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Azygos arch valves: prevalence and appearance at contrast-enhanced CT

Benjamin M Yeh1, Fergus V Coakley, Henry C Sanchez

  • 1Departments of Radiology and Pathology, University of California San Francisco, 505 Parnassus Ave, Box 0628, M 372, San Francisco, CA 94143-0628, USA. benyeh@itsa.ucsf.edu

Radiology
|December 3, 2003
PubMed

Insights

Azygos arch valves are common, appearing in over 68% of contrast-enhanced CT scans. High injection rates and right arm contrast injections increase the likelihood of visualizing these azygos valves.

Area of Science:

  • Radiology
  • Anatomy
  • Medical Imaging

Background:

  • The azygos arch is a venous structure in the thorax.
  • Azygos valves are leaflets within the azygos arch, similar to venous valves elsewhere.
  • Their prevalence and appearance on imaging are not well-established.

Purpose of the Study:

  • To determine the frequency of azygos arch valves.
  • To describe the imaging appearance of azygos valves using computed tomography (CT).
  • To investigate factors influencing the visualization of azygos valves during contrast-enhanced CT.

Main Methods:

  • Retrospective review of 309 contrast-enhanced spiral CT chest examinations.
  • Assessment for contrast material reflux into the azygos arch and focal bulges.
  • Definition of an azygos valve based on contrast material contour within the arch.
  • Statistical comparison of reflux rates based on injection rate and arm used.

Main Results:

  • Azygos valves were visualized in 105 (68.2%) of 309 examinations.
  • Contrast reflux into the azygos arch occurred in 49.8% of scans.
  • Valves were more frequently seen with high injection rates (64.8%) and right arm injections (76% in high-rate group).
  • Refluxed contrast appeared as discrete collections within valve cusps in 44.8% of positive reflux cases.

Conclusions:

  • Azygos arch valves are a common finding on contrast-enhanced CT.
  • Higher contrast injection rates and right arm injections enhance the detection of azygos valves.
  • These findings have implications for interpreting thoracic venous anatomy on CT.
Abstract

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