Differential Diagnosis for Unilateral Swelling in a Man on Lasix 80mg Daily

Single Most Likely Diagnosis

• Dependent Edema: This is a common side effect of loop diuretics like Lasix (furosemide), especially at high doses. The mechanism involves the diuretic effect causing a decrease in blood volume, which can lead to decreased blood flow to the kidneys and an increase in the reabsorption of sodium and water in the proximal tubules, potentially causing edema in dependent areas due to gravity.

Other Likely Diagnoses

• Cellulitis or Skin Infection: Although DVT has been ruled out, infections can cause unilateral swelling and should be considered, especially if there are signs of redness, warmth, or purulent discharge.
• Lymphedema: This could be primary or secondary due to various causes, including surgery, infection, or trauma. It's a consideration in unilateral swelling, especially if the swelling is chronic.
• Venous Insufficiency: Even though DVT has been ruled out, chronic venous insufficiency could cause unilateral swelling, particularly if there's a history of DVT, varicose veins, or other venous disorders.

Do Not Miss Diagnoses

• Compartment Syndrome: Although less likely, compartment syndrome is a medical emergency that requires immediate attention. It could present with swelling, pain (especially on palpation), and decreased mobility of the affected limb.
• Nephrotic Syndrome: This condition, characterized by heavy proteinuria, hypoalbuminemia, and edema, could be a cause of unilateral swelling, especially if the patient has underlying kidney disease.
• Malignancy (e.g., Lymphoma or Soft Tissue Sarcoma): Although rare, malignancies can cause unilateral swelling due to mass effect or lymphatic obstruction.

Rare Diagnoses

• Fabry Disease: A genetic disorder that can lead to lymphedema and other systemic symptoms due to the accumulation of globotriaosylceramide.
• Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and pain.
• Factitious or Self-Induced Edema: Although uncommon, some patients might intentionally cause or exacerbate edema for various psychological reasons.

Each of these diagnoses should be considered in the context of the patient's full medical history, physical examination, and additional diagnostic tests as necessary.