Bronchiectasis in Cystic Fibrosis

Jeanne S Chow, MD
Bradley Snyder, MD
Andetta Hunsaker, MD

February 12, 1997

Presentation

Imaging Findings

Computed tomographs (CT) and plain radiographs of the chest demonstrate thickened bronchial walls. In addition, CT images show tubular dilated central bronchi (without tapering) (arrows) and mosaic oligemia (arrows), in which pulmonary segments most affected by bronchiectasis are distinguished from apparently normal lung tissue. Radiographs further demonstrate parallel line shadows (tram-lines) (arrows), ring shadows, and hyperexpansion (note flattened hemidiaphragms).

Differential Diagnosis

Etiologies include:

• cystic fibrosis
• bronchial wall weakness (eg, Williams-Campbell syndrome)
• prior infection (eg, childhood pneumonia, measles, pertussis, mycoplasma, and tuberculosis)
• obstruction (eg, neoplasms, broncholith, foreign body, bronchostenosis or atresia, granulomatous disease)
• inhalation and aspiration (eg, ammonia, Riley-Day syndrome, gastric aspiration, heroin overdose)
• impaired host defense (eg, allergic bronchopulmonary aspergillosis, Kartagener’s syndrome, primary impaired humoral or cell immunity, human immunodeficiency virus, lung transplant, inflammatory bowel disease)
• inflammation (eg bronchiolitis fibrosa obliterans)

Diagnosis

Discussion

CT, especially high resolution CT, is the best imaging modality for the evaluation of diseases of the bronchi and bronchioles. If a bronchus is larger than its accompanying pulmonary artery, it is thickened. On transverse view, this resembles a signet ring. Sagittal images of cylindrical bronchiectasis show parallel, thickened bronchial walls which resemble train or tram tracks; the varicose or saccular forms resemble a string of pearls. In bronchiectasis, bronchi do not taper normally. Distinct bronchi visible in the distal two thirds of the lung are abnormal. Bronchiectatic cysts, unlike blebs or bullae, have definable walls.

In this patient, bronchiectasis is due to cystic fibrosis (CF). Cystic fibrosis is a congenital disorder of the exocrine glands (including both mucus-secreting and eccrine sweat glands), which leads to mucinous obstruction in the lungs, pancreas, and liver. This disease is autosomal recessive and appears most commonly among Caucasians. A mutant gene of chromosome 7 encodes abnormal transport of chloride across epithelial membranes. In the lungs, failure to transport chloride into the airway lumen also decreases transport of sodium and water, leading to excessively viscous secretions.

Over 80% of those afflicted with cystic fibrosis have lung involvement. Respiratory failure is the most common cause of death. Mucoid impaction causes obstruction and secondary infection, especially by Staphylococcus aureus and Pseudomonas aeruginosa. Resultant fibrosis and cyst formation lead to bronchiectasis with a predilection for the upper lobes. Other complications include atelectasis, bronchitis, emphysema, bronchoceles, pneumothorax and hilar lymphadenopathy. Eventual obliteration of the vascular bed and chronic hypoxia lead to pulmonary arterial hypertension.

This patient’s respiratory failure eventually led to double lung transplantation.

References

2. Freundlich IM, Bragg DG. A radiologic approach to disease of the chest. Baltimore: Williams and Wilkins, 1992.

3. Hartman TE, Primack SL, Lee KS, Swenson SJ, Muller NL. CT of bronchial and bronchiolar diseases. Radiographics 1994; 14: 991-1003.

4. Kuhlman JE, Reyes BL, Hruban RH, Askin FB, Zerhouni EA, Fishman EK, Siegelman SS. Abnormal air-filled spaces in the lung. Radiographics 1993; 13(1): 47-75 (specific: 56-59).

5. Naidich DP, Zerhouni A, Siegelman SS. Computed tomography and magnetic resonance of the thorax. New York: Raven, 1991.

6. Reid LM. Reduction of bronchial subdivisions in bronchiectasis. Thorax 1950; 5:233-247.

7. Robbins SL, Cotran RS, Kumar V. Pathologic basis of disease. Philadelphia: Saunders, 1991.

8. Taccone A, Romano L, Marzoli A, Girosi D, Dell’Acqua A, Romano C. High resolution CT in cystic fibrosis. European Journal of Radiology 1992; 15: 125-129.

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