Can a deep vein thrombosis (DVT) cause lower leg swelling?

Can a Blood Clot Cause Lower Leg Swelling?

Yes, deep vein thrombosis (DVT) commonly causes lower leg swelling, which is one of the classic clinical presentations of this condition. 1 DVT occurs when blood clots form in one or more deep veins, typically in the lower extremities, and swelling is a direct result of venous obstruction.

Clinical Presentation of DVT

DVT presents with several characteristic signs and symptoms:

• Unilateral leg swelling - The most common and recognizable symptom 1
• Pain in the affected limb
• Erythema (redness) and warmth
• Swelling that worsens throughout the day and improves with rest and elevation 1

It's important to note that approximately one-third of patients with DVT may be asymptomatic 1, making diagnosis challenging in some cases.

Pathophysiology of Swelling in DVT

The swelling associated with DVT occurs due to:

1. Venous obstruction - The blood clot blocks normal venous return, causing fluid to accumulate in the affected limb 2
2. Increased venous pressure - The blockage leads to increased hydrostatic pressure in the veins distal to the clot
3. Fluid extravasation - The increased pressure forces fluid from the intravascular space into the surrounding tissues

Diagnostic Approach

When a patient presents with lower leg swelling suspicious for DVT:

• Clinical assessment using pretest probability tools
• D-dimer testing - Particularly useful when DVT is "unlikely" based on clinical assessment 3
• Compression ultrasonography - The primary imaging modality for confirming DVT 2

The American College of Chest Physicians recommends proximal compression ultrasound (CUS) or whole-leg ultrasound as the initial test for suspected DVT rather than venography 2.

Special Considerations

Extent of Swelling

The pattern of swelling can provide clues about the location of the DVT:

• Calf swelling - Often indicates isolated distal DVT
• Entire leg swelling - May suggest more proximal (iliofemoral) DVT 2
• Swelling with flank, buttock, or back pain - Could indicate isolated iliac vein thrombosis 2

Long-term Complications

If left untreated, DVT can lead to:

• Post-thrombotic syndrome (PTS) - A chronic condition occurring in approximately 23-29% of patients with DVT, characterized by persistent swelling, pain, skin changes, and in severe cases, venous ulceration 2
• Venous claudication - Bursting leg pain during exercise 1
• Pulmonary embolism - A potentially fatal complication if the clot dislodges and travels to the lungs 4

Conclusion

Lower leg swelling is a cardinal sign of DVT and should prompt appropriate diagnostic evaluation, especially when unilateral and accompanied by other symptoms like pain and warmth. Early diagnosis and treatment are essential to prevent serious complications such as pulmonary embolism and post-thrombotic syndrome.