What is CT (Computed Tomography) venography used to diagnose?

CT Venography: Primary Diagnostic Applications

CT venography is primarily used to diagnose deep venous thrombosis (DVT) of the lower extremities, pelvis, and inferior vena cava, and is particularly valuable for detecting central venous thrombosis that ultrasound cannot adequately visualize. 1

Primary Indication: Deep Venous Thrombosis

CT venography serves as a critical diagnostic tool for DVT detection, with specific advantages over other modalities:

• CT venography provides accurate imaging of large pelvic veins and the inferior vena cava (IVC), areas that are difficult to assess with standard ultrasound 1
• The technique is as accurate as ultrasonography for diagnosing femoropopliteal DVT while offering superior visualization of central vessels 1
• CT venography can be combined with CT pulmonary angiography (CTPA) to evaluate both pulmonary embolism and DVT in a single examination, since DVT is the source of over 90% of pulmonary emboli 1

Upper Extremity Venous Thrombosis

CT venography is essential for diagnosing upper extremity DVT (UEDVT) in locations inaccessible to ultrasound:

• CT venography or MR angiography is needed to diagnose UEDVT located in the proximal subclavian vein, brachiocephalic vein, or superior vena cava (SVC) 1
• The technique provides more accurate assessment of isolated flow abnormalities associated with upper extremity thrombosis compared to ultrasound alone 1
• CT venography is particularly valuable for evaluating malignant superior vena cava syndrome 1

Combined PE and DVT Evaluation

When performed with CTPA, CT venography increases the sensitivity for detecting venous thromboembolic disease without reducing specificity:

• Adding CT venography to CTPA increases detection of venous thromboembolism by approximately 17-18% compared to CTPA alone 1, 2
• CT venography identifies DVT in approximately 0-6% of patients with negative CTPA results 1
• The technique identifies an additional 2-5% of patients with venous thromboembolic disease who would otherwise be missed 1

Technical Advantages

CT venography offers several technical benefits over conventional venography:

• The examination requires 80% less contrast material than conventional venography 3
• CT venography more clearly demonstrates thrombus extension into pelvic veins and IVC than conventional venography alone 3
• The technique involves injection of contrast media into an arm vein followed by helical CT imaging timed to coincide with opacification of the deep veins 1

Clinical Scenarios Favoring CT Venography

Specific clinical situations where CT venography is particularly valuable:

• When ultrasound results are negative or indeterminate but clinical suspicion for DVT remains high, CT venography is recommended as the next imaging modality 1
• For patients with suspected PE who have obvious signs of DVT, combined CTPA/CT venography can establish the diagnosis of venous thromboembolism in a single study 1
• In cancer patients with suspected central venous thrombosis, where ultrasound has known limitations for imaging pelvic veins and central vessels 1

Important Caveats

Key limitations to consider:

• CT venography requires administration of IV contrast, sharing this disadvantage with conventional venography but avoiding foot vein cannulation 1
• The technique requires relatively high concentrations of contrast agent, which may be problematic in patients with renal insufficiency 1
• Optimal scanning should extend from the calves to the iliac crests in patients suspected of venous thromboembolism 2
• The additional radiation exposure from CT venography must be weighed against diagnostic benefits, particularly in younger patients 1