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Chapter 112. Venous Thrombosis (Part 4)

Tham khảo tài liệu 'chapter 112. venous thrombosis (part 4)', y tế - sức khoẻ, y học thường thức phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 112. Venous Thrombosis Part 4 Deep Vein Thrombosis The signs and symptoms of DVT such as swelling pain redness superficial venous dilatation and Homan s sign pain in the calf or behind the knee on dorsiflexion of the ankle are nonspecific and consequently insufficient for ruling the disease in or out. The classic gold standard is contrast venography. Although very accurate this method requires radiologic facilities and expertise and is invasive and sometimes uncomfortable for the patient. Ultrasonography with noncompressibility of the vein as the sole criterion has largely replaced contrast venography. The investigation is limited to the femoral vein in the groin and the popliteal vein in the popliteal fossa. This method has a very high sensitivity and specificity 95-100 in symptomatic patients for proximal DVT. For isolated DVT in the calf veins the method is less accurate. This latter characteristic of compression ultrasonography explains the necessity of repeating the test after 1 week in those patients with an initial normal test result in order to detect extending calf thrombi. However the first objective of the diagnostic workup was to rule out DVT quickly and safely. For this purpose the combination of the assessment of clinical probability and the measurement of the D-dimer blood concentration has been shown to be very useful. The clinical probability can be best assessed by the rule shown in Table 111-2 which results in a classification of either DVT likely or DVT unlikely. D-Dimer is a degradation product of crosslinked fibrin and therefore concentrations of D-dimer below a certain cut-off level are considered to indicate the absence of thrombosis. Elevations of D-dimer in patients 70 years who do not have thrombosis make the test less useful in this population. Table 111-2 Clinical Decision Rule for Diagnosing Thrombosis Decision rule for clinically suspected deep vein thrombosis DVT Points Active cancer patient receiving treatment for cancer .