الفهرس 
Anatomy of lower limb venous systemOnly 14 pages are availabe for public view
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Abstract
Acute thrombosis of the deep veins of the lower extremity remains one of the most significant public health problems.
The complications of acute venous thromboembolism (VTE) including deep venous thrombosis (DVT), pulmonary embolism (PE), and the postthrombotic syndrome are the most common preventable cause of hospital death1 and a source of substantial long-term morbidity.
The incidence of VTE varies with the population studied the use of thromboprophylaxis, the intensity of screening, and the accuracy of the diagnostic test employed.
VTE is a devastating acute disease process, but it may be manifested chronically. Nearly 30% of patients have a recurrence in a 10-year time span. Recurrences are more likely with the same event type as that of the incident event, that is to say those who initially developed a PE are more likely to develop another PE instead of a DVT.
DVT occurring in the setting of a recognized risk factor is often defied as a secondary event; in the absence of risk factors, it is termed primary or idiopathic.
New therapeutics extend the ability to safely treat acute thrombotic episodes to prevent rethrombosis, and to prevent DVT in high-risk patients.
The clinical manifestations of acute DVT vary from an absence of symptoms and signs to the dramatic presentation of phlegmasia cerulea dolens and venous gangrene. Such broad variation is a result of multiple pathologic processes with different timing and severity occurring during an acute thrombotic episode.
D-dimer is a degradation product resulting from proteolysis by plasmin of cross-linked fibrin. Therefore, its elevated levels signify that fibrinolysis of complexed fibrin is taking place.
Diagnostic properties of D-dimer vary substantially depending on the assay used for its detection. Currently used assays differ in the specificity of antibody to various binding sites on the D-dimer molecule, in units of measurements, and in reference values. Their sensitivity for DVT diagnosis ranges from 60% to 96%.
In general, the sensitivities range from 44% to 72% for DVT and 44% to 70% for PE. While a negative D-dimer test has an excellent negative predictive value, a positive test is neither specific nor necessarily diagnostic for DVT, as numerous other medical conditions may also elevate D-dimer levels. Elevated levels of D-dimer are especially common in patients with myocardial ischemia, sepsis, and postoperative states without DVT.
Sonography is now the primary modality for the evaluation of DVT, mainly due to its accuracy, portability, and lack of ionizing radiation.
Ultrasound permits direct visualization of the thrombus, as well as documentation of altered vascular hemodynamics by Doppler.
Absence of blood flow, lack of venous phasic flow, and diminished response to Valsalva maneuvering or augmentation by calf compression are all associated Doppler findings characteristic of DVT. The accuracy of ultrasound exceeds 95% in many studies.
Multidetector CT venography has been investigated as an alternative means of directly visualizing clot in the venous system of the leg, thigh, and pelvis. Using foot venapuncture and contrast injection to opacify the leg veins in a manner similar to conventional leg venography, helical CT can provide diagnostic images of the venous system.
DVT of the legs may be divided into three types: namely, calf DVT involving the infrapopliteal venous system, proximal DVT involving the proximal leg veins up to the inguinal ligament, and iliofemoral DVT involving proximal DVT that extends above the inguinal ligament. This classification is critically important because the incidence of PE, post thrombotic syndrome (PTS), and treatment approach varies.
The single most important factor in prevention of VTE is the identification of patients at risk. Most available methods to prevent VTE are either mechanical aiming to improve venous flow and reduce stasis, or pharmacologic based on agents that act as anticoagulants to counteract hypercoagulability.
The objectives for treatment of acute DVT are to reduce morbidity, prevent thrombus extension, early recurrence, and death from PE.
Patients with VTE should be treated with anticoagulants as soon as the diagnosis is confirmed by objective imaging techniques. However, if the clinical suspicion is very high, treatment should be initiated until the diagnosis can be confirmed.
Intravenous or subcutaneous unfractionated heparin and subcutaneous LMWHs, The current recommended approach is to start heparin or LMWH and VKAs together at the time of diagnosis, and to overlap them for 5 to 10 days, discontinuing unfractionated heparin or LMWH when the prothrombin time expressed as the INR is within the target range (2.0-3.0) for two consecutive days.
There is a large body of evidence supporting the rationale for a strategy of thrombus removal, especially in patients with iliofemoral DVT. When a strategy of thrombus removal is successful, venous patency is restored, valve function is maintained, QoL is improved, and the risk of recurrence is reduced.
A growing body of evidence suggests that catheter-directed thrombolysis (CDT) is of benefit, especially in patients with iliofemoral DVT.
Pharmacomechanical techniques have been shown to improve outcomes compared with CDT using the drip technique alone. Pharmacomechanical techniques have shortened treatment times, reduced doses of lytic agent, and reduced length of intensive care unit (ICU) and hospital stays.
Contemporary venous thrombectomy for iliofemoral venous thrombosis offers effective short- and long-term outcomes with relatively few complications.
The principles of venous thrombectomy are those of basic vascular surgical techniques: remove the thrombus; provide unobstructed outflow from the iliofemoral venous segment and unobstructed inflow from the infrainguinal venous segment; correct any underlying lesions; and prevent re-thrombosis.