Introduction	Choose Top of pageABSTRACTIntroduction <<Nodules and MassesGround-Glass Opacity to L...Airway InvolvementConclusionReferencesCITING ARTICLES

Wegener's granulomatosis is a multisystemic necrotizing vasculitis first described by German pathologist Friedrich Wegener in 1936 [1]. Wegener's granulomatosis most commonly occurs in whites and affects men and women equally. The mean age at diagnosis is 40 years, but the disease can develop at any age. The upper respiratory tract is affected in almost all patients, and the lungs and kidneys are involved in 90% and 80% of patients, respectively [2]. Other organs less commonly affected include the central and peripheral nervous system, spleen, and large joints.

Patients may present with respiratory signs and symptoms, including cough, hemoptysis, and dyspnea. Elevation of serum c-antineutrophil antibodies against protease 3 in cytoplasmic granules (c-ANCA) titers frequently occurs in patients with Wegener's granulomatosis and can be used to assess disease activity [3]. The reference standard for diagnosis is biopsy. Renal biopsy, the most common approach, usually shows a nonspecific glomerulonephritis. Lung biopsy may show a granulomatous small-vessel necrotizing vasculitis [2].

Treatment includes immunosuppressant therapy, most commonly systemic steroids and cyclophosphamide. Remission rates are approximately 90%, but relapses may occur. Resolution of imaging findings of Wegener's granulomatosis may lag behind clinical improvement [4].

Nodules and Masses	Choose Top of pageABSTRACTIntroductionNodules and Masses <<Ground-Glass Opacity to L...Airway InvolvementConclusionReferencesCITING ARTICLES

Lung nodules are the most common manifestation of Wegener's granulomatosis and occur in approximately 40–70% of patients [3, 4] (Fig. 1). Nodules are usually multiple and bilateral and occur without a zonal predilection. The size of Wegener's granulomatosis nodules varies, most commonly measuring between 2 and 4 cm but ranging from a few millimeters to 10 cm [5]. Wegener's granulomatosis nodules may occur in a centrilobular distribution (Figs. 2A and 2B), mimicking tuberculosis, hypersensitivity pneumonitis, or an acute viral, bacterial (Fig. 3), or fungal pneumonia. Cavitation occurs in approximately 25% of nodules larger than 2 cm [3, 4]; the walls of the cavities may be thin or thick and nodular (Figs. 4A, 4B, and 5). Wegener's granulomatosis nodules and cavities may be easily mistaken for metastases, lung abscesses, or septic infarcts (Figs. 6A and 6B). As with any lung cavity, those occurring in Wegener's granulomatosis may become secondarily infected (Figs. 7A and 7B), in which case gas–liquid levels may develop. Hemorrhage may occur around nodules and manifests on high-resolution CT as ground-glass opacity surrounding the consolidated nodule, referred to as the halo sign [6] (Figs. 8A and 8B). The halo sign may also be seen with lesions in surrounding hemorrhage or cellular infiltration, such as bronchioloalveolar carcinoma and hypervascular metastases, and in angioinvasive infection such as Aspergillus fumigatus. A “reverse halo sign” may also occur in Wegener's granulomatosis (Fig. 9), presumably reflecting an organizing pneumonia reaction in the periphery of focal hemorrhage.

Ground-Glass Opacity to Lung Consolidation: The Spectrum	Choose Top of pageABSTRACTIntroductionNodules and MassesGround-Glass Opacity to L... <<Airway InvolvementConclusionReferencesCITING ARTICLES

Lung consolidation and ground-glass opacity often occur in approximately 30% of patients with active Wegener's granulomatosis and are usually the result of hemorrhage [7] (Figs. 10A, 10B, 11A, 11B, 12A, and 12B). When present in isolation, lung consolidation is often initially attributed to pneumonia, and Wegener's granulomatosis may be diagnosed when consolidation persists despite appropriate treatment. Arteriolar involvement with Wegener's granulomatosis may present as mosaic attenuation or tree-in-bud opacities [8].

Ground-glass opacity in Wegener's granulomatosis may be the result of alveolar hemorrhage, necrotic cellular infiltrate in the alveoli, or mosaic perfusion secondary to small-vessel vasculitis. Diffuse alveolar hemorrhage occurs in approximately 10% of patients with Wegener's granulomatosis [9, 10]. The primary high-resolution CT finding of diffuse alveolar hemorrhage is diffuse ground-glass opacity, often with sparing of the subpleural lung. Interlobular septal thickening may result from congestion of lymphatics or aggregation of hemosiderin-laden macrophages. Areas of diffuse hemorrhage may coalesce to form hemorrhagic consolidation (Figs. 13, 14A, and 14B). Consolidation in Wegener's granulomatosis also may be secondary to pulmonary infarcts or organizing pneumonia [4]. These findings may mimic bacterial, viral, or fungal pneumonia; tuberculosis; pulmonary edema; acute respiratory distress syndrome (ARDS); or bronchioloalveolar carcinoma.

Airway Involvement	Choose Top of pageABSTRACTIntroductionNodules and MassesGround-Glass Opacity to L...Airway Involvement <<ConclusionReferencesCITING ARTICLES

Airway involvement is a late complication of Wegener's granulomatosis that occurs in 15–25% of patients. Patients may present with progressive respiratory difficulty and stridor [11]. The distribution may be focal or diffuse; the subglottic trachea is most commonly involved, with an incidence of 16–23% [12–14] (Figs. 15A and 15B). One series of 77 patients with Wegener's granulomatosis reported an incidence of bronchial stenosis of 18% [9]. Concentric wall thickening may lead to airway stenosis, which may be circumferential or irregular. Mucosal ulceration may also occur and can result in hemoptysis. Virtual bronchoscopy is a useful tool to further characterize bronchial stenoses, particularly in the central airways [15] (Figs. 16A, 16B, 16C, 17A, 17B, and 17C). Virtual bronchoscopy is complementary to fiberoptic bronchoscopy, with a sensitivity of 80% for airway involvement [11]. Airway involvement in Wegener's granulomatosis can mimic tracheobronchial tumors such as adenoid cystic carcinoma as well as tracheal amyloidosis and stenosis from prolonged intubation (Fig. 18) or tuberculosis.

Conclusion	Choose Top of pageABSTRACTIntroductionNodules and MassesGround-Glass Opacity to L...Airway InvolvementConclusion <<ReferencesCITING ARTICLES

The spectrum of high-resolution CT findings of Wegener's granulomatosis is broad, ranging from nodules and masses to ground-glass opacity and lung consolidation. Airway involvement may be focal or extensive. The high-resolution CT findings of Wegener's granulomatosis may mimic other conditions such as pneumonia, neoplasm, and noninfectious inflammatory diseases. Although Wegener's granulomatosis is an uncommon disease, recognition of its pulmonary and airway manifestations may help suggest the diagnosis when it is unsuspected.

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Fig. 1 —66-year-old man with active Wegener's granulomatosis. Unenhanced CT image shows right lower lobe nodule with central low attenuation (arrow).

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Fig. 2A —43-year-old man with active Wegener's granulomatosis. High-resolution CT images through right lung show centrilobular ground-glass attenuation nodules (arrows) and larger subpleural ground-glass nodule (arrowhead, A).

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Fig. 2B —43-year-old man with active Wegener's granulomatosis. High-resolution CT images through right lung show centrilobular ground-glass attenuation nodules (arrows) and larger subpleural ground-glass nodule (arrowhead, A).

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Fig. 3 —34-year-old woman undergoing immunosuppression for Wegener's granulomatosis with Haemophilus influenzae. High-resolution CT image of left lung shows clusters of centrilobular nodules (arrow) and thickening of adjacent bronchial walls.

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Fig. 4A —49-year-old man with active Wegener's granulomatosis and epistaxis. High-resolution CT image through upper lobes shows large nodules with lobulated and spiculated margins.

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Fig. 4B —49-year-old man with active Wegener's granulomatosis and epistaxis. Three months later, nodules have cavitated, as shown on this high-resolution CT image.

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Fig. 5 —37-year-old woman with resolving flare-up of Wegener's granulomatosis. High-resolution CT image shows single cavity with relatively thin wall and small septation (arrow) in left lower lobe.

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Fig. 6A —39-year-old man with septic infarcts from bacterial endocarditis. Transverse and coronal high-resolution CT images show multiple cavitary and noncavitary nodules and consolidation with peripheral and basal predominance in both lungs.

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Fig. 6B —39-year-old man with septic infarcts from bacterial endocarditis. Transverse and coronal high-resolution CT images show multiple cavitary and noncavitary nodules and consolidation with peripheral and basal predominance in both lungs.

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Fig. 7A —35-year-old man with Wegener's granulomatosis on chronic immunosuppressants and Aspergillus fumigatus superinfection. Coronal high-resolution CT image shows large Wegener's granulomatosis cavity (arrow) superinfected and Aspergillus fumigatus. Other cavities in left lung are related to Wegener's granulomatosis alone.

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Fig. 7B —35-year-old man with Wegener's granulomatosis on chronic immunosuppressants and Aspergillus fumigatus superinfection. Coronal high-resolution CT image obtained after cessation of immunosuppressant therapy and initiation of antifungal therapy shows decrease in cavity (arrow) caused by Aspergillus fumigatus but enlargement of Wegener's granulomatosis cavities in left lung.

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Fig. 8A —26-year-old woman with active Wegener's granulomatosis. Transverse high-resolution CT image shows cavitary nodule in right lung (arrow).

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Fig. 8B —26-year-old woman with active Wegener's granulomatosis. Sagittal high-resolution CT image shows cavity crossing major fissure (arrowheads) and halo of ground-glass opacity surrounding nodule, representing hemorrhage.

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Fig. 9 —51-year-old man with active Wegener's granulomatosis. High-resolution CT image shows right upper lobe ground-glass attenuation nodule with thin rim of peripheral consolidation or “reverse halo” (arrow) and small foci of ground-glass opacity in left upper lobe (arrowheads).

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Fig. 10A —42-year-old woman with active Wegener's granulomatosis. Transverse (A) and coronal (B) high-resolution CT images show patchy ground-glass opacity in both lungs from alveolar hemorrhage.

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Fig. 10B —42-year-old woman with active Wegener's granulomatosis. Transverse (A) and coronal (B) high-resolution CT images show patchy ground-glass opacity in both lungs from alveolar hemorrhage.

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Fig. 11A —59-year-old woman with Wegener's granulomatosis and hypoxia. High-resolution CT images show patchy peribronchial and peripheral ground-glass opacity resulting from active vasculitis.

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Fig. 11B —59-year-old woman with Wegener's granulomatosis and hypoxia. High-resolution CT images show patchy peribronchial and peripheral ground-glass opacity resulting from active vasculitis.

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Fig. 12A —63-year-old woman with active Wegener's granulomatosis. High-resolution CT images show patchy peripheral and peribronchial lung consolidation with air bronchograms.

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Fig. 12B —63-year-old woman with active Wegener's granulomatosis. High-resolution CT images show patchy peripheral and peribronchial lung consolidation with air bronchograms.

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Fig. 13 —61-year-old man with hypertension, dyspnea, and renal insufficiency. High-resolution CT image shows extensive ground-glass opacity and consolidation with relative subpleural sparing representing diffuse alveolar hemorrhage. Elevated c-ANCA (c-antineutrophil antibodies against protease 3 in cytoplasmic granules) levels and subsequent renal biopsy confirmed diagnosis of Wegener's granulomatosis.

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Fig. 14A —63-year-old man who presented to emergency department in respiratory distress. Transverse and coronal high-resolution CT images show ground-glass opacity with interlobular septal thickening and patchy consolidation throughout both lungs. Renal biopsy confirmed diagnosis of Wegener's granulomatosis.

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Fig. 14B —63-year-old man who presented to emergency department in respiratory distress. Transverse and coronal high-resolution CT images show ground-glass opacity with interlobular septal thickening and patchy consolidation throughout both lungs. Renal biopsy confirmed diagnosis of Wegener's granulomatosis.

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Fig. 15A —46-year-old man with Wegener's granulomatosis presenting with dyspnea and stridor. Transverse and sagittal CT images show eccentric narrowing of subglottic trachea (arrows).

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Fig. 15B —46-year-old man with Wegener's granulomatosis presenting with dyspnea and stridor. Transverse and sagittal CT images show eccentric narrowing of subglottic trachea (arrows).

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Fig. 16A —34-year-old woman with Wegener's granulomatosis and progressive dyspnea, wheezing, and stridor. Unenhanced CT image shows eccentric mural thickening (arrow) and mild stenosis of upper thoracic trachea.

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Fig. 16B —34-year-old woman with Wegener's granulomatosis and progressive dyspnea, wheezing, and stridor. Coronal oblique reconstruction shows long-segment irregular narrowing of trachea (arrow) and mild narrowing of left main bronchus (arrowhead).

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Fig. 16C —34-year-old woman with Wegener's granulomatosis and progressive dyspnea, wheezing, and stridor. Virtual bronchoscopic image shows mid tracheal thickening (arrow) and stenosis corresponding to lesion in B.

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Fig. 17A —51-year-old woman with long-standing Wegener's granulomatosis. Unenhanced CT image shows concentric thickening of right main bronchus wall (arrow) and mild luminal stenosis.

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Fig. 17B —51-year-old woman with long-standing Wegener's granulomatosis. Transverse minimum-intensity-projection image shows marked stenosis of proximal right middle lobe bronchus (arrow).

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Fig. 17C —51-year-old woman with long-standing Wegener's granulomatosis. Virtual bronchoscopic image shows narrowing of orifice of right middle lobe bronchus (arrow).

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Fig. 18 —52-year-old man with tracheal stenosis from prolonged endotracheal intubation. CT sagittal reconstruction shows focal subglottic tracheal narrowing (arrow).