title: Clinical implications of non-contrast-enhanced computed tomography for follow-up after endovascular abdominal aortic aneurysm repair.
abstract: BACKGROUND
  There is growing concern over the long-term radiation exposure from serial computed tomographic (CT) scan follow-up after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs). Screening for endoleaks with non-contrast-enhanced volumetric CT has been shown to significantly reduce radiation doses. We evaluated the use of NCT as the primary method of follow-up after EVAR of AAAs.
  
  
  METHODS
  Our institutional post-EVAR CT protocol consisted of contrast-enhanced CT angiography (CTA) 1 month after repair, followed by NCT at 3 or 6 and 12 months, and annually thereafter. At each follow-up scan, immediate 3-dimensional volume analysis was performed. If the volume change was <2%, NCT follow-up was continued. If the volume increased by ≥2% on nonenhanced images, contrast-enhanced CT was performed immediately to identify potential endoleaks. All images were reviewed by an experienced cardiovascular radiologist. End points included identification of endoleak, reintervention, and rupture.
  
  
  RESULTS
  Over a 7-year period, 126 patients were followed. Serial CTA was performed in 59 patients, while 67 patients were followed with the NCT protocol. The mean follow-up was 2.07 years. There were no differences in age, sex, or initial aneurysm volume or size. There were 35 total endoleaks identified. Twenty of these were early endoleaks (<30 days post-EVAR). The remaining 15 leaks were late in nature (10 in the contrast group and 5 in the noncontrast group; P=0.17). NCT aneurysm sac volume changes prompted contrasted studies in all 5 late leaks. The mean volume change was 11.2 cm3, an average change of 5.88%. These findings were not significantly different than the late leaks found by routine contrast studies (8.9 cm3; 4.98% [P=0.58]). There were no delayed ruptures or emergent reinterventions in the NCT group.
  
  
  CONCLUSIONS
  Serial NCT appears to be safe and effective as the sole means of follow-up after EVAR for AAAs. AAA volume increases of ≥2% should prompt further contrast-enhanced CT imaging. Changes of <2% can be safely followed with serial NCT. This protocol requires dedicated cardiovascular radiologist involvement, and patients should be retained in the radiology suite until real-time image evaluation can be completed.
authors.affiliation: Department of Surgery, Division of Vascular Surgery, School of Medicine and Public Health, University of Wisconsin, Madison, WI.
authors.forename: Joseph Louis
authors.initials: JL
authors.lastname: Bobadilla
authors.forename: Pasithorn A
authors.initials: PA
authors.lastname: Suwanabol
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
authors.forename: Myron A
authors.initials: MA
authors.lastname: Pozniak
authors.forename: Thorsten A
authors.initials: TA
authors.lastname: Bley
authors.forename: Girma
authors.initials: G
authors.lastname: Tefera
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000601:surgery*; D001019:Aortic Rupture / Q000000981:diagnostic imaging* / Q000628:therapy; D001027:Aortography / Q000379:methods*; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects; D057867:Endoleak / Q000000981:diagnostic imaging* / Q000628:therapy; D057510:Endovascular Procedures / Q000009:adverse effects; D005260:Female; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D011829:Radiation Dosage; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome