title: Azygos arch valves at computed tomography angiography and pitfalls related to its variety in appearance and function.
abstract: OBJECTIVE
  To evaluate the prevalence of azygos arch valves and assess azygos valve insufficiency at computed tomography angiography (CTA) of the chest or body with high rate contrast material injection.
  
  
  METHODS
  Three hundred twenty-one CTAs using high intravenous injection rates (3-5 mL/second) of 300 mgI/mL contrast material were retrospectively evaluated for the presence of contrast material reflux from the superior vena cava into the azygos vein. Among the patients with contrast material reflux, azygos valves were identified within the azygos arch. Age, sex, and site of contrast material injection were analyzed. Azygos valve insufficiency was considered to be present if there was contrast material within the azygos vein posterior to the azygos valve.
  
  
  RESULTS
  Of the 321 examinations, 191 (59.5%) showed reflux into the azygos vein. There was no significant difference in frequency of reflux into the azygos vein between right and left arm injection site (56.4% vs 63.5%, P = 0.20) or male and female patients (63.4% vs 55.0%, P = 0.12). No difference in mean age was noted between patients with reflux and those without it (P = 0.97). Azygos valves were identified in 124 (64.9%) of 191 CTA examinations with contrast reflux and pitfalls related to their appearance variety are discussed. No significant difference was found in valve frequency between male and female patients (66.0% vs 63.4%, P = 0.70). Contrast material posterior to the visible azygos valve was present in 66 (53.2%) of 124 examinations.
  
  
  CONCLUSIONS
  Azygos arch valves are a common finding on CTA. They come in various sizes and shapes, and many of them show features of insufficiency.
authors.affiliation: Royal Brisbane and Women's Hospital, Herston, 4029 Queensland, Australia.
authors.forename: Karin
authors.initials: K
authors.lastname: Steinke
authors.forename: Arash
authors.initials: A
authors.lastname: Moghaddam
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography; D001401:Azygos Vein / Q000000981:diagnostic imaging*; D015897:Comorbidity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging / Q000453:epidemiology; D012189:Retrospective Studies; D017678:Sex Distribution; D014057:Tomography, X-Ray Computed; D014689:Venous Insufficiency / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D055815:Young Adult