title: Deep venous reflux definitions and associated clinical and physiological significance.
abstract: BACKGROUND
  Deep venous reflux (DVR) is often a poorly defined clinical entity. The extent of DVR that must occur for it to be clinically and hemodynamically important is not clear and is usually confounded by the presence of superficial venous reflux. This study aims to investigate the effect of the extent of DVR on clinical and hemodynamic parameters while controlling for the presence of superficial reflux.
  
  
  METHODS
  We performed a cross-sectional study, using a prospectively designed data set obtained from patients presenting to a vascular laboratory for lower limb venous assessment. Age, gender, duplex ultrasound assessment of the deep and superficial systems, CEAP clinical class, and venous filling index (VFI) measurements were obtained. A classification of axial DVR is described, based on the level of continuous reflux occurring in the vertical axis as detected by duplex ultrasound: axial 0 (no deep reflux), axial 1 (common femoral vein only), axial 2 (to any level of the femoral vein), axial 3 (to the level of the popliteal vein), and axial 4 (into the calf veins) A subset of segmental reflux is also defined.
  
  
  RESULTS
  This study included 3122 limbs from 2349 subjects. Limbs with increasing axial level were more likely to have CEAP 4-6 (axial 0: 294 [37.2%]; axial 1: 520 [41.6%]; axial 2: 82 [41.2%]; axial 3: 92 [59.7%]; axial 4: 148 [64.9%], P value for trend <.0001). This relationship remained highly significant following adjustment for superficial reflux and demographic variables. Compared with limbs with no DVR, the adjusted odds ratio for having CEAP 4-6 was 2.10 (1.25-3.51; P < .0048) for limbs with axial level 3 and 3.07 (1.94-4.88, P < .0001) for limbs with axial level 4. Similarly after adjustment, predicted mL/s increases in VFI were significant (P < .0001) for level 1 (1.19 [1.08-1.31]), level 3 (1.53 [1.31-1.78]), and level 4 (1.74 [1.51-1.95]). Segmental reflux, when extensive, also contributed to the risk of more severe disease.
  
  
  CONCLUSIONS
  Deep axial reflux to the level of the knee and calf is associated with more severe venous disease and greater VFI, independently of reflux in the superficial system. A system of classification of DVR is recommended.
authors.affiliation: Department of Surgical Sciences, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: Kah Heng
authors.initials: KH
authors.lastname: Lim
authors.affiliation: Department of Surgical Sciences, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: Gerry
authors.initials: G
authors.lastname: Hill
authors.affiliation: Department of Surgical Sciences, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: Greg
authors.initials: G
authors.lastname: Tarr
authors.affiliation: Department of Surgical Sciences, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand. Electronic address: andre.vanrij@stonebow.otago.ac.nz.
authors.forename: Andre
authors.initials: A
authors.lastname: van Rij