Definition

Idiopathic pulmonary fibrosis is classified by the American Thoracic Society (ATS) and European Respiratory Society (ERS) as an idiopathic interstitial pneumonia (chronic form of idiopathic interstitial pneumonia).

Epidemiology

Most common form of idiopathic interstitial pneumonia, accounting for about 50% of cases Occurs at age 40–50 years More common in men than in women.

Etiology, pathophysiology, pathogenesis

Inflammatory fibrotic disorder of the pulmonary parenchyma of uncertain etiology Areas of fibrotic changes in various stages alternating with normal parenchyma Nodular fibrosis and honeycomb cystic destruction.

Imaging Signs

Modality of choice

CT.

Radiographic findings

Reticular shadowing, primarily in the basal segments.

CT findings

Reticular shadowing Honeycombing Traction bronchiectasis Focal ground-glass opacities Disorganization of pulmonary architecture Predilection for the peripheral, basal, and subpleural regions Apicobasal gradient.

Pathognomonic findings

CT findings in the context of corresponding clinical data are diagnostic (sensitivity is about 50%, specificity > 90%, positive predictive value > 90%); biopsy is not required.

Clinical Aspects

Typical presentation

Initially insidious but progressive respiratory distress over > 6 months Nonproductive cough Clubbed fingers (occurs in up to 50% of cases).

Therapeutic options

Responds to steroids only in combination with ciclosporin Lung transplant.

Course and prognosis

Prognosis is not favorable Median survival time after diagnosis is 2.5–3.5 years.

What does the clinician want to know?

Confirmation of the diagnosis Course Complications (other opportunistic infections, Pneumocystis jirovecii pneumonia).

Fig. 5.1 Idiopathic pulmonary fibrosis.

a The plain chest radiograph shows extensive, primarily reticular and honeycomb interstitial changes.

b CT shows primarily basal and peripheral subpleural interstitial honeycombing. The trabeculation of the pleural boundaries (arrow), bronchiectasis resembling a string of pearls (open arrow), bronchiectasis resembling a string of pearls (open arrow), ectasia of the trachea and main bronchi (*) are further signs.

Tips and Pitfalls

Radiographic findings are often suggestive and permit a diagnosis in about 70% of cases.

Selected References

American Thoracic Society/European Respiratory Society. International multidisciplinary consensus classification of the idiopathic interstitial pneumonias. Am J Respir Crit Care Med 2002; 165: 277–304

Kim DS, Collard HR, King TE. Classification and natural history of the idiopathic interstitial pneumonias. Proc Am Thor Soc 2006; 3: 285–292

Müller-Lang C et al. [Idiopathische interstitielle Pneumonien.] Radiologe 2007; 47: 384–392 [In German]

Wittram C, Mark EJ, McLoud TC. CT–histologic correlation of the ATS/ERS 2002 classification of idiopathic interstitial pneumonias. Radiographics 2003; 23: 1057–1071

Definition

Cryptogenic organizing pneumonia is classified by the ATS and ERS as an idiopathic interstitial pneumonia (subacute form of idiopathic interstitial pneumonia) Formerly referred to as bronchiolitis obliterans.

Epidemiology

Idiopathic cryptogenic organizing pneumonia is a rare form of idiopathic interstitial pneumonia, accounting for about 10% of cases Occurs at age 40–50 years No sex predilection More common in smokers than in nonsmokers.

Etiology, pathophysiology, pathogenesis

Rare in its idiopathic form; more common secondary to collagen diseases and infectious or drug-induced pulmonary disorders Polypoid granulomatous inflammation of the respiratory bronchioles and alveoli without disorganization of the pulmonary architecture.

Imaging Signs

Modality of choice

CT.

Radiographic findings

Unilateral or bilateral nodular opacities Resembles pneumonia.

CT

Bilateral focal non-segmental consolidations in the subpleural or peribronchial regions (> 80% of cases) Tendency to migrate An air bronchogram is common Perifocal ground-glass opacity (in 60% of cases) Peribronchiolar centrilobular round focal lesions < 10 mm with irregular borders in up to 50% of cases.

Pathognomonic findings

Focal areas of consolidation with air bronchogram and associated ground-glass opacification in the subpleural or peribronchial region Findings are unchanged or progressive for weeks despite antibiotics.

Clinical Aspects

Typical presentation

Subacute onset over a period of up to 3 months Nonproductive cough Subfebrile temperatures Often a lower airway infection is initially suspected Restrictive pulmonary dysfunction.

Confirmation of the diagnosis

Biopsy.

Therapeutic options

Inhalational or systemic steroids.

Course and prognosis

Prognosis is good with steroid therapy.

What does the clinician want to know?

Diagnosis Course under therapy.

Fig. 5.2 Cryptogenic organizing pneumonia in a 67-year-old woman.

a The plain chest radiograph shows isolated moderately sharply demarcated focal densities bilaterally but primarily on the right side. The right hilar bronchovascular bundles appear slightly thickened.

b CT shows the focal lesions as homogeneous areas of consolidation with isolated excursions but otherwise without any reaction in the adjacent tissue.

Tips and Pitfalls

Can be misinterpreted as pneumonia.

Selected References

American Thoracic Society/European Respiratory Society. International multidisciplinary consensus classification of the idiopathic interstitial pneumonias. Am J Respir Crit Care Med 2002; 165: 277–304