What are the diagnostic tests for lower extremity edema?

From the Guidelines

Lower extremity edema should be evaluated using a combination of clinical assessment and diagnostic tests, with the choice of test guided by the pretest probability of deep vein thrombosis (DVT) and the patient's overall clinical presentation, as recommended by the American Society of Hematology 2018 guidelines 1. The most recent and highest quality study, published in 2018, suggests that for patients at low risk of venous thromboembolism (VTE), D-dimer can be used as the initial test to reduce the need for diagnostic imaging 1.

Key Considerations

• The clinical assessment of pretest probability of DVT should guide the diagnostic process, with patients at low risk undergoing initial testing with D-dimer or ultrasound (US) of the proximal veins 1.
• Patients with moderate to high pretest probability should undergo initial testing with a highly sensitive D-dimer, proximal compression US, or whole-leg US 1.
• The American College of Radiology recommends US duplex Doppler as the preferred imaging modality for diagnosing proximal DVT, due to its high sensitivity and specificity 1.
• MR venography can be used as a noninvasive alternative to contrast catheter venography, especially in patients with suspected extrinsic venous compression or alternative diagnoses that mimic DVT 1.

Diagnostic Tests

• Pitting edema test: performed by pressing a finger firmly against the skin over a bony surface for 5 seconds and observing if an indentation remains after removing pressure.
• Stemmer's sign: involves pinching the skin at the base of the second toe; inability to pinch the skin suggests lymphedema.
• Kaposi-Stemmer sign: similar to Stemmer's sign but performed on the dorsum of the foot.
• Figure-of-eight measurement: uses a tape measure around the ankle in a specific pattern to quantify swelling.
• Homans' sign: calf pain with dorsiflexion to check for deep vein thrombosis.

Patient Evaluation

• Note the distribution, symmetry, and timing of edema onset to differentiate between various causes such as venous insufficiency, lymphedema, or systemic diseases.
• Bilateral edema evaluation should include cardiac, renal, and hepatic function tests as these conditions commonly cause fluid retention.

From the Research

Lower Extremity Edema Tests

• The evaluation of lower extremity edema should begin with a thorough history and physical examination, as well as laboratory tests such as a basic metabolic panel, liver function tests, thyroid function testing, brain natriuretic peptide levels, and a urine protein/creatinine ratio 2.
• Validated decision rules, such as the Wells and STOP-Bang criteria, can guide decision-making regarding the possibility of venous thromboembolic disease and obstructive sleep apnea, respectively 2.
• For patients with acute unilateral lower-extremity edema, a d-dimer test or compression ultrasonography can be used to evaluate for deep venous thrombosis 2, 3.
• Duplex ultrasonography with reflux can help diagnose chronic venous insufficiency in patients with chronic bilateral lower-extremity edema 2, 4.
• Lymphoscintigraphy can be performed if the diagnosis of lymphedema is unclear 2.
• A diagnostic algorithm that incorporates a systematic approach to the patient with leg swelling can provide an efficient pathway for the differential diagnosis of lower limb edema 5.
• The sequential use of complete duplex ultrasonography, ELISA D-dimer testing, and modified clinical Wells' score assessment is safe and effective for the exclusion and diagnosis of deep vein thrombosis and alternative diagnoses 4.
• Therapeutic options for venous disease and lymphedema include compression therapy, diuretics, Ruscus extract, and horse chestnut seed, among others 2, 6.