**4. Conclusion**

The incidence of deep venous thrombosis is increasing, not just in the lower limb but also within the deep veins of the upper limb, where malignancy and central venous catheter placement are the major precipitating factors. Ultrasound provides a rapid and readily available assessment, and can be portably used at the bedside in critically ill patients. There is however limitations to ultrasound, particularly the poor visualisation of below knee clot. In high risk patients, a short interval repeat scan is indicated to exclude the 25% of such clots which can propagate above the knee.

The iliac veins within the pelvis are also inaccessible to ultrasound in almost every patient. If DVT is strongly suspected within the pelvis, MRI should be considered. This modality has seen the greatest advancements in recent times, with current protocols able to visualise the venous system in very high spatial resolution. CT angiography of the limbs, whilst sensitive and easily incorporated into routine CT pulmonary angiograph in suspected PE, should be avoided in view of the radiation burden. The major advantage of MRI is the lack of radiation exposure. MRI will almost certainly feature more commonly in DVT evaluation in the near future with new "blood pool" contrast agents allowing a comprehensive examination for PE and DVT in the same scan. One specific application is in relatively young patients with abnormal CXR precluding a V/Q scan. However, CT is currently the "gold standard" for diagnosing PE.

There are a number of endovascular treatment options in DVT which aim to achieve thrombus removal, restoring patency and potentially limiting the acute complications associated with DVT. It is important to appreciate there are limitations to these treatments, with a relative lack of randomised controlled trials evaluating their true efficacy. They should however be given consideration in selected patients as outlined above.
