Internal or external wall diameter for abdominal aortic aneurysm screening?

A Thapar1, D Cheal, T Hopkins

  • 1Department of Vascular Surgery, Brighton & Sussex University Hospitals, Brighton, UK. a.thapar09@imperial.ac.uk

Insights

Abdominal aortic aneurysm (AAA) screening measurements of internal wall diameter underestimate aneurysm size by 6 mm compared to external wall measurements. This difference and greater variability in internal measurements may delay AAA detection and treatment.

Area of Science:

  • Vascular Surgery
  • Medical Imaging
  • Public Health Screening

Background:

  • The UK's national abdominal aortic aneurysm (AAA) screening programme measures internal wall diameter.
  • Current UK intervention criteria rely on external wall diameter measurements.
  • A discrepancy exists between these two measurement methods, necessitating clinical evaluation.

Purpose of the Study:

  • To determine the clinical significance of the difference between internal and external wall diameter measurements in abdominal aortic aneurysms.
  • To assess the impact of measurement methodology on AAA detection and treatment criteria.

Main Methods:

  • Fifty patients in an aneurysm surveillance program underwent ultrasound scans.
  • Two experienced vascular scientists performed measurements, blinded to each other's results.
  • Maximum anteroposterior internal and external wall diameters were measured.

Main Results:

  • A median difference of 6-7 mm was observed between internal and external diameters.
  • This difference was statistically significant (P < 0.0002).
  • External wall diameter measurements exhibited less interobserver variability (3 mm vs 6 mm).

Conclusions:

  • Internal wall diameter measurements used in AAA screening underestimate aneurysm size by approximately 6 mm.
  • Internal measurements show greater variability compared to external measurements.
  • Understanding these differences is crucial to prevent delays in AAA detection and treatment.
Abstract

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