Radiology/Pathology Correlation

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The patient is a 31-year-old man, previously healthy, who was involved in a house fire approximately 1 year prior to his high-resolution chest CT scan. During the intervening year, the patient had been experiencing progressively worsening shortness of breath. Pulmonary function testing showed an obstructive defect.

Radiology

HRCT

Figure 1

This inspiratory image through the upper lungs is essentially normal. There is no evidence of ground-glass opacity, nodules, or mosaic perfusion.

Figure 2

This static postexpiratory scan, obtained at residual volume after the patient has performed a forced vital capacity maneuver (meaning the scan is performed after the patient is given these breathing instructions: "take a deep breath in, blow it all out, stop breathing") is also normal.

Figure 3. This dynamic expiratory image through the upper lungs is acquired by scanning continuously at the same location while the patient performs a forced vital capacity maneuver (meaning the scan is acquired during active exhalation after the patient is told to take a deep breath in and blow it out fast).

normalabnormal1abnormal2

Describe the abnormality. Answer

Outline an area of normal left lung. Click on the structure in the image to get verification.

Outline two areas of abnormal left lung.

What is the differential diagnosis?

Answer

Note: At UCSF, we perform dynamic expiratory imaging using a decreased radiation dose, which is why this image is somewhat "grainier" or "noisier" than normal. Because the lung has inherently high contrast (air surrounding soft tissue, such as a nodule or normal lung collapsing during exhalation), the increased image noise does not compromise diagnostic ability. Dynamic (rather than static) expiratory imaging is more sensitive for the detection of subtle or transient, but physiologically significant, air trapping.


Pathology

The following images are from a 49-year-old man with a similar history. This centrilobular, bronchiolovascular bundle shows two bronchioles and the accompanying pulmonary artery. The interstitium is thickened around the airways and the vessel, and there is a mild chronic inflammatory infiltrate. Epithelium is intact but the lumen of the smaller airway has a mucous plug.

bronchiole1bronchiole2pulma

Figure 4

Find the two bronchioles with irregularly-shaped lumens.

Find the pulmonary artery with a thickened media.

To see a normal bronchiole, click here.

Figure 5: This elastic van Gieson stain shows another bronchiolovascular bundle. The elastic tissue of the airway and the artery stains black, and collagen stains red. Note the eccentric subepithelial scar and chronic inflammation in the bronchiole. The smooth muscle of the airway and part of its elastic tissue have been destroyed. Collagenous scar surrounds the pulmonary artery.

pulmartsubepithscar

 

Find the eccentric subepithelial inflamed scar around the airway.

Find the pulmonary artery with surrounding scar.

Figure 6: The lumen of this airway is filled with connective tissue with little collagen. Again the artery is surrounded by collagenous scar. Note the intimal thickening that narrows the lumen of the artery.

artintairway

 

Find the airway.

Find the intimal thickening of the artery.

What is the diagnosis? Answer

Scroll down after answering the question.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bronchiolitis Obliterans (Syn: Constrictive Bronchiolitis)

Discussion: Bronchiolitis obliterans (BO), also known as obliterative bronchiolitis, is a nonspecific reaction involving the small airways, caused by a variety of injuries. The final common pathway of a variety of insults is concentric fibrosis in the bronchiolar and peribronchiolar tissues, which results in narrowing of these airways. It must be distinguished from bronchiolitis obliterans organizing pneumonia (BOOP, preferably called cryptogenic organizing pneumonia (COP)), which involves bronchioles and surrounding alveolar spaces.

Note: To return here after viewing, click here before clicking on the condition.

Certain conditions are associated with the development of BO, including:

  1. collagen vascular diseases (especially rheumatoid arthritis) [1]
  2. post pneumonia, including viral (adenovirus, cytomegalovirus, measles, and influenza), or bacterial (mycoplasma) types. This form of BO, when unilateral, is known as the Swyer-James syndrome [2]
  3. toxic fume inhalation (see above case), including also SO2, NO2, NH3, Cl2, phosgene, ozone, H2S, and fumes in a popcorn plant [3]
  4. chronic rejection in lung transplant patients [4]
  5. graft vs host reaction in bone marrow transplant recipients [5]
  6. certain drugs (particularly penicillamine, gold, and Sauropus androgynus)[6]
  7. neuroendocrine cell hyperplasia
  8. inflammatory bowel disease [7]
  9. ciliary dyskinesia
  10. panbronchiolitis
  11. idiopathic bronchiolitis obliterans [8]

Chest Radiography: Chest radiographs in patients with BO are often normal. Occasionally, when the etiology of BO is Swyer-James syndrome, the affected side may show a small hilum with diminished lung volume at full inspiration. On expiratory imaging, the air trapping that characterizes BO due to Swyer-James syndrome results in shift of the mediastinum away from the affected side. Because other etiologies of BO usually result in bilateral disease, chest radiography often is normal or shows only mildly increased lung volumes. Airway dilation may be seen in severe cases.

HRCT: HRCT scans show geographic areas of decreased lung attenuation with abnormally small vessels on inspiratory images (called mosaic perfusion), with air trapping on expiratory scans. Occasionally, in severe cases, bronchial dilation may be evident on inspiratory studies. In some patients, the inspiratory scan may appear normal, and the only abnormal finding is air trapping on expiratory scans. In this case, BO is the most common diagnosis, although hypersensitivity pneumonitis, chronic bronchitis, and asthma may also cause this phenomenon. Idiopathic BO and BO associated with the above conditions have the same HRCT appearance. For further information on mosaic perfusion, click here. (Use the "back" button in the menu bar to return.)

Pathologic changes: The diseases illustrated here, with the exception of diffuse panbronchiolitis, involve predominantly the bronchioles without affecting the surrounding alveoli. Thus, the airways themselves (< 2 mm in diameter) are not visible on HRCT, and mosaic perfusion is the radiographic hallmark of disease. Nodules and branching opacities (tree-in-bud pattern) represent other patterns of bronchiolar inflammation that expand the peribronchiolar inflammation (panbronchiolitis, for example).

Histologically, epithelial erosions are common, and goblet cells maybe hyperplastic. Luminal exudate and mucus may be present. Subepithelial granulation tissue and scar replace wall structures variably and encroach on the lumen. Sometimes, however, mural smooth muscle is hyperplastic. An elastic van Gieson stain is useful to show the increased connective tissue between the epithelium and the elastic layer that hugs the smooth muscle (also see Figure 5 above) [9].

Inflammatory cells may be either acute or chronic. Chronic inflammatory infiltrates designated cellular or lymphocytic bronchiolitis or follicular bronchiolitis are potentially reversible, but when fibrosis develops, the term constrictive bronchiolitis (BO) is used.

Varied changes in the accompanying small pulmonary arteries (intimal, medial, and/or adventitial thickening) may account for the decreased vascularity of hypoventilated lung [9]. Finally, the disease is patchy (see the HRCT), and biopsies must be examined carefully to find lesions.

When the initial injury persists or when secondary infection occurs, inflammation may spread proximally to give rise to bronchiectasis, as wall support structures are gradually replaced by granulation tissue and scar. This evolution of bronchiolitis to bronchiectasis, a common sequence, is the basis for the proposed term "bronchiolitis-bronchiectasis complex" or BBC.

Summary of Radiographic Changes in Bronchiolitis Obliterans

Summary of Pathologic Changes

Diagnosis: Bronchiolitis obliterans (syn: constrictive bronchiolitis) due to toxic fume inhalation.

References: To return to reference section after viewing abstract, click here before clicking on "abstract".

1. Remy-Jardin M, Remy J, Cortet B, Mauri F, Delcambre B. Lung changes in rheumatoid arthritis: CT findings. Radiology 1994; 193:375-282. Abstract

2. Chang A, Masel J, Masters B. Post-infectious bronchiolitis obliterans: clinical, radiological and pulmonary function sequelae. Pediatr Radiol 1998; 28:23-29. Abstract

3. Kreiss K, Gomaa A, Kullman G, Fedan K, Simoes E, Enright P. Clinical bronchiolitis obliterans in workers at a microwave-popcorn plant. N Engl J Med 2002; 347:330-338. Abstract

4. Nathan S, Ross D, Belman M, Shain S, Elashoff J, Kass R, Koerner S. Bronchiolitis obliterans in single-lung transplant recipients. Chest 1995; 107:967-972. Abstract

5. Worthy S, Flint J, Müller N. Pulmonary complications after bone marrow transplantation: high-resolution CT and pathologic findings. Radiographics 1997; 17:1359-1371. Abstract

6. Yang C, Wu M, Chiang A, Lai R, Chen C, Tiao W, McLoud T, et al. Correlation of high-resolution CT and pulmonary function in bronchiolitis obliterans: a study based on 24 patients associated with consumption of Sauropus androgynus. AJR 1997: 168:1045-1050. Abstract

7. Vandenplas O, Casel S, Delos M, Trigaux J-P, Melange M, Marchand E. Granulomatous bronchiolitis associated with Crohn's disease. Am J Resir Crit Care Med 1998; 158:1676-1679. Abstract

8. Sweatman M, Millar A, Strickland B, Turner-Warwick M. Computed tomography in adult obliterative bronchiolitis. Clin Radiol 1990; 41:116-119. Abstract

9. Colby T. Bronchiolitis. Pathologic considerations. Am J Clin Pathol 1998; 109:101-109. Abstract

TOP----Rad/Path Home Page

Last modified 11/11/02

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This image shows bilateral inhomogeneous lung opacity. The "whiter" areas, representing normal collapsing lung, are expected with postexpiratory scanning. The "blacker" areas represent air trapping. Extensive air trapping was seen throughout the mid and lower lungs as well.

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Differential diagnosis: The presence of significant air trapping on HRCT scans indicates the presence of an airway disorder, either a large airway disease, such as bronchiectasis, or a small airway disorder. The latter includes the numerous causes of bronchiolitis. In this case, some causes of bronchiolitis, such as respiratory bronchiolitis, panbronchiolitis, and bronchiolitis obliterans organizing pneumonia, may be excluded due to the lack of other abnormalities on the scan (such as nodules, bronchiectasis, and consolidation). Additional causes of bronchiolitis, such as hypersensitivity pneumonitis, bronchiolitis obliterans, and chronic bronchitis, still deserve consideration. Asthma is also a possibility.

The absence of a smoking history excludes chronic bronchitis, and the obstructive defect observed on pulmonary function testing was not reversible with bronchodilators, arguing against asthma. Furthermore, the patient had no exposure history to suggest hypersensitivity pneumonitis. The history of the house fire preceding the progressive respiratory decline in a previously healthy young adult is suggestive of bronchiolitis obliterans.

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Area of normal lung

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Area of abnormal lung

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Subepithelial scar with residual elastic tissue to the right but none elsewhere.

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Pulmonary artery

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Airway occluded by fibrous tissue

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Thickened intima of pulmonary artery

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Bronchiole

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Pulmonary artery with a thickened media

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Bronchiolitis obliterans (syn: constrictive bronchiolitis)

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