A deep-vein thrombosis (DVT) is a blood clot that forms within the deep veins usually of the leg but can occur in the veins of the arms and the mesenteric and cerebral veins. Deep-vein thrombosis is a common and important disease. It is part of the venous thromboembolism disorders which represent the third most common cause of death from cardiovascular disease after heart attacks and stroke. Even in patients who do not get pulmonary emboli, recurrent thrombosis and "post-thrombotic syndrome" are a major cause of morbidity.
Following are the risk factors and are considered as causes of deep venous thrombosis:
Increased Risk of Coagulation
Incidence and prevalence: Deep-vein thrombosis and pulmonary emboli are common and often "silent" and thus go undiagnosed or are only picked up at autopsy. Therefore their incidence and prevalence are often underestimated. It is thought the annual incidence of DVT is 80 cases per 100,000 with a prevalence of lower limb DVT of 1 case per 1000 population. Annually in the United States, more than 200,000 people develop venous thrombosis; of those, 50,000 cases are complicated by pulmonary embolism.
Age: Deep-vein thrombosis is rare in children and the risk increases with age, most occurring in the over 40s.
Gender: There is no consensus about whether there is a sexual bias in the incidence of DVT.
Ethnicity: There is evidence from the USA that there is an increased incidence of DVT and an increased risk of complications in African Americans and white people when compared to Hispanics and Asians.
Associated diseases: In the hospital, the most commonly associated conditions are a malignancy, congestive heart failure, obstructive airways disease and patients undergoing surgery.
According to the Virchow's triad, the following are the main pathophysiological mechanisms involved in DVT:
Thrombosis is a protective mechanism which prevents loss of blood and seals off damaged blood vessels. Fibrinolysis counteracts or stabilizes the thrombosis. The triggers of venous thrombosis are frequently multifactorial, with the different parts of the triad of Virchow contributing in varying degrees in each patient, but all result in early thrombus interaction with the endothelium. This then stimulates local cytokine production and causes leukocyte adhesion to the endothelium, both of which promote venous thrombosis. Depending on the relative balance between the coagulation and thrombolytic pathways, thrombus propagation occurs. DVT is commonest in the lower limb below the knee and starts at low-flow sites, such as the soleal sinuses, behind venous valve pockets. 
As per the NICE guidelines following investigations are done:
Deciding how to investigate is determined by the risk of DVT. The first step is to assess the clinical probability of a DVT using the Wells scoring system.
Treatment of DVT aims to prevent pulmonary embolism, reduce morbidity, and prevent or minimize the risk of developing the post-thrombotic syndrome.
The cornerstone of treatment is anticoagulation. NICE guidelines only recommend treating proximal DVT (not distal) and those with pulmonary emboli. In each patient, the risks of anticoagulation need to be weighed against the benefits.
Following are differential diagnoses of deep venous thrombosis:
The severity of the disease is classified as
Many DVTs will resolve with no complications.
Post-thrombotic syndrome occurs in 43% 2 years post-DVT (30% mild, 10% moderate, and severe in 3%).
Risk of recurrence of DVT is high (up to 25%).
Death occurs in approximately 6% of DVT cases and 12% of pulmonary embolism cases within one month of diagnosis.
Early mortality after venous thromboembolism is strongly associated with the presentation as pulmonary embolism, advanced age, cancer and underlying cardiovascular disease.
The following are the two major complications of DVT;
DVTs occur in many hospitalized patients, and one of the most feared complications is a pulmonary embolus. DVTs also result in longer admission to the hospital and drug treatment that can last 3-9 months- all of which adds to the cost of healthcare. Thus, today, the focus is on the prevention of DVT. Besides physicians, both nurses and pharmacists are vital in educating patients about DVT prophylaxis. In fact, nurses are the first professionals to encounter patients being admitted to the hospital and it is here that prevention of DVT starts. Nurses need to educate the patients on the importance of ambulation, being compliant with compression stockings, and prescribed anticoagulation medications. In both the operating room and post surgery, nurses play a key role in reminding physicians for the need of DVT prophylaxis. Each hospital has its own guidelines on DVT prophylaxis and treatment and all healthcare workers should follow them. Once a DVT has developed, the pharmacist should be familiar with the current anticoagulants and their indications. Plus, the pharmacist must educate the patients on the need for treatment compliance and the need to undergo regular testing to ensure that the INR is therapeutic. (Level V)
Today close to 300,000 patients die from a pulmonary embolus each year in the US alone. Despite countless guidelines and education of healthcare workers, DVT prophylaxis is often not done. The fact is that DVT is preventable in the majority of patients and the onus is on healthcare workers to be aware of the condition. For those who do develop a DVT and survive, post-thrombotic phlebitis is a lifelong sequela, which has no ideal treatment.  (Level V)