Published Tue, 2012-02-14 16:05; updated 3 years ago.
Deep vein thrombosis (DVT) is a blood clot in one of the deep veins in the body.
If a piece of that clot breaks off into the bloodstream and blocks one of the blood vessels in the lungs, the outcome can be death.
That is the ultimate cause of concern - but many people are concerned about the effect of DVT on their appearance.
When someone has DVT it can cause swelling and redness in the affected leg.
"It goes a kind of dusky colour," says Lisa Carroll, lead on VTE in urgent care, University Hospital of North Staffordshire NHS Trust.
"It goes kind of mottled because there are obstructions in the blood flow."
Dr Jessica Arrowsmith, a Birmingham GP, says: "Many of my patients are more concerned about the change in the appearance of their leg than anything else."
The good news is that for most people the change in appearance is not permanent.
Someone with DVT is treated with an anticoagulant, which thins the blood and helps prevents new clots from forming.
In a straightforward case, the blood will then breakdown the clot and normal blood flow will be resumed.
"It takes about six to eight weeks," says Lisa. "Most people then find their leg goes back to normal."
The exception is when someone has chronic DVT and develops post-thrombotic syndrome.
This is where the blood clot in the vein diverts the flow of blood to other veins, which are less efficient, and which causes an increase in pressure in the tissues of the calf, swelling, discoloration and pain.
For women, the need to wear compression stockings for at least two years after having DVT can be just as distressing as it can inhibit them from wearing a skirt.
While it would be misleading to assume that all DVT can be avoided, it is well worth taking the steps to minimize the risk of getting a clot.
Image courtesy of James Heilman
Due for review February 2013