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CHEST IMAGE
Year : 2017  |  Volume : 5  |  Issue : 1  |  Page : 60-61

Saber-sheath trachea


1 Department of Pulmonary Medicine, Medical College, Kolkata, India
2 Department of Pulmonary Medicine, Murshidabad Medical College, Murshidabad, West Bengal, India

Date of Web Publication29-Dec-2016

Correspondence Address:
Sibes K Das
Department of Pulmonary Medicine, Medical College, Kolkata
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2320-8775.196661

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How to cite this article:
Das SK, Das A, Sarkar S, Samanta H. Saber-sheath trachea. J Assoc Chest Physicians 2017;5:60-1

How to cite this URL:
Das SK, Das A, Sarkar S, Samanta H. Saber-sheath trachea. J Assoc Chest Physicians [serial online] 2017 [cited 2017 May 23];5:60-1. Available from: http://www.jacpjournal.org/text.asp?2017/5/1/60/196661

A 55-year-old man, a known case of chronic obstructive pulmonary disease (COPD), was admitted with nonsevere exacerbation. He was treated with controlled oxygen, intravenous coamoxyclav, nebulization with salbutamol, and oral prednisolone. His chest radiograph showed evidence of hyperinflation along with intrathoracic narrowing of trachea [Figure 1]. High-resolution computed tomography (HRCT) scan of thorax showed presence of multiple bullae, evidence of emphysema, and reduction of coronal diameter and increase of sagittal diameter of intrathoracic trachea suggestive of saber-sheath trachea [Figure 2].
Figure 1: Chest X-ray PA view showing narrowing of intrathoracic trachea along with evidence of hyperinflation

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Figure 2: HRCT scan of thorax showing saber-sheath trachea along with multiple bullae and emphysema

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Saber-sheath trachea is a fixed deformity of the intrathoracic trachea, which is characterized by reduction in coronal diameter associated with an increase in sagittal diameter, as conventionally measured 1 cm above the aortic arch. The extrathoracic trachea is normal. It is considered to be present when tracheal index, i.e., ratio of coronal to sagittal diameter is <0.50.[1] It is considered as diagnostic of COPD.[2] The sensitivity of this sign is above 90% but the specificity is below 40%.[3] It is thought to be because of increased intrathoracic pressure as a result of hyperinflation, chronic injury, and softening of tracheal cartilage secondary to chronic cough. Saber-sheath trachea is generally evident after the age of 50 years. It is unlikely to contribute significantly to airflow obstruction. Saber-sheath trachea may provide a clue to the presence of COPD when other radiological signs are absent.[4] In computed tomography (CT), there is inward displacement of the lateral portions of the tracheal wall and tracheal cartilage with side-to-side narrowing of the tracheal lumen. The tracheal wall usually is of normal thickness. During forced expiration, CT demonstrates further inward bowing of the tracheal walls in many patients.[5]

Saber-sheath trachea is correlated with functional severity, being more common in global initiative for chronic obstructive lung disease (GOLD) stages III and IV.[6] Chest radiography is considered as good as CT scan in detecting this deformity. Saber-sheath trachea is considered a fixed tracheal deformity, as the tracheal index does not change over time.

As chest radiograph is routinely performed in the evaluation of patients with COPD, we recommend performing a careful assessment of intrathoracic trachea, which can provide the physician with important clues to the presence of COPD, specially in the presence of otherwise negative or nonspecific radiological findings.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Marom EM, Goodman PC, McAdam HP. Diffuse abnormalities of the trachea and main bronchi. AJR Am J Roentgenol 2001;176:713-7.  Back to cited text no. 1
    
2.
Green R. “Saber-sheath” trachea: Relation to chronic obstructive pulmonary disease. AJR Am J Roentgenol 1978;130:441-5.  Back to cited text no. 2
    
3.
Tsao TC, Shieh WB. Intrathoracic tracheal dimensions and shape changes in chronic obstructive pulmonary disease. J Formos Med Assoc 1994;93:30-4.  Back to cited text no. 3
    
4.
Fraser RS, Muller NL, Colman N, Pare PD, editors. Fraser and Pare’s diagnosis of the diseases of the chest. 4th ed, vol III. Philadelphia: WB Saunders; 1999. pp. 2168-263.  Back to cited text no. 4
    
5.
Webb EM, Elicker BM, Webb WR. Using CT to diagnose nonneoplastic tracheal abnormalities: Appearance of the tracheal wall. AJR Am J Roentgenol 2000;174:1315-21.  Back to cited text no. 5
    
6.
Ciccarese F, Poerio A, Stagni S, Attinà D, Fasano L, Carbonara P et al. Saber-sheath trachea as a marker of severe airflow obstruction in chronic obstructive pulmonary disease. Radiol Med 2014;119:90-6.  Back to cited text no. 6
    


    Figures

  [Figure 1], [Figure 2]



 

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