Should a patient with overt lower extremity cellulitis also be evaluated for Deep Vein Thrombosis (DVT) if they present with a red, swollen leg?

From the Guidelines

Yes, a patient with overt leg cellulitis should be evaluated for deep vein thrombosis (DVT) if they present with a red, swollen leg, especially when risk factors for DVT are present or the clinical presentation is atypical for cellulitis alone. The evaluation typically involves a Wells score assessment followed by D-dimer testing and/or ultrasound imaging, as suggested by the American College of Chest Physicians evidence-based clinical practice guidelines 1. These conditions can coexist or mimic each other, making differential diagnosis challenging. Cellulitis is a bacterial skin infection causing erythema, warmth, and swelling, while DVT is a blood clot in deep veins that can present similarly. Misdiagnosis risks serious complications - untreated DVT can lead to pulmonary embolism, while inappropriate anticoagulation for misdiagnosed cellulitis carries bleeding risks. Features suggesting DVT include unilateral leg swelling, calf pain, history of thrombosis, recent immobilization, malignancy, or a poor response to antibiotics. When both conditions are suspected, it's appropriate to treat the cellulitis with antibiotics while simultaneously investigating for DVT, rather than assuming all symptoms are explained by the infection alone. According to the guidelines on the diagnosis and management of acute pulmonary embolism by the European Society of Cardiology, a negative D-dimer result in a highly sensitive assay safely excludes PE in patients with a low or moderate clinical probability 1. Additionally, compression ultrasonography has a sensitivity over 90% for proximal DVT and a specificity of about 95% 1, and can be used to diagnose DVT in patients with suspected PE. The most recent and highest quality study on the topic, the ACR Appropriateness Criteria for suspected lower extremity deep vein thrombosis, recommends the use of ultrasound duplex Doppler as the preferred imaging modality for diagnosing proximal DVT 1. Therefore, ultrasound imaging should be used to evaluate for DVT in patients with overt leg cellulitis and suspected DVT, as it is a non-invasive and reliable method for diagnosing proximal DVT. Some key points to consider when evaluating for DVT in patients with cellulitis include:

• The clinical presentation of cellulitis and DVT can be similar, making differential diagnosis challenging
• Risk factors for DVT, such as recent immobilization or malignancy, should be considered when evaluating for DVT
• A negative D-dimer result can safely exclude PE in patients with a low or moderate clinical probability
• Compression ultrasonography has a high sensitivity and specificity for diagnosing proximal DVT
• Ultrasound imaging should be used to evaluate for DVT in patients with overt leg cellulitis and suspected DVT.

From the Research

Diagnosis and Management of Cellulitis and DVT

• Cellulitis is a bacterial skin and soft tissue infection that can be mistaken for other conditions such as deep vein thrombosis (DVT), venous insufficiency, eczema, and gout 2.
• The presentation of unilateral limb swelling, erythema, and pain in patients with cellulitis and erysipelas can make it difficult to differentiate from DVT 3.
• A systematic review and meta-analysis found that the overall pooled incidence rate of DVT in patients with cellulitis or erysipelas was 2.1% for proximal DVT and 3.1% for any DVT 3.

Risk of DVT in Cellulitis Patients

• The risk of DVT in patients with cellulitis is low compared to the average risk of patients referred for compression ultrasound (CUS) and comparable to low-risk patients as determined by the Wells criteria 3.
• However, the Wells score may not be sufficient to rule out DVT or influence management decisions in the inpatient setting, with a higher failure rate and lower efficiency compared to the outpatient setting 4.

Clinical Considerations

• Patients with cellulitis and a red, swollen leg should be evaluated for DVT, especially if they have risk factors such as recent trauma, surgery, or immobility 3, 4.
• Compression ultrasound (CUS) may be useful in evaluating patients with suspected DVT, but the decision to use CUS should be based on individual patient risk factors and clinical presentation 3, 4.
• It is essential to consider the differential diagnoses of red legs, including chronic dermatological and venous disease, and to avoid misdiagnosis and unnecessary antibiotic therapy 5.