High-resolution CT of complications of idiopathic fibrotic lung disease

Abstract

Idiopathic pulmonary fibrosis (IPF) has a more variable clinical course than has been traditionally recognised. Many patients will remain stable over time while others experience relatively rapid deterioration. The prognosis and clinical course of patients with other fibrosing lung diseases is also variable. A number of conditions may complicate the clinical course of the idiopathic fibrosing lung diseases, which results in morbidity and mortality, but also represents potentially treatable causes of worsening symptoms. Infection and malignancy have a long-recognised association with IPF while other conditions, particularly pulmonary hypertension and acute exacerbation of IPF, are being increasingly recognised in this patient population. Many of these patients have serial high-resolution CT (HRCT) examinations that may demonstrate one or more of these supervening conditions. In this article we review the more common conditions that may complicate the course of idiopathic fibrosing lung disease with an emphasis on the HRCT appearance, which the reporting radiologist should be aware of.

Figure 1

Images from a 60-year-old man with biopsy-proven usual interstitial pneumonia complicated by Pneumocystis jiroveci pneumonia (PCP). The patient was on immunosuppressive treatment (prednisolone and azathioprine). (a) Baseline high-resolution CT (HRCT) through the mid-zones. (b) 2 months later following a week-long history of breathlessness, HRCT shows subtle, patchy ground-glass opacification superimposed on the fibrotic lung disease. A sputum sample stained positive for PCP.

Figure 2

(a,b) Two cases of Mycobacterium tuberculosis infection in fibrotic lung disease. In both instances a biopsy of the peripheral focal areas of consolidation were taken as part of an investigation for suspected lung cancer. No malignant cells were identified in either biopsy sample; however, tissue examination showed typical caseating granulomatous changes associated with pulmonary tuberculosis. Anti-tuberculosis therapy led to radiological resolution in both cases.

Figure 3

Mycetoma in the left lower lobe within the fibrotic lung (histopathological type unknown) in a 45-year-old woman.

Figure 4

Chronic necrotising aspergillosis in a 60-year-old man with idiopathic pulmonary fibrosis. Within the fibrobullous lung there is consolidation and an intracavitary body (air crescent sign). Following an extended course of antibacterial therapy without improvement, a positive culture for Aspergillus fumigatus was obtained from bronchoalveolar lavage of the right upper lobe.

Figure 5

Two examples of peripheral primary adenocarcinoma in fibrotic lung disease. (a) Biopsy-proven adenocarcinoma in the right upper lobe of a patient with fibrotic non-specific interstitial pneumonia (and some admixed paraseptal emphysema). (b) Peripheral adenocarcinoma in the right lower lobe of a 62-year-old man with usual interstitial pneumonia.

Figure 6

Accelerated idiopathic pulmonary fibrosis in a 65-year-old man. (a) Base line high-resolution CT (HRCT) shows coarse subpleural reticulation with peripheral traction bronchiectasis and microcystic honeycombing. (b) HRCT 3 months later after a 2 week history of progressive breathlessness shows patchy ground-glass change superimposed on the reticular abnormality, and within the previously relatively normal lung parenchyma. Despite aggressive immunosuppressive therapy, the disease progressed inexorably and the patient died 3 weeks later.

Figure 7

Pulmonary arterial hypertension (PAH) in fibrotic lung disease. (a) In the setting of pulmonary fibrosis the absolute dimensions of the main pulmonary artery are not necessarily a reliable indicator of PAH. However, a main pulmonary artery (solid arrow) to ascending aorta (broken arrow) ratio of greater than one is a reliable CT sign of PAH, as in this case. (b) A segmental pulmonary artery (white arrow) diameter to segmental bronchus (arrowhead) diameter ratio greater than one also indicates raised pulmonary arterial pressure.

Figure 8

CT of spontaneous pneumothorax in a 55-year-old man with biopsy-proven usual interstitial pneumonia who presented with severe acute breathlessness.

Figure 9

Pneumomediastinum in a man with advanced usual interstitial pneumonia.

Figure 10

(a) Dendriform ossification in a 62-year-old man with fibrotic lung disease of unknown cause. There are numerous small punctate and branching dense opacities, mainly in fibrotic lung. (b) Oblique 5 mm maximum-intensity projection demonstrates the branching nature of the heterotopic bone formation within areas of fibrosis.