Idiopathic Edema: This condition is common in young women and is characterized by intermittent swelling of the legs, hands, and face without an identifiable cause. It is often related to hormonal changes and can be exacerbated by standing, heat, and premenstrual fluid retention.

Venous Insufficiency: This condition occurs when the veins have problems returning blood from the legs back to the heart due to issues like valve problems or obstruction. It can lead to swelling, especially after standing for long periods.
Lymphedema: Although less common in young individuals without a history of surgery or radiation, primary lymphedema can occur. It involves the abnormal collection of protein-rich fluid in the interstitial tissue due to a problem with the lymphatic system.
Hypothyroidism: Swelling can be a symptom of hypothyroidism, a condition where the thyroid gland doesn't produce enough thyroid hormone, which is crucial for various bodily functions including metabolism regulation.
Fluid Overload: Conditions leading to fluid overload, such as excessive sodium intake or early stages of heart failure, can cause bilateral leg swelling.

Deep Vein Thrombosis (DVT): A blood clot in the deep veins of the legs, which can be life-threatening if it breaks loose and travels to the lungs (pulmonary embolism). Risk factors include recent travel, surgery, pregnancy, or use of oral contraceptives.
Nephrotic Syndrome: A collection of symptoms indicating kidney damage, specifically to the glomeruli, leading to severe swelling (edema), particularly in the legs.
Heart Failure: Although less common in young individuals, heart failure can cause fluid buildup in the body, leading to swelling in the legs.
Pulmonary Hypertension: High blood pressure in the arteries that supply blood to the lungs, which can lead to right-sided heart failure and subsequent leg swelling.

Sarcoidosis: A disease characterized by the growth of tiny collections of inflammatory cells (granulomas) in any part of the body — most commonly the lungs and lymph nodes — but can also affect other areas, potentially leading to swelling.
Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and pain.
Fabry Disease: A rare genetic disorder that results from the buildup of a particular type of fat in the body's cells, affecting many parts of the body and potentially causing swelling among other symptoms.

Complete Medical History: Including questions about recent travel, surgery, medication use (especially oral contraceptives), and family history of clotting disorders or other conditions.
Physical Examination: Looking for signs of DVT (warmth, redness, tenderness), heart failure (jugular venous distension, lung crackles), and other systemic signs.
Laboratory Tests:
- D-dimer: To help diagnose or rule out DVT or pulmonary embolism.
- Complete Blood Count (CBC): To check for signs of infection or blood disorders.
- Electrolyte Panel: To assess for signs of fluid overload or kidney dysfunction.
- Thyroid Function Tests: To evaluate for hypothyroidism.
- Urinalysis: To check for proteinuria, which could indicate nephrotic syndrome or other kidney issues.
Imaging Studies:
- Ultrasound of the Legs: To diagnose DVT.
- Chest X-ray: If heart failure or pulmonary hypertension is suspected.
- Echocardiogram: To assess heart function if heart failure is a concern.
Other Tests: Depending on the suspected underlying cause, other tests such as lymphoscintigraphy for lymphedema or a sleep study if sleep apnea is suspected as a contributor to fluid retention may be ordered.