Differential Diagnosis for Unilateral Swelling in the Calf and Foot

Single Most Likely Diagnosis

• Deep Vein Thrombosis (DVT): This is the most likely diagnosis due to the unilateral nature of the swelling, which is a common presentation of DVT. The calf and foot are typical locations for DVT to occur, and it can lead to significant swelling due to the obstruction of blood flow.

Other Likely Diagnoses

• Cellulitis: A bacterial infection of the skin and subcutaneous tissues that can cause unilateral swelling, redness, and warmth in the affected area. The calf and foot are common sites for cellulitis, especially in individuals with compromised skin integrity or those who have recently experienced trauma to the area.
• Lymphedema: Although typically bilateral, lymphedema can present unilaterally, especially if there is a history of surgery, radiation, or infection affecting the lymph nodes. It causes swelling due to the accumulation of lymph fluid.
• Muscle Strain or Tear: Direct injury to the muscles in the calf can lead to swelling, pain, and limited mobility. This is more likely if there is a history of recent physical activity or trauma.

Do Not Miss Diagnoses

• Compartment Syndrome: A medical emergency characterized by increased pressure within a muscle compartment, leading to nerve and muscle damage. It presents with the 5 Ps: pain, pallor, pulselessness, paresthesia, and poikilothermia. Although less common, missing this diagnosis can result in severe and permanent damage.
• Phlegmasia Cerulea Dolens: A severe form of DVT that causes significant swelling and cyanosis of the affected limb. It is a medical emergency due to the high risk of limb loss and pulmonary embolism.
• Necrotizing Fasciitis: A severe infection of the fascia and subcutaneous tissues that can rapidly progress and is life-threatening. It may present with severe pain, swelling, and skin changes.

Rare Diagnoses

• Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and pain. It is more common in women and can be mistaken for lymphedema.
• Erythromelalgia: A disorder that causes burning pain, heat, and redness in the hands and feet, and can also lead to swelling. It is relatively rare and can be primary or secondary to other conditions like myeloproliferative disorders.
• Klippel-Trenaunay Syndrome: A rare congenital condition characterized by vascular malformations, leading to swelling, varicose veins, and skin changes in the affected limb.