# Investigating the necessity of bilateral common femoral vein ultrasound in patients with unilateral symptomatic deep venous thrombosis

## TL;DR

This study examines whether checking the opposite leg's vein is needed when diagnosing blood clots in one leg, finding it may not be necessary.

## Contribution

The study provides evidence that bilateral common femoral vein ultrasound may not be required for unilateral DVT evaluation.

## Key findings

- No cases of bilateral DVT were found in the study cohort.
- No DVT was isolated to the contralateral asymptomatic common femoral vein.
- Unilateral ultrasound suffices in most cases without missing DVT.

## Abstract

Venous duplex ultrasound (VDUS) examinationis the accepted initial imaging study to rule out lower extremity deep venous thrombosis (DVT). In accordance with the Intersocietal Accreditation Commission vascular laboratory policies, many institutions require technicians to additionally assess the asymptomatic contralateral common femoral vein (CFV). There is conflicting literature on whether this policy is needed. Therefore, the aim of this study was to investigate the utility of examining the asymptomatic contralateral CFV in patients undergoing a unilateral lower extremity VDUS to rule out DVT by (1) defining the prevalence of DVT in the contralateral asymptomatic limb and (2) identifying risk factors that predispose patients to develop a DVT in the asymptomatic limb.

We retrospectively reviewed the results of all unilateral lower extremity VDUS examinations performed on inpatients and outpatients from January 2023 to July 2023. Patient data, including age, sex, symptoms, risk factors for DVT, and indications for the study, were collected. The primary outcome was the frequency of DVT in the asymptomatic contralateral CFV. Categorical and continuous data were compared using the χ2 and Student t tests, respectively. For all tests, a P value of less than .05 was considered statistically significant.

We identified 371 patients (170 inpatient and 201 outpatient) with unilateral DVT symptoms who underwent VDUS examination during the study period. Right leg symptoms were present in 186 patients (50%) and left leg symptoms were present in 185 patients (50%). The overall incidence of acute DVT in the symptomatic limb was 17% (17.4% outpatient vs 16.5% inpatient; P = .NS). Outpatients were more likely to have superficial venous thrombosis (7.0% vs 0.6%; P = .002) and chronic venous changes (25.4% vs 1.2%; P < .001) in the symptomatic limb. Of the DVTs in the symptomatic limb, 59% were documented in the calf veins, 25% in the proximal veins, and 16% in both the proximal and calf veins. There were no incidences of bilateral DVT in our cohort. Moreover, none of the patients had a DVT isolated to the contralateral CFV.

Scanning the asymptomatic contralateral CFV may not be necessary for patients undergoing unilateral VDUS examination for symptomatic DVT, regardless of thrombotic risk factors. A single-extremity study suffices in most cases; if implemented, this strategy will improve vascular laboratory efficiency and decrease costs without a decrease in DVT detection.