What could cause both feet to swell up while sitting down?

Several factors can contribute to swelling in both feet while sitting down. Here are some possible causes:

1. Gravity: Sitting down for extended periods can cause fluid to accumulate in the feet due to gravity. When you are standing, your muscles help pump fluid back towards the heart, but when you are seated, this process can be less efficient, leading to fluid retention and swelling.

2. Tight Shoes: Wearing tight shoes or socks that restrict circulation can worsen swelling in the feet. Tight footwear can compress the blood vessels and impair blood flow, which can lead to fluid buildup and swelling.

3. Medical Conditions: Certain medical conditions can also cause bilateral foot swelling. Some examples include:

- Heart Failure: Congestive heart failure can cause fluid retention and swelling in the lower extremities, including the feet.

- Kidney Disease: Kidney problems can affect the body's ability to regulate fluid balance, leading to edema (swelling) in various body parts, including the feet.

- Liver Disease: Liver conditions, such as cirrhosis, can cause fluid retention and swelling in the extremities.

- Blood Clots: Deep vein thrombosis (DVT), a condition in which blood clots form in the deep veins of the legs, can cause swelling and pain in the affected leg, including the foot.

4. Pregnancy: Pregnant women often experience swelling in the feet and ankles due to hormonal changes and increased fluid volume.

5. Lymphatic System Issues: Problems with the lymphatic system, such as lymphedema, can lead to fluid buildup and swelling in the feet and legs.

If you experience persistent or severe swelling in both feet, especially if accompanied by other symptoms such as shortness of breath, chest pain, or sudden onset, it is recommended to consult a healthcare professional for proper evaluation and diagnosis.