What causes swelling in the lower limbs?

Lower limb edema, also known as lower limb swelling, is a symptom caused by excessive accumulation of fluid in the body's tissue spaces. The possible causes are diverse and can be mainly categorized into the following groups:

1. Physiological factors: Such as hormonal changes during a woman's menstrual cycle or uterine enlargement during pregnancy compressing the inferior vena cava, prolonged standing or sitting, or working for extended periods in high-temperature environments. Bilateral lower limb edema may occur, but it typically resolves spontaneously.

2. Cardiovascular diseases: For example, heart failure—especially right-sided heart failure—can impede venous return, causing lower limb edema.

3. Kidney diseases: In cases of renal insufficiency or nephrotic syndrome, the kidneys cannot effectively remove excess water and salt from the body, leading to sodium and water retention and resulting in edema.

4. Liver diseases: Conditions such as cirrhosis can lead to hypoalbuminemia, which reduces the colloid osmotic pressure of blood, causing fluid to leak into the tissue spaces and trigger edema.

5. Lymphatic system disorders: Obstruction of lymphatic vessels or impaired lymphatic drainage following lymph node removal can lead to localized or generalized edema. This is commonly seen as upper limb lymphedema after breast cancer surgery.