Venography is an invasive study whereby contrast dye is injected into the leg veins. It is considered a definitive test for DVT. Diagnosis of DVT is made if an intraluminal-filling defect is noted. Furlan and Fehlings (2007) note that:

Although contrast venography is considered as the gold standard for investigation of symptomatic or asymptomatic DVT, venography has been considered an unsuitable tool for routine assessment of asymptomatic DVT due to its invasive nature, potential complications, technical issues and costs [Kelly et al. 2001; Tapson et al. 1999; Zierler 2004].