IMPROVED RELIABILITY OF ULTRASONIC SURVEILLANCE OF ABDOMINAL AORTIC-ANEURYSMS

Objectives: Small abdominal aortic aneurysms (AAA) are usually managed conservatively by serial ultrasound examinations to assess size. The development of the size of the AAA will determine whether the patient is a candidate for surgery The precision of measurement is therefore o f considerable importance. The aim of this study was to evaluate the a ccuracy and the reproducibility of a newly developed echo-tracking ult rasonic system in the size evaluation of AAA. Design: Prospective stud y at a University Hospital. Material and methods: An echo-tracking ult rasound system with a 3.5 MHz transducer was used in 54 patients with AAA. Thirty-six patients had repeated measurements by one technician t o evaluate the intra-observer variability. In another 18 patients with aortic dilatation/AAA, the measurements were repeated by a second tec hnician in a blinded fashion with calculation of inter-observer variab ility. The reproducibility was evaluated both using linear regression and plots according to the method described by Bland and Altman. Resul ts: The mean diameter of tile aorta was 37 mm (range 21-51 mm). The co efficient of correlation of repetitive measurements with one observer teas r = 0.99 and with two observers r = 0.99. The intra-observer vari ability was 0.78 mm (S.D.) and the inter-observer variability 0.93 mm (S.D.). The intra- and inter-observer coefficient of variation (CV) wa s 2-3%. Conclusions: The newly developed echo-tracking ultrasonography seems at present to be the most accurate and reliable method to follo w the diameter of an abdominal aortic aneurysm detecting relevant chan ges in the diameter exceeding 2 mm (2 S.D.). Thus it fulfils the requi rements both for follow-up of conservatively managed AAAs and endovasc ularly treated aneurysms.