Pulmonary Aspergillosis: What CT can Offer Before it is too Late!

Abstract

Aspergillus is a large genus of saprophytic fungi which are present everywhere in the environment. However, in persons with underlying weakened immune response this innocent bystander can cause fatal illness if timely diagnosis and management is not done. Chest infection is the most common infection caused by Aspergillus in human beings. Radiological investigations particularly Computed Tomography (CT) provides the easiest, rapid and decision making information where tissue diagnosis and culture may be difficult and time-consuming. This article explores the crucial role of CT and offers a bird's eye view of all the radiological patterns encountered in pulmonary aspergillosis viewed in the context of the immune derangement associated with it.

Keywords: Air-crescent; Fungal ball; Halo sign; Invasive aspergillosis.

[Table/Fig-1]:

Schematic diagram showing spectrum of pulmonary aspergillosis with respect to host immune status.

[Table/Fig-2]:

CECT thorax of a 42-year-old asthmatic female on chronic steroid therapy showing: (a) Left lower lobe nodule with air-bronchogram surrounded by the halo sign and centrilobular nodules (black arrow), (b) One nodule (while arrow) in the right upper lobe associated with an ectatic bronchus and another smaller nodule adjacent to the wall of the bronchus; Hyphae of A. fumigatus obtained through a bronchoalveolar lavage of the same patient seen in (c) Calcofluor white stain; and (d) PAS stain showing acute angled branching, hyaline, septate hyphae.

[Table/Fig-3]:

Angioinvasive aspergillosis in a 35-year-old male patient who underwent bone marrow transplant whose sputum examination demonstrated actively multiplying colonies of Aspergillus fumigatus Serum was also positive for galactomannan. CT thorax done (a) at presentation showing patchy consolidation with surrounding ground glass opacity (Halo sign, depicted by arrowheads) in right lower lobe and (b) after 14 days showing breakdown with air-crescent formation (arrows) within the consolidation.

[Table/Fig-4]:

(a) Plain radiograph posteroanterior view chest of a 56-year-old female patient on cancer chemotherapy showing consolidation-cavitation with air crescent in right upper lobe suggestive of fungal ball with possibly invasion. (b) CT thorax of another 29-year-old male patient with angioinvasive aspergillosis who underwent a renal transplant showing a nodular lesion in left lung with central hypodensity (arrows). The “Hypodense sign” preceding the formation of air crescent is a less sensitive but highly specific sign for fungal infection.

[Table/Fig-5]:

Fungal bronchopneumonia of the airway, invasive variety in a 38 years old patient with AIDS. CT thorax demonstrates multifocal areas of nodular consolidation and surrounding ground glass opacities (arrows). Diffuse centrilobular nodules with branching linear and nodular areas (arrowheads) distributed throughout the lungs.

[Table/Fig-6a-d]:

(a,b) Chronic cavitating pulmonary aspergillosis in a 28-year-old alcoholic patient with past history of tuberculosis now presenting with low grade fever and cough for more than 2 months. The bronchial washings showed Aspergillus and the serum immunoglobulin IgG antibodies to Aspergillus fumigate was positive. CT chest shows consolidation with breakdown and cavity formation in bilateral upper lobes. Few calcific foci are also noted within; (c) HRCT thorax of a 52-year-old diabetic female showing left upper lobe cavitating consolidation with a fungal ball. She fulfilled the criteria for CPA and was diagnosed with chronic necrotizing pulmonary aspergillosis; (d) HRCT thorax of a 43-year-old diabetic male showing bilateral cavitation, fibrosis and traction bronchiectasis suggestive of chronic fibrosing pulmonary aspergillosis.

[Table/Fig-7]:

CT thorax of a 40-year-old asthmatic female: (a) Sagittal; and (b) axial images show central varicose bronchiectasis (arrows). ABPA was diagnosed through the Greenberger-Patterson criteria and she had achieved remission after steroid therapy was initiated; (c) CT thorax of the same patient done 2 years later when she returned with recurring symptoms shows dilated, mucus-filled dilated bronchi (gloved finger appearance; represented by arerows).

[Table/Fig-8]:

Chest Radiograph Posteroanterior view of another patient with ABPA (allergic bronchopulmonary aspergillosis) shows V shaped tubular opacities in the right parahilar location (arrowheads).

[Table/Fig-9]:

Fungal ball: Cavitary tuberculosis with fungal ball (aspergilloma): 32-year-old male patient presented with cough and chest pain (a) Coronal HRCT scan (b) Magnified view of the lesion (c) Prone scan reveals an area of consolidation with cavitations involving left apical region with a well defined nodular opacity with air crescent within the cavity. Prone scan shows the nodular opacity is mobile and settled in the dependent position.

[Table/Fig-10]:

HRCT thorax of a 24-year-old farmer with chronic hypersensitivity pneumonitis due to A. fumigatus. (a) coronal section showing upper lobe predominance of the disease in the form of (b) parenchymal fibrosis, interlobular and intralobular interstitial thickening and centrilobular nodules.