title: Below-knee deep vein thrombosis: an opportunity to prevent pulmonary embolism?
abstract: BACKGROUND
  The prevention of venous thromboembolic disease following trauma is a priority. In contrast to above-knee deep vein thrombosis (AKDVT), the management of below-knee deep vein thrombosis (BKDVT) is controversial because the risk of pulmonary embolism (PE) has not been firmly established. We hypothesized that BKDVT and AKDVT have an equivalent risk for PE in trauma patients.
  
  
  METHODS
  We identified patients from July 2006 to December 2011 with BKDVT and/or AKDVT diagnosed by lower extremity duplex ultrasound (LEDU) and patients with PE diagnosed by computed tomography angiogram. Time of DVT onset, progression or regression, and time of PE were assessed. The BKDVT and AKDVT patient groups were defined by the location of DVT on initial LEDU. The use of therapeutic anticoagulation and inferior vena cava filter (IVCF) were compared between the BKDVT and AKDVT groups.
  
  
  RESULTS
  Of 11,330 patients evaluated during the study period, 2,881 (25.4%) underwent surveillance LEDU, and 251 (8.7%) of these patients had DVT alone or associated with PE. BKDVT progressed to AKDVT and/or PE in 21 patients (12.9%). PE rates were 6.1% and 1.1% in the BKDVT and AKDVT groups, respectively (p = 0.1). There was a higher rate of therapeutic anticoagulation and/or IVCF in the AKDVT group than in the BKDVT group (86% vs. 24%, p < 0.0001).
  
  
  CONCLUSIONS
  In our study population, BKDVT was associated with a higher rate of PE compared with AKDVT, which was likely secondary to the treatment of AKDVT. Because BKDVT progressed to AKDVT or PE in 1 of 8 patients, BKDVT should not be ignored in trauma patients. Aggressive chemical prophylaxis and perhaps therapeutic anticoagulation or IVCF should be considered in patients with BKDVT. Further investigation is warranted to confirm these conclusions.
  
  
  METHODS
  Therapeutic study, level IV.
authors.affiliation: From the Trauma Service, Scripps Mercy Hospital, San Diego, California.
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Olson
authors.forename: Ashley L
authors.initials: AL
authors.lastname: Zander
authors.forename: Jan-Michael
authors.initials: JM
authors.lastname: Van Gent
authors.forename: Steven R
authors.initials: SR
authors.lastname: Shackford
authors.forename: Jayraan
authors.initials: J
authors.lastname: Badiee
authors.forename: C Beth
authors.initials: CB
authors.lastname: Sise
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sise
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000209:etiology / Q000517:prevention & control*; D012189:Retrospective Studies; D012307:Risk Factors; D016306:Vena Cava Filters; D020246:Venous Thrombosis / Q000150:complications* / Q000209:etiology; D014947:Wounds and Injuries / Q000150:complications
chemical_list: D000925:Anticoagulants