Swollen Calf
Such has been the publicity about ‘economy class syndrome’ that this presentation – and the closely related symptom, ‘calf pain’ (refer to that section) – has become quite common. The worry the patient has about a possible DVT can prove quite ‘infectious’, with the GP anxious not to miss this significant problem. In most cases, a careful history, backed up by appropriate examination, should reveal the true cause.
Differential diagnosis
Common Diagnoses
- Cellulitis
- Most Causes of Swollen Ankles
- Muscle Strain/Rupture (Especially Rupture of Plantaris Tendon)
- Ruptured Baker’s Cyst
- DVT
Occasional Diagnoses
- Ruptured Achilles Tendon
- Varicose Eczema
- Phlebitis
Rare Diagnoses
- Muscle Herniation Through Fascia (Especially Tibialis Anterior)
- Muscular Neoplasm
- Pseudohypertrophy (as in Muscular Dystrophy)
Ready reckoner
Key distinguishing features of the most common diagnoses
| Cellulitis | Swollen Ankles | Muscular | Baker’s Cyst | DVT | |
|---|---|---|---|---|---|
| Fever | Yes | No | No | No | Possible |
| Bilateral | Possible | Possible | No | No | Possible |
| Sudden Pain | No | No | Yes | Possible | Possible |
| Previous Swelling Behind Knee | No | No | No | Yes | No |
| Skin Red | Yes | Possible | No | No | Possible |
Possible investigations
Likely: None (unless sent to hospital).
Possible: FBC, ESR/CRP and other investigations for swollen ankles (see also 'swollen ankles' section); usually in hospital – D-dimer, ultrasound, venography.
Small Print: None.
- FBC, ESR/CRP: Elevated white cell count and ESR/CRP in cellulitis.
- D-dimer: Raised level suggests DVT but is not conclusive.
- Ultrasound: May help diagnose DVT and useful in confirming ruptured Baker’s cyst as the cause. Venography necessary to confirm DVT in some cases.
Top Tips
- The swelling resulting from a muscle rupture can be impressive – but a typical history with pain (described as ‘like being shot in the calf ’) preceding the swelling should clinch the correct diagnosis.
- Varicose eczema is often misdiagnosed as cellulitis. Clues are that it is commonly bilateral, itches more than hurts and is not accompanied by fever. To complicate matters, varicose eczema can become infected, causing cellulitis.
- Anxiety about possible DVT may cloud the presentation – careful questioning may reveal that swelling is, in fact, long-standing and/or bilateral, making DVT very unlikely.
Red Flags
- Patients with unexplained DVT are three to four times more likely than controls to have an underlying malignancy – so, once the DVT has been dealt with, consider appropriate investigation.
- In high-risk patients – such as those who have just returned from a long haul flight – your index of suspicion for DVT should be raised.
- When the history suggests muscular rupture, ensure that the Achilles tendon is intact.