Furthermore, particular cancer treatments (such as the use of central venous catheters for chemotherapy) may increase the risk of thrombosis further.Nephrotic syndrome, in which protein from the bloodstream is released into the urine due to kidney diseases, can predispose to thrombosis; this is particularly the case in more severe cases (as indicated by blood levels of albumin below 25 g/L) and if the syndrome is caused by the condition membranous nephropathy. Inflammatory bowel disease (ulcerative colitis and Crohns disease) predispose to thrombosis, particularly when the disease is active. Various mechanisms have been proposed.Pregnancy is associated with an increased risk of thrombosis of 2- to 7-fold. This probably results from a physiological hypercoagulability in pregnancy that protects against postpartum hemorrhage. This hypercoagulability in turn is likely related to the high levels of estradiol and progesterone that occur during pregnancy.Estrogens, when used in combined hormonal birth control and in menopausal hormone therapy (in combination with progestogens), have been associated with a 2- to 6-fold increased risk of venous thrombosis. The risk depends on the types of hormones used, the dose of estrogen, and the presence of other thrombophilic risk factors. Various mechanisms, such as deficiency of protein S and tissue factor pathway inhibitor, are said to be responsible.Obesity has long been regarded as a risk factor for venous thrombosis. It more than doubles the risk in numerous studies, particularly in combination with the use of oral contraceptives or in the period after surgery. Various coagulation abnormalities have been described in the obese.
Diagnosis
Tests for thrombophilia include complete blood count (with examination of the blood film), prothrombin time, partial thromboplastin time, thrombodynamics test, thrombin time and reptilase time, lupus anticoagulant, anti-cardiolipin antibody, anti-β2 glycoprotein 1 antibody, activated protein C resistance, fibrinogen tests, factor V Leiden and prothrombin mutation, and basal homocysteine levels. Testing may be more or less extensive depending on clinical judgement and abnormalities detected on initial evaluation.For hereditary cases, the patient must have at least two abnormal tests plus family history. Screening
There are divergent views as to whether everyone with an unprovoked episode of thrombosis should be investigated for thrombophilia. Even those with a form of thrombophilia may not necessarily be at risk of further thrombosis, while recurrent thrombosis is more likely in those who have had previous thrombosis even in those who have no detectable thrombophilic abnormalities. Recurrent thromboembolism, or thrombosis in unusual sites (e.g. the hepatic vein in Budd-Chiari syndrome), is a generally accepted indication for screening. It is more likely to be cost-effective in people with a strong personal or family history of thrombosis. In contrast, the combination of thrombophilia with other risk factors may provide an indication for preventive treatment, which is why thrombophilia testing may be performed even in those who would not meet the strict criteria for these tests. Searching for a coagulation abnormality is not normally undertaken in patients in whom thrombosis has an obvious trigger.