With this technique, proximal compression tourniquets are applied, and a series of overlapping radiographs are obtained following an iodine-containing contrast medium injection into a dorsal vein in the foot. DVT is present if a distinct filling defect is present in a deep vein, typically in the calf or thigh, but it can often extend to or involve more proximal veins, such as those in the pelvis. Less specific findings for DVT include an abrupt contrast cut- off, the absence of contrast filling, or the presence of collateral venous vessels. Although the techniques have evolved to catheter-directed venography using fluoroscopy, the risks and benefits are felt to be the same. MR Venography Lower Extremity and Pelvis MR venography (MRV) is a noninvasive alternative to contrast catheter venography. MRV does have inherent advantages over US, especially in its ability to delineate extravascular anatomy. MRV can help identify potential sources of extrinsic venous compression (ie, May-Thurner syndrome or a mass) that can be an underlying cause for DVT or suggest alternative diagnoses that mimic DVT. Suspected Lower Extremity DVT specificity, 95.2%) comparable to that of US for diagnosing proximal DVT [23]. CTV can also be incorporated into a comprehensive examination that includes pulmonary CT angiography for evaluating both pulmonary embolism and proximal DVT [26], but it should not be performed routinely in all patients who are being evaluated for pulmonary embolism [27]. There is little evidence to support the use of CTV to diagnose DVT; however, based on the published experience with pulmonary embolism, CTV may be considered a reasonable alternative to MRV for pelvic DVT or when US is nondiagnostic. Summary of Recommendations Variant 1: US duplex Doppler lower extremity is the recommended initial imaging examination for patients with suspected lower extremity DVT.
Suspected Lower Extremity Deep Vein Thrombosis. With this technique, proximal compression tourniquets are applied, and a series of overlapping radiographs are obtained following an iodine-containing contrast medium injection into a dorsal vein in the foot. DVT is present if a distinct filling defect is present in a deep vein, typically in the calf or thigh, but it can often extend to or involve more proximal veins, such as those in the pelvis. Less specific findings for DVT include an abrupt contrast cut- off, the absence of contrast filling, or the presence of collateral venous vessels. Although the techniques have evolved to catheter-directed venography using fluoroscopy, the risks and benefits are felt to be the same. MR Venography Lower Extremity and Pelvis MR venography (MRV) is a noninvasive alternative to contrast catheter venography. MRV does have inherent advantages over US, especially in its ability to delineate extravascular anatomy. MRV can help identify potential sources of extrinsic venous compression (ie, May-Thurner syndrome or a mass) that can be an underlying cause for DVT or suggest alternative diagnoses that mimic DVT. Suspected Lower Extremity DVT specificity, 95.2%) comparable to that of US for diagnosing proximal DVT [23]. CTV can also be incorporated into a comprehensive examination that includes pulmonary CT angiography for evaluating both pulmonary embolism and proximal DVT [26], but it should not be performed routinely in all patients who are being evaluated for pulmonary embolism [27]. There is little evidence to support the use of CTV to diagnose DVT; however, based on the published experience with pulmonary embolism, CTV may be considered a reasonable alternative to MRV for pelvic DVT or when US is nondiagnostic. Summary of Recommendations Variant 1: US duplex Doppler lower extremity is the recommended initial imaging examination for patients with suspected lower extremity DVT.