Immobility which causes blood flow in the veins to be slow. Slow flowing blood is more likely to clot than normal flowing blood.
Long journeys, by any means of transport, where you sit still for long periods of time without being able to stretch your legs or move about.
Surgery where you are asleep. The anaesthetic can affect the muscles in the leg with the blood flow becoming slower increasing the risk of a blood clot. Certain types of surgery in the leg, knee and pelvis carry a higher risk of a DVT and all patients opting for elective surgery will need to be assessed before surgery and given anticoagulant medication (thromboprophylaxis) to reduce this risk.
An illness or injury that causes immobility increases the risk. Fractures that require a hard plaster cast can increase risk. Seriously ill patients may be anaesthetised to help aid recovery and therefore will be unable to move voluntarily
THROMBOPHILIA – conditions that cause the blood to clot more easily than normal can increase risk.
Antiphospholipid syndrome (APS) or Hughes Syndrome is a disease of the immune system that affects the blood. Sometimes called ‘sticky blood’ because the blood is prone to forming clots. It can cause serious problems in pregnancy as a clot can develop in the placenta and may result in a miscarriage or premature birth. APS sufferers need to be treated with anticoagulant therapy.
Antithrombin Deficiency and Factor V Leiden are types of rare genetic conditions and can cause the blood to clot more easily than normal. You are more at risk if you have close family members who have had a history of blood clots.
Damage to the inside lining of the vein caused by a DVT can increase the risk of another clot forming in future. Vasculitis ( inflammation of the vein wall) and some chemotherapy drugs can cause damage. Insertions of needles can damage veins and this may occur after treatment with a drip (intravenous catheter) whilst in hospital.
Nephrotic syndrome where the filters in the kidney become 'leakey' and large amounts of protein leak from the blood into your urine
Cancer. Sometimes a person presents with a DVT without a diagnosis of cancer. Investigations may show that cancer is the underlying cause
Contraceptive pill or Hormone Replacement Therapy (HRT) which contains oestrogen can cause the blood to clot more easily and women taking these treatments will have an increased risk
Pregnancy. Approximately 1 in 1000 pregnant women will have a DVT whilst they are pregnant, or within six months after giving birth
There has recently been some speculation that sitting at your desk for long periods of time may also increase risk of a DVT or ‘eclot’ and blood clots are now being seen in younger people who play video games over long periods of time restricting mobility
Age – Your risk increases over 60 years especially if there is poor mobility or you have a serious illness such as cancer
It should also be noted that some people will have a DVT for no apparent reason.