When symptoms of venous pathology are recognized or suspected, the underlying etiology can be rapidly assessed by visual examination according to patterns discussed in Chapter 5. Duplex ultrasound can confirm the physical examination via direct visualization of varicosities below the skin surface; however, careful diagnostic evaluation is necessary if one is to understand the particular venous hemodynamics of an individual patient. These tests are important to understand in terms of venous physiology. Although Duplex ultrasound can identify sites of valvular incompetence, photoplethysmography (PPG) and other forms of plethysmography offer a simple, reproducible technique to examine the physiologic significance of those findings and to correlate them with the patient’s symptoms. The historical importance of PPG is important enough to include in this text. It need not be reiterated that the continuous wave Doppler is analogous to the stethoscope, the plethysmographic test analogous to an electrocardiograph (EKG), and the duplex ultrasound equivalent to an echocardiogram. The availability of small, compact, high-resolution ultrasound machinery has made the Duplex ultrasound exam the new standard of care.
The performance and interpretation of diagnostic tests must be guided by knowledge of the pathophysiology underlying a patient’s clinical problem. For example, if a patient has signs and symptoms of pulmonary embolism (PE), failure to demonstrate deep venous thrombosis (DVT) (by any means) carries little clinical weight. In contrast, for a patient without signs of PE but with clinical signs of proximal DVT (pain and swelling of the leg extending well above the knee), the demonstration of a normal color-flow duplex examination is a reasonably reliable indicator of some other nonthrombotic etiology.
Blood tests are rarely helpful in the evaluation of venous pathology. Most patients with deep venous thrombosis and PE have normal protime (PT) and activated partial thromboplastin time (APTT). A low white blood cell (WBC) count lowers the likelihood of an infectious process and raises the likelihood of DVT or PE, but an elevated WBC count is nonspecific because both normal and elevated WBC counts are common in patients with deep venous thrombosis.1 Both chronic venous insufficiency (venous congestion due to reflux) and DVT can mimic leg cellulitis, and true cellulitis is a frequent complication of both conditions.2
As D-dimer is a breakdown product of the lysis of cross-linked fibrin clots, plasma D-dimer levels have been investigated as potential aids to the diagnosis of DVT and PE. The literature suggests that about 10 percent of patients with symptoms of PE and a negative D-dimer screen (level less than 500 ng/ml) will have a positive pulmonary angiogram, while about 30 percent of similar patients with a positive D-dimer screen will have a positive angiogram.3
Several important functional tests have proven in the past to be useful in helping to assess the condition of the ...