Obstructive Pulmonary Diseases of the Lower Airways…It’s not all

Emphysema!

Karin and Jason Kuhl

4/14/04

What’s your differential diagnosis?

52 yo male with chronic cough, dyspnea, and occasional wheezing

100 pack year smoking history

PFT’s demonstrate an obstructive pattern

Obstructive Pulmonary Diseases

Any disease affecting the upper or lower airways can be associated with obstruction of airflow from the lungs.

This presentation will focus on those pathological processes primarily affecting the lower airways, including:– Emphysema– Chronic Bronchitis– Asthma– Bronchiectasis– Bronchiolitis obliterans (constrictive bronchiolitis)

COPD

Chronic obstructive pulmonary disease (COPD) is a general term lumping emphysema, chronic bronchitis, and asthma together.

COPD is not used to describe the other disease states resulting from chronic airflow obstruction.

Disadvantages of using the term COPD:– Other obstructive conditions are often over-looked.– Pathologic and physiologic mechanisms of these

diseases are different.– Prognosis and treatment are disease specific.

Emphysema

Defined by the American Thoracic Society as “the permanent enlargement of the air spaces distal to the terminal bronchiole as a result of destruction of the alveolar walls without significant fibrosis.”

Three principle types: Centriacinar (centrilobular)

– Predominantly in upper lung zones.– Associated with smoking & pneumoconiosis.

Panacinar (panlobular)– More progressive, and with more severe symptoms

because it involves the lower lung zones (areas of greater gas exchange).

– Associated with alpha-1-antitrypsin deficiency. Distal acinar (paraseptal)

– Focal or multifocal disease.– Involves distal alveolar sacs and ducts, resulting in

subpleural blebs and bullae.– More likely to cause spontaneous pneumothorax.

Pathology of the secondary pulmonary lobule:

A. Normal B. Centriacinar C. PanacinarD. Paraseptal

Webb1

Protease-Anti-protease Theory:

Emphysema results from the destructive effect of high protease activity in subjects with low anti-protease activity.

Cotran2

Normal lung and emphysema:

Marc Gosselin, MD

Airflow obstruction is due to the loss of elastic recoil of the lung parenchyma.

Lynch3

Clinical manifestation:

Insidious onset Dyspnea Noncyanotic (pink

puffer) Mild cough +/- Increased sputum +/- Wheezing AP diameter Usually thin

Chest radiographic findings:

Poor in evaluating very early disease due to limitations in small airway visualization.

As the disease progresses, radiograph can directly demonstrate disease pathology, as well as indirect signs of increased lung compliance and air-trapping.

Identification of emphysema on CXR:

Direct identification:– Irregular, asymmetric

areas of decreased lung density.

– Vascular deficiency: Rapidly attenuating

peripheral pulmonary arteries, may be absent peripherally

Increased branching angles

Smaller-than-expected caliber

– Bullae– Saber-sheath trachea

Indirect identification:– Signs of

hyperinflation: Flattened

diaphragm Sterno-

diaphragmatic angle >90o on lateral

Increased width of retrosternal air space

Increased AP diameter

Increased intercostal distance

Emphysema

Giant Bullous Emphysema (“Vanshing Lung” Syndrome)

Giant bulla with missing vascular shadows.

Emphysema: Trachea

Saber-sheath trachea.

www.radiology.vcu.edu

CT findings: Relatively well-defined, low attenuation areas

with very thin (invisible) walls, surrounded by normal lung parenchyma.

As disease progresses:– Amount of intervening normal lung decreases. – Number and size of the pulmonary vessels decrease.– +/- Abnormal vessel branching angles (>90o), with

vessel bowing around the bullae.

Centrilobular Emphysema

Emphysematous Bullae

www.ctsnet.org/doc/6761

Chronic Bronchitis

Presence of a chronic, productive cough for 3 or more months, in at least 2 consecutive years, when all other causes of cough have been excluded (clinical diagnosis).

Pathology:

Hypertrophy of the submucusal glands in the trachea and bronchi, and an increase in goblet cells in the small bronchi and bronchioles, leads to excessive mucus production and obstruction.

Caused by tobacco smoke and other inhaled pollutants, not infection.– Infection appears to be significant in

maintaining the disease.

Cotran2

Airflow obstruction caused by:

Mucus plugging of large and small airway lumens.

Airway alterations:– Inflammatory

infiltration– Bronchiolar wall

fibrosis

Clinical manifestation:

Cough Copious sputum Cyanotic (blue

bloater) +/- dyspnea +/- rhonchi/wheezing Usually obese

Chest radiographic findings:

It is difficult to know which radiographic findings are attributable to chronic bronchitis, rather than to emphysema, because they commonly coexist.

Chest radiograph is often not reliable at detecting or excluding chronic bronchitis.– CXR is helpful in excluding diseases that can

clinically mimic chronic bronchitis (TB, tumor, bronchiectasis, abscess).

Principle Radiographic abnormalities:

Thickening of bronchial wallsOverinflation*Oligemia*Evidence of Pulmonary Arterial

Hypertension

*The overinflation and oligemia seen in chronic bronchitis may also be due to superimposed emphysema.

Chronic Bronchitis Normal Exacerbation

Arrows show parallel linear shadows indicating bronchial wall thickening.Webb, RW1

Chronic Bronchitis

Bronchogram shows dilation, narrowing, and abrupt termination (arrows) of various small bronchi.

Webb, RW1

CT findings:

Limited literature on CT features of chronic bronchitis.

Bronchial wall thickening has been documented in patients with chronic bronchitis, but has also been observed in patients without respiratory symptoms.

Chronic Bronchitis

CT?

Quantitative CT:

Spirometically triggered images at 10% and 90% vital capacity (VC) have been reported to be able to distinguish patients with chronic bronchitis from those with emphysema.– Patients with emphysema had significantly lower mean

lung attenuation at 90% VC than normal subjects or patients with chronic bronchitis.

– Attenuation was the same for normal subjects and those with chronic bronchitis.

Asthma

A chronic, relapsing inflammatory disorder characterized by hyperactive airways, leading to episodic, reversible bronchoconstriction.

Two Types:– Extrinsic: initiated by a type I hypersensitivity reaction,

induced by exposure to an extrinsic antigen.– Intrinsic: initiated by diverse, non-immune mechanisms

(stress, pulmonary infection, exercise, cold, etc.).

Pathology:

Large & small airway mucus plugging

Airway infiltrated with inflammatory cells

Tissue edema & epithelial disruption

Sub-basement membrane collagen deposition

Hypertrophy of smooth muscle

Hypertrophy of submucosal glands

Cotran2

Obstruction is caused by:

Bronchoconstriction

Airway wall edema and inflammatory thickening

Mucus plugging

Clinical Manifestation:

Cough (usually worse at night)

Dyspnea Wheezing Chest tightness Symptoms often worse

with:– Exercise – Allergens– Smoke– Changes in weather– And many others…

Chest radiographic findings:

Bronchial wall thickening: Most CommonAir-trapping (hyperinflation found in 25%)Atelectasis: From mucus plugging+/- bronchial constriction+/- bronchial dilatation

Asthma: Airway Thickening Most Common Finding

Asthma: Airway Thickening and Hyperinflation

Thin Section CT findings:

Bronchial wall thickeningMucoid impactionMosaic lung attenuation with air trapping

– Findings may be reversible with pharmacologic treatment.

Centrilobular thickening

Asthma: Airway Thickening and Lucent Areas of Decreased Ventilation (Mosaic Perfusion)

Bronchiectasis

A chronic, necrotizing infection of the bronchi & bronchioles, leading to abnormal, permanent dilatation of the involved airways.

May develop in association with:– Bronchial obstruction: localized (tumor, foreign body)

or diffuse (asthma, chronic bronchitis)– Congenital/Hereditary: CF, Kartagener’s syndrome– Necrotizing pneumonia

Incidence markedly decreased, due to the advent of antibiotics and immunizations.

Pathology:

Obstruction and infection are the major influences associated with bronchiectasis.

Bronchial obstruction leads to atelectasis of airways distal to the obstruction.

Bronchial wall inflammation & intraluminal secretions cause dilatation of the patent airways proximal to the obstruction.

Pathology:

Process becomes irreversible if the obstruction persists or if there is added infection.

Vicious cycle of recurrent/chronic infections perpetuates the airway inflammation & dilatation, leading to extensive endobronchial destruction.

FYI: There are different types of bronchiectasis:

Cylindrical– Airway wall is regularly/uniformly dilated.

Varicose– Greater dilatation with alternating areas of constriction

and dilatation. Cystic

– Progressive, distal enlargement resulting in sac-like terminations of the airways.

– Cystic spaces can be several centimeters in diameter and contain air-fluid levels.Most severe

Clinical Manifestations:

Chronic cough and expectoration of copious, purulent sputum.

+/- dyspnea +/- hemoptysis +/- fever, weight loss,

anemia, clubbing

Chest radiographic findings:

Earliest finding is bronchial wall thickeningWith further dilatation & wall thickening,

see “tram lines” & “ring shadows” (Curved reticular opacities).

There is often initially some generalized overinflation of involved lobe (from concurrent small airways involvement).

In advanced stages, areas of atelectasis and collapse develop.

Bronchiectasis: Pathology and Bronchogram -

Historical Imaging Method of Diagnosis

Bronchiectasis: Cystic Fibrosis

Most frequent CT findings:

Lack of tapering of the bronchial lumen

Bronchial wall thickeningBronchial dilatationVisualized peripheral bronchiMucus plugging

Most frequent

Less frequent

Bronchiectasis

Radiology 2002; 225: 663-672

Arrows demonstrating various grades of bronchial wall thickening,with concurrent mucus plugging (arrowheads) in some bronchial lumens.

Cystic Bronchiectasis

www.emedicine.com

Bronchiectasis

Radiology 1999; 212: 67-68

“Signet ring” sign

Signet ring?

“Question Dogma” …Marc Gosselin, MD

or

Solitaire ring?

Bronchiolitis Obliterans

Pathologic fibrosis (scarring) of the small airways, leading to luminal narrowing and irreversible airflow obstruction.

Virtually any inflammatory process that leads to scarring can cause BO.

Bronchiolitis Obliterans

May be seen as the result of:– Childhood viral infection (Swyer-James Syndrome)– Mycoplasma pneumonia– Toxic fume inhalation

Common pulmonary problem in patients with:– Rheumatoid arthritis (especially if taking

penicillamine)– Chronic GVH following BMT– Chronic rejection after heart-lung or lung transplant

Pathology:

Submucosal and peribronchiolar inflammation and fibrosis cause concentric narrowing of the bronchiolar lumen and mucus stasis.

Complete obstruction of the airway occurs by either fibrosis squeezing the lumen shut, or intraluminal plug formation.

Alveolar ventilation beyond the obstruction continues via the terminal conducting airways, adding to the degree of air trapping.

Clinical manifestation:

Cough Dyspnea Fatigue Diagnosis of BO:

– Irreversible airflow obstruction with a FEV1 <60% of predicted in the absence of emphysema, chronic bronchitis, asthma, or other causes of airway obstruction.

Chest radiographic findings:

Chest radiograph often subtle findings.May be able to discern hyperinflation due

to:– Air trapping– Vessel attenuation– Bronchial wall thickening

Involvement of one lung usually represents Swyer-James Syndrome.

Classic Bronchiolitis Obliterans (History and CT), But given a diagnosis of emphysema. (We

diagnosis what we know, so know a lot!)

CT findings:

Mosaic attenuationBronchial dilatationAir trapping

– Expiratory HRCT facilitates detection of areas of decreased attenuation.

Bronchiolitis Obliterans

Radiology 2000; 216: 472-477

• Single arrows: air trapping• Double arrows: subtle areas of relatively increased lung attenuation represent

normal, collapsing lung

Inspiratory & expiratory views of bronchiolitis obliterans

Marc Gosselin, MD

Obstructive Pulmonary Diseases of the Lower Airways

Imaging can be helpful in diagnosing lower airway obstructive disease; however, there is much overlap in findings.

It is necessary to integrate the clinical presentation, abnormal physiology, and imaging findings to correctly diagnose the disorder.

Consider ALL obstructive pathology when first establishing your differential diagnosis.

Remember, it’s NOT all emphysema…

References:

1. Webb, RW. The Radiologic Clinics of North America: Imaging of obstructive Pulmonary Disease. W.B. Saunders Company. Philadelphia, PA. Vol. 36(1). January, 1998.

2. Cotran RS, Kumar V, Collins T. Robbins Pathologic Basis of Disease: 6th ed. W.B. Saunders Company. Philadelphia, PA. 1999. pp: 711-717.

3. Lynch DA, Newell JD, Lee JS. Imaging of Diffuse Lung Disease. B.D. Decker Inc. Hamilton, Ontario. 2000. pp: 171-200.

4. Sharma V, Shaaban AM, Berges G, Gosselin M. The radiological spectrum of small-airway disease. Seminars in Ultrasound, CT, and MRI. 23(4): 339-351, 2002.

5. Webb RW, Muller NL, Naidich DP. High-Resolution CT of the Lung: 3rd ed. Lippincott Williams & Wilkins. Philadelphia, PA. 2001. pp: 467-546.