Value of Complete Full-length Lower Extremity Sonography in Patients Undergoing Computed Tomographic Pulmonary Angiography

OBJECTIVES: To evaluate the diagnostic yield of complete lower extremity venous sonography for diagnosing deep venous thrombosis (DVT) in patients undergoing computed tomographic (CT) pulmonary angiography for suspected pulmonary embolism (PE). METHODS: We retrospectively reviewed all cases of lower extremity venous sonography and CT pulmonary angiography performed within 1 day of each other (n = 147) in a tertiary care center. Indications for the studies performed, angiographic findings, sonographic findings, age, sex, inpatient/outpatient status, lower extremity symptoms, and treatment status were recorded. Prevalence rates and patient characteristics were compared by χ(2) and Fisher exact probability tests where appropriate. Multivariable logistic regression with acute PE as the outcome was performed for age, sex, interval between angiography and sonography, indication for angiography, inpatient/outpatient status, and venous sonographic findings. RESULTS: The prevalence of PE (23.8%) was similar to the prevalence of DVT (27.9%). Angiographic findings were not associated with the interval between angiography and sonography or inpatient/outpatient status. Acute DVT was more likely (P =.0009) when angiographic findings were positive (51.4%), but DVT prevalence was still substantial (20.5%) in patients with negative angiographic findings. Lower extremity symptoms were not associated with DVT in cases with negative angiographic findings (P =.48). Eighteen of the 23 patients with acute DVT and negative angiographic findings were treated. CONCLUSIONS: There is a high rate of DVT in a population undergoing CT pulmonary angiography for suspected PE even when PE is not diagnosed. Our data apply to a tertiary care institution, suggest a surveillance bias, and favor the utility of venous sonography in this population.