What are the diagnostic workups for edema in the lower extremities?

From the Guidelines

The diagnostic workup for edema in the lower extremities should begin with a thorough medical history and physical examination, followed by laboratory tests and imaging studies, with duplex ultrasound of the legs being the preferred initial imaging modality to rule out deep vein thrombosis 1. The initial evaluation should include assessment of vital signs, especially blood pressure, and examination of the swollen areas for pitting, skin changes, and temperature.

• Laboratory tests are essential, including:
  • Complete blood count
  • Comprehensive metabolic panel (to check kidney and liver function)
  • Urinalysis to detect protein that might indicate kidney disease
• Thyroid function tests may be ordered as hypothyroidism can cause edema
• If heart failure is suspected, brain natriuretic peptide (BNP) levels should be checked Imaging studies often include:
• Duplex ultrasound of the legs to rule out deep vein thrombosis
• Possibly chest X-ray or echocardiogram if cardiac causes are suspected In some cases, additional tests like CT scans, MRI, or lymphoscintigraphy may be necessary to evaluate for conditions like lymphedema 1. The workup should be tailored to the patient's specific symptoms, risk factors, and clinical presentation, as swelling can result from various conditions including heart failure, kidney disease, liver disease, venous insufficiency, lymphatic disorders, or medication side effects. According to the American Society of Hematology 2018 guidelines, for patients at low (unlikely) VTE risk, using D-dimer as the initial test reduces the need for diagnostic imaging, while for patients at high (likely) VTE risk, imaging is warranted 1. It is also important to note that the entire lower extremity arterial circulation should be evaluated, with detailed visualization of below-the-knee and pedal arteries, especially in patients with diabetes and ulceration of the foot 1. The most recent and highest quality study 1 recommends compression therapy as a helpful initial treatment for venous leg ulcers, with a minimum pressure of 20 to 30 mm Hg, and pressures of 30 to 40 mm Hg for more severe disease.

From the Research

Diagnostic Workups for Edema in the Lower Extremities

The diagnostic workups for edema in the lower extremities involve a combination of physical examination, medical history, laboratory tests, and imaging studies. The following are some of the key diagnostic workups:

• Basic metabolic panel, liver function tests, thyroid function testing, brain natriuretic peptide levels, and a urine protein/creatinine ratio to evaluate the underlying cause of edema 2
• Validated decision rules, such as the Wells and STOP-Bang criteria, to guide decision-making regarding the possibility of venous thromboembolic disease and obstructive sleep apnea, respectively 2
• D-dimer test or compression ultrasonography to evaluate for deep venous thrombosis in patients with acute unilateral lower-extremity edema 2, 3
• Duplex ultrasonography with reflux to diagnose chronic venous insufficiency in patients with chronic bilateral lower-extremity edema 2
• Echocardiography to assess for heart failure in patients with pulmonary edema or elevated brain natriuretic peptide levels 2, 4
• Lymphoscintigraphy to diagnose lymphedema if the diagnosis is unclear 2
• Point-of-care ultrasound to facilitate the diagnosis of heart failure by assessing for B-lines, cardiac function, and inferior vena cava size 4

Laboratory Tests and Imaging Studies

Laboratory tests and imaging studies play a crucial role in the diagnostic workup of edema in the lower extremities. Some of the key laboratory tests and imaging studies include:

• Complete blood count, basic metabolic profile, liver function tests, troponin, brain natriuretic peptide, and a chest radiograph to evaluate for heart failure 4
• D-dimer test to evaluate for deep venous thrombosis 3
• Ultrasonography to evaluate for venous thromboembolic disease and obstructive sleep apnea 2, 3
• Echocardiography to assess for heart failure 2, 4
• Lymphoscintigraphy to diagnose lymphedema 2

Clinical Assessment and Gestalt

Clinical assessment and gestalt are also important in the diagnostic workup of edema in the lower extremities. The following are some of the key clinical assessment and gestalt:

• Categorizing the edema according to its duration, distribution, and accompanying symptoms to narrow the differential diagnosis 5
• Evaluating the patient's medical history, demographic, and clinical risk factors to guide decision-making regarding the possibility of venous thromboembolic disease and obstructive sleep apnea 3
• Combining clinical assessment and gestalt with laboratory tests and imaging studies to facilitate the diagnosis of heart failure and other underlying causes of edema 4