Aspergillosis, Angioinvasive



Aspergillosis, Angioinvasive


Helen T. Winer-Muram, MD





Key Facts


Terminology



  • Invasive aspergillosis: Tissue invasion either angioinvasive or airway invasive, typically occurs in patients with neutropenia or impaired neutrophil function


Imaging Findings



  • Nodules, single or multiple


  • Hypodense sign: Central hypodensity, due to infarction


  • Halo sign: Large bull’s eye surrounded by smaller rim ground-glass opacification



    • Ground-glass attenuation corresponds to rim of hemorrhage


  • CT angiogram sign: Vessels cut off at edge of nodule


  • Air crescent sign, late sign, follows recovery of neutrophils


Top Differential Diagnoses



  • Halo Sign



    • Mucormycosis


    • Tuberculosis


    • Bacterial Abscess


    • Metastases: Angiosarcoma


Pathology



  • Hyphae invade vessels or airway walls causing occlusion


  • 60% of fungal pneumonias in immunocompromised patients are caused by Aspergillus


Clinical Issues



  • Neutropenia main risk factor


  • Surgery may be indicated in some patients, particularly for treatment of massive hemoptysis







Axial CECT shows a typical appearance of the halo sign with large round foci of dense consolidation image and peripheral ground-glass opacity image.






Axial HRCT shows the typical appearance of air crescent sign image. Infarcted lung is adherent to normal lung medially image. The “lung ball” is not mobile in the cavity.


TERMINOLOGY


Abbreviations and Synonyms



  • Invasive pulmonary aspergillosis (IPA), chronic necrotizing pulmonary aspergillosis = semi-invasive aspergillosis


Definitions



  • Invasive pulmonary aspergillosis



    • Tissue invasion, either angioinvasive or airway invasive; typically occurs in patients with neutropenia or impaired neutrophil function


  • Semi-invasive aspergillosis



    • Indolent pulmonary infection in mildly immunocompromised patients



      • Prolonged corticosteroids, malignancy, diabetes, alcoholism, sarcoidosis


IMAGING FINDINGS


General Features



  • Best diagnostic clue: Fulminant lung disease in febrile neutropenic patient


  • Patient position/location



    • Invasive aspergillosis, no lobar predilection


    • Semi-invasive aspergillosis, upper lobes


  • Size: Nodule(s) from 6 mm to 3 cm


  • Morphology: Mass(es), consolidation with central hypodense sign or halo sign


CT Findings



  • Angioinvasive



    • Nodules, single or multiple, typically < 10 in number



      • 6 mm to 3 cm


    • Hypodense sign, early sign



      • Central hypodensity in nodule or consolidation, due to infarction


      • Usually more than 50% of lesion


    • Halo sign, early sign



      • Mass-like lung consolidation or nodules surrounded by ground-glass attenuation


      • Bull’s eye larger than halo


      • Very suggestive of invasive aspergillosis in immunocompromised patient


      • Warrants starting antifungal therapy before confirmation with other tests



    • CT angiogram sign



      • Interruption of peripheral segmental artery at edge of nodule


      • Vessel not visible in lesion


      • Best demonstrated on MIP reconstructions


    • Air crescent sign, late sign



      • Crescentic and eventual circumferential cavitation


      • Fragments of infarcted lung separate from adjacent parenchyma (pulmonary sequestra)


      • Has limited utility for diagnosis, seen in up to 50%


      • Occurs during convalescence and recovery of neutrophil count, typically 2-3 weeks after therapy started


      • May evolve to reassemble aspergilloma or thin-walled cyst


      • Typically close in 2-3 weeks


    • Consolidation



      • Pleural-based wedge-shaped consolidation similar to infarct


      • May also show hypodense sign


    • May traverse fascial planes, invading pleura, chest wall, pulmonary artery, pericardium, heart, mediastinum


  • Airway invasive aspergillosis



    • Less common than angioinvasive (30%)


    • Centrilobular nodules, tree-in-bud opacities


    • Consolidation centered on airways (peribronchial)


    • Invasive tracheobronchial aspergillosis



      • Ulcerations of trachea and central bronchi


      • Can be associated with atelectasis and consolidation


      • Sometimes seen in lung transplant recipients


  • Semi-invasive aspergillus



    • Varied appearance, may present as slowly growing nodule or focus of consolidation at lung apex, mimics post-primary tuberculosis


    • Progressive upper lobe cavitary consolidation, pleural thickening


    • An aspergilloma can be present


    • Associated with preexisting pulmonary emphysema


  • Pleural effusion, 10%


  • May show hypodensities in liver, spleen, or kidneys, indicating disseminated disease


Radiographic Findings



  • Findings often nonspecific, new focal or multifocal abnormalities best investigated with CT


  • Invasive pulmonary aspergillosis



    • Initially, chest radiograph can be normal


    • Lung nodules or areas of consolidation can progress rapidly


    • Air crescent sign



      • Crescent-shaped gas collection within pulmonary nodule or consolidation


      • Can progress to extensive cavitation and necrosis


    • Can invade pleural space, causing empyema or pneumothorax


  • Semi-invasive aspergillosis



    • Mimics post-primary tuberculosis


Imaging Recommendations



  • Best imaging tool: HRCT best to show central necrosis, halo sign, air crescent sign


  • Protocol advice: MIP reconstructions for angioinvasion


DIFFERENTIAL DIAGNOSIS


Halo Sign

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Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Aspergillosis, Angioinvasive

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