From the Guidelines
CT venography (CTV) is the most appropriate type of CT scan to clarify suspected femoral deep vein thrombosis (DVT). This recommendation is based on the most recent and highest quality study available, which suggests that CTV is as accurate as ultrasound in diagnosing femoropopliteal DVT and may be superior in detecting thrombus in large pelvis veins and the inferior vena cava 1.
Key Points to Consider
- CTV provides excellent visualization of the deep venous system from the inferior vena cava down through the femoral veins and can clearly demonstrate filling defects characteristic of DVT.
- While ultrasound remains the first-line imaging modality for suspected DVT due to its availability, lack of radiation, and high sensitivity for proximal DVT, CTV offers advantages in cases where ultrasound results are equivocal, when there is poor acoustic window, or when evaluation of the pelvic veins and inferior vena cava is needed.
- CTV also allows simultaneous assessment of surrounding soft tissues and can identify alternative diagnoses that may mimic DVT symptoms.
- Patients should be screened for contraindications to iodinated contrast including renal impairment and allergy history prior to undergoing this examination.
Comparison with Other Imaging Modalities
- Magnetic Resonance Venography (MRV) with contrast is another option for diagnosing DVT, particularly in cases where ultrasound is nondiagnostic, but it has higher cost, longer imaging times, and limited availability in some practice settings 1.
- Standard invasive venography has largely been replaced by less invasive methods such as ultrasound and MRV, which provide equivalent accuracies 1.
Clinical Implications
- Early initiation of anticoagulation should be considered in patients with a high suspicion of DVT while awaiting results from imaging studies, especially if there are no contraindications to anticoagulation 1.
- A comprehensive medical history and physical examination, complete blood count with platelet count, prothrombin time, activated partial thromboplastin time, fibrinogen, and liver and kidney function tests should be performed as part of the workup for suspected DVT 1.
From the Research
Computed Tomography (CT) for Femoral Deep Vein Thrombosis (DVT)
- The type of CT that would clarify femoral DVT is indirect multidetector CT venography 2.
- Indirect MDCT venography has been shown to be as accurate as sonography in the diagnosis of femoropopliteal DVT, with a sensitivity and specificity of 100% 2.
- CT venography can further reveal thrombus in large pelvis veins and the inferior vena cava, an important advantage over sonographic screening for DVT 2.
- Chronic-stage DVT of the lower extremities can be diagnosed using indirect CT venography, which can show luminal obliteration, decreased caliber, residual thrombi, fibrotic bands, ipsilateral muscle enlargement, ipsilateral subcutaneous edema, and superficial collateral vein development 3.
Comparison with Other Diagnostic Methods
- Duplex ultrasound is also an accurate non-invasive test in the diagnosis of acute femoro-popliteal thrombosis, with a sensitivity of 90.6% and specificity of 94.6% 4.
- Duplex scanning is superior to contrast venography in the detection of non-occlusive and deep femoral vein thrombosis 4.
- Non-contrast-enhanced magnetic resonance imaging (MRI) can also be used to diagnose acute DVT, with a sensitivity of 79% and specificity of 94.2% 5.
- MRI can detect more non-filling thrombi in the femoral vein than ultrasound 5.