Differentials
Cellulitis
SIGNS / SYMPTOMS
Patients with cellulitis usually present with redness, heat, and swelling in the dermis of the affected leg. The affected area is likely to be smaller than in DVT (which may involve the entire foot, calf, or thigh), but the signs more pronounced.
The demarcation of the skin margins affected by cellulitis is more defined than in DVT.
Portal of infection entry may be identified.[97]
Fever and prior history of cellulitis is common.
May occur with a concurrent DVT.
INVESTIGATIONS
Leukocytosis is common, with a WBC count >10 × 10⁹/L (10,000 cells/microlitre).
Fluid collection seen if abscess present.
Ultrasound differentiates diagnoses.
Calf muscle tear/Achilles' tendon tear
SIGNS / SYMPTOMS
History of trauma or sudden onset of calf pain.
Muscle tear is difficult to differentiate from DVT on examination. Although defect or spasm of calf muscles is noted on examination, calf DVT may occasionally be associated with spasm.
INVESTIGATIONS
No DVT seen on MRI or ultrasound.
Oedema associated with muscle tear makes it very difficult to visualise the calf veins using ultrasonography. Furthermore, extreme tenderness associated with a muscle tear makes it difficult to compress with the ultrasound probe.
Calf muscle haematoma
SIGNS / SYMPTOMS
Calf injury or sudden onset of calf pain. There may be ecchymosis on the skin.
Calf haematoma, calf muscle tear, and calf muscle tendon tear frequently occur in the absence of injury or trauma.
INVESTIGATIONS
Venous ultrasound shows no thrombosis, and there may be ultrasound evidence of a haematoma.
Large or ruptured popliteal cyst (Baker's cyst)
SIGNS / SYMPTOMS
Sudden onset of calf pain.
Tenderness in popliteal fossa.
INVESTIGATIONS
Ultrasound shows fluid in the soft tissues of the calf or visualises cyst.
Pelvic/thigh mass/tumour compressing venous outflow from the leg
SIGNS / SYMPTOMS
Oedema usually occurs without pain in venous outlet obstruction.
Difficult to distinguish from iliac or caval DVT (which may co-exist).
INVESTIGATIONS
Venous ultrasound, CT scan, or MRI of abdomen, pelvis, and thigh with contrast, may show obstructing mass impinging on the femoral, iliac, or vena cava vessels.
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