The Impact of Body Mass Index on Lower Extremity Duplex Ultrasonography for Deep Vein Thrombosis Diagnosis

Background: This study aimed to determine the body mass index (BMI) at which duplex ultrasonography does not accurately detect deep vein thrombosis. Methods: This is a retrospective review of all patients who underwent lower extremity venous duplex examination at a single institution, tertiary vascular laboratory from January 2011 to June 2011. Demographics, BMI, operator years of experience, and duplex ultrasound study quality were recorded. Duplex ultrasound study quality was divided into "adequate" or "inadequate." Results: A total of 495 patients were included in this study, of which 435 (88%) patients were adequate and 60 (12%) inadequate. One hundred ninety-eight (40%) patients of the overall study cohort were men and 297 (60%) women. Limited studies were performed in 21 (11%) men and 39 (13%) women (P = 0.48). There was an inverse relationship between the years of operator experience and the percent of studies classified as limited (P < 0.01). The mean BMI of patients in the adequate group versus the inadequate group was 30.3 +/- 8.9 (median 28.9) versus 39.8 +/- 15.1 (median 38.4), respectively (P < 0.0001). Univariate analysis identified tech A (least experience) (3x) and increased BMI > 40 (6x) as independent variables associated with having a limited duplex ultrasound study. Conclusion: These results suggest that patients with BMI > 40 may require an alternative imaging modality to objectively diagnose the presence of venous thromboembolism as an increased BMI is associated with an indeterminate study.