickening, parenchymal bands, and bronchial wall thickening. High-resolution CT (HRCT) scanning may be helpful in better defining these lesions. Pleural thickening, pleural effusion, and adenopathy may be present, but they are not usually associated with GPA.

Tracheobronchial abnormalities are better evaluated with CT than with other modalities. Although as many as 60% of patients with GPA have tracheobronchial abnormalities, no good data about the sensitivity and specificity of CT are available. In cases of suspected tracheobronchial involvement, thin, overlapping, axial sections with 2-dimensional and 3-dimensional reformations may provide better delineation of the length and degree of stenosis. These are particularly helpful when a tight stricture precludes the passage of a bronchoscope.

(See the image below.)

Wegener granulomatosis, thoracic. Three-dimensiona Wegener granulomatosis, thoracic. Three-dimensional shaded-surface display of the trachea shows eccentric narrowing of the subglottic trachea in this patient with airway involvement from Wegener granulomatosis.

Although nodules occur more frequently in patients with active disease and although parenchymal bands are more often seen in patients with quiescent disease, findings at various disease stages overlap considerably. Therefore, CT scan findings cannot be used to determine disease activity. CT scanning has greater utility in determining the response to corticosteroid and cytotoxic drug therapy. An increase in the size or number of parenchymal abnormalities suggests relapse, whereas decreasing nodule size, thickening of cavity walls, and increasing spiculation of lesions have all been described as improvement indications.

Diffuse Alveolar Hemorrhage (DAH) 

Granulomatosis with polyangiitis is a common cause of diffuse alveolar hemorrhage (DAH), representing 45% of the cases. DAH is defined by the presence of hemoptysis, diffuse alveolar infiltrates, and a decreased hematocrit level. HRCT features consist of bilateral ground-glass opacities and consolidations that are usually prominent in the perihilar areas, with a relative sparing of the subpleural pulmonary parenchyma, pulmonary apices, and costophrenic angles. The crazy paving pattern characterized by a smooth and regular interlobular septal thickening associated with ground-glass opacity may be seen days later in an acute episode of hemorrhage. [9]  

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Magnetic Resonance Imaging

The prevalence of myocardial involvement varies from 6 to 86% in GPA patients. [10]  Patients with myocardial involvement may have no symptoms or nonspecific symptoms, a normal ECG, and preserved left ventricular ejection fraction (LV-EF), but they may nevertheless face life-threatening arrhythmias or end-stage heart failure during the course of the disease. MRI may be useful in documenting myocardial lesions. [11]

Lesions may be diffuse or focal, involving the midventricular wall; they are not typical of patterns associated with myocardial ischemia. Cardiac MRI findings overlap with those of other nonischemic myocardial diseases, such as sarcoidosis and amyloidosis. MRI of the brain and/or spine should be considered in cases of extrapulmonary disease that potentially involves the central nervous system. [12]

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