What is the diagnosis and management for a patient with a purple, blanchable, half-dollar-size area on the medial calf with induration and surrounding lower extremity (BLE) edema?

Diagnosis: Superficial Thrombophlebitis (SVT)

This presentation of a purple, blanchable, half-dollar-size area on the medial calf with induration and bilateral lower extremity edema is most consistent with superficial thrombophlebitis (SVT), though deep vein thrombosis (DVT) must be urgently excluded given the overlapping clinical features and potential for concurrent disease. 1

Critical First Step: Exclude DVT

Proceed immediately to venous duplex ultrasound to rule out DVT before finalizing the diagnosis of isolated SVT. 2, 3 The key reasons are:

• SVT and DVT can occur simultaneously, and each predisposes to the other condition 1
• Extensive SVT in the saphenous vein can progress to involve the deep venous system at the saphenofemoral junction and precipitate pulmonary embolism 1
• The bilateral lower extremity edema raises concern for possible deep venous involvement or systemic causes 2
• Approximately one-third of DVT patients are completely asymptomatic, so absence of classic DVT signs does not exclude the diagnosis 3

Diagnostic Reasoning

Why This is Likely SVT:

• Blanchability: The purple discoloration that blanches suggests superficial vascular involvement rather than deep venous thrombosis 1
• Localized induration: SVT characteristically presents with tenderness, erythema, and/or an indurated cord associated with a superficial vein 1
• Size and location: A half-dollar-size area on the medial calf corresponds to the typical distribution of the greater saphenous vein, where most lower extremity SVTs occur 1

Why DVT Must Still Be Excluded:

• The bilateral lower extremity edema is atypical for isolated SVT, which is usually more localized 2
• SVT is more likely than DVT to be symptomatic with pain, tenderness, and erythema, but the presence of bilateral edema suggests possible deep system involvement 1

Ultrasound Protocol

Order complete duplex ultrasound with the following specifications: 2, 3

• Evaluate the location and extent of superficial thrombosis
• Assess for proximal deep vein involvement, particularly at the saphenofemoral junction
• Include compression views of the common femoral and popliteal veins
• Evaluate calf veins (posterior tibial and peroneal) given the calf location of symptoms 2

Management Based on Ultrasound Results

If Ultrasound Shows Isolated SVT (No DVT):

Treatment depends on the location and extent of SVT: 1

• Extensive SVT near saphenofemoral junction: Consider anticoagulation to prevent extension into deep system 1
• Limited peripheral SVT: Conservative management with NSAIDs, warm compresses, and compression therapy 4, 5
• Follow-up imaging: Progression of symptoms should be accompanied by repeat ultrasound 1

If Ultrasound Shows DVT:

Initiate therapeutic anticoagulation immediately without confirmatory venography 1, 2, 3, 6

• Proximal DVT carries 50-60% risk of pulmonary embolism with 25-30% mortality if untreated 2
• Even isolated distal (calf) DVT warrants anticoagulation in patients with severe symptoms 2
• Approximately 15% of untreated symptomatic distal DVT extends into proximal veins 2

Addressing the Bilateral Lower Extremity Edema

The bilateral edema component requires separate evaluation: 2, 5

• Obtain basic metabolic panel, liver function tests, brain natriuretic peptide, and urine protein/creatinine ratio 5
• Review medications for causes of edema (antihypertensives, anti-inflammatory drugs, hormones) 5
• Consider chronic venous insufficiency, which commonly causes dependent edema and hemosiderin deposition 4, 5
• Evaluate for heart failure, hypoproteinemia, or obstructive sleep apnea as systemic causes 2, 7

Critical Pitfalls to Avoid

• Do not dismiss this as simple cellulitis without ultrasound evaluation, as both SVT and DVT can present with erythema, warmth, and swelling 1, 2
• Do not rely on D-dimer testing if clinical suspicion for DVT is moderate to high; proceed directly to ultrasound 1, 2
• Do not accept limited proximal-only ultrasound given the calf location of symptoms; complete evaluation including calf veins is necessary 2, 3
• Do not use diuretics empirically for the bilateral edema until the etiology is determined, as inappropriate diuretic use may induce chronicity 8

Compression Therapy Considerations

Once DVT is excluded, compression therapy is appropriate for both SVT and chronic venous edema: 1, 5

• Minimum pressure of 20-30 mm Hg for chronic venous disease 2
• 30-40 mm Hg for more severe disease 2
• Multilayered compression bandaging may be effective for refractory peripheral edema 8