This is a condition in which blood clots form spontaneously in the deep veins of the lower or upper limbs. 

Risk factors for DVT development include:

  1. long-periods of immobility (e.g long-haul flights or travel journeys)
  2. after major surgery involving the limbs, pelvis or abdomen,
  3.  obesity,
  4. dehydration and major trauma to the limbs,
  5. have a genetic pre-disposition to blood clotting , causing DVT,
  6. abnormal blood vessel anatomy e.g May-Thurner syndrome or Paget-Schroetter Syndrome
  7. the presence of underlying cancer which can result in the blood being more prone to clotting (paraneoplastic syndrome).


Most cases of DVT are fortunately not life-threatening and can be treated with medication. These are usually those cases with DVT involving the below knee segment of the legs or the forearm of the upper limb. However, patients with DVT extending above knee or upper arm towards the heart may be in greater danger as the clots in the DVT can break off in pieces and travel into the heart and lungs (embolize) resulting in a serious condition known as Pulmonary Embolism (PE). This condition is life-threatening as it prevents oxygen transfer to the venous blood and is associated with significant mortality.


Patients with DVT can present with a swollen and tender limb. In the legs, it may start in the calf and then extend towards the thigh and groin. In the upper limbs, it can start in the forearm and extend upwards.

Patients can also present with a fast heartbeat (tachycardia) and shortness of breath, either in isolation or related to the limb swelling. This is a worrying sign as it indicates the presence of PE.


To prevent DVT from “economy class syndrome”, keep well-hydrated by drinking lots of water during a long-haul flight. Avoid excessive alcohol consumption.. Also avoid long-periods of immobility by getting out of the seat and walking around every 2 hours.

For patients about to undergo limb, pelvic or abdominal surgery, consider using anti-coagulation (blood thinning) drugs during the period before and after surgery.

The use of tight compression stockings can also prevent the formation of DVT.


Diagnosis is based on a high index of suspicion with a positive risk factor history coupled with positive ultrasound scans showing the presence of clots in the deep veins. Other associated investigations include a CT scan of the pulmonary arteries and a ventilation-perfusion scan if there is a suspicion of PE.

Other investigations include a blood screen for pro-clotting factors and tumour markers if there is underlying suspicion of cancer.


All patients with DVT must be stated on blood thinning medication (anti-coagulation) unless there is a good reason to withhold it (e.g prone to bleeding in the gut or recent bleeding stroke in the brain). The objective of the anti-coagulation is to prevent more new blood clots from forming. The body usually helps in dissolving the existing vein blood clots over time, sometime up to 6 months. As such, all patients should be on the anti-coagulation medication for up to 6 months.

If the DVT is extensive (e.g extending up the thigh and into the pelvic veins), it is sometimes necessary to use a combination of mechanical devices and special drugs to dissolve the clots. This process, known as thrombolysis, is usually done if the DVT is less than 2 weeks old and can be done as a minimally invasive procedure.  The thrombolysis is to prevent long-term problems associated with DVT such as the Post-Thrombotic Syndrome (PTS) and limb venous ulcers. Other additional procedures include the use of stents to keep the compressed veins open.

If there is evidence of severe PE, it may sometimes be needed to remove the blood clots in the lung through thrombolysis or open chest surgery.

Other adjunctive procedures to prevent clots that have broken off from reaching the lung veins include the insertion of metallic filters in the inferior vena cava (the largest vein in the abdomen, draining the legs) to trap loose clots.

For cases of upper limb DVT, in addition to clot thrombolysis, it may sometimes be necessary to remove the 1st rib to reduce the tightness and compression of the upper limb veins as it travels in the region around the shoulder.

Patients may also be required to wear compression stockings to help resolve the limb swelling.