Final answer:
The cause of edema is impaired lymphatic drainage, along with various other factors such as blood vessel damage and decreased osmotic pressure due to a lack of plasma proteins like albumin produced by the liver.
Step-by-step explanation:
The cause of edema is B. Impaired lymphatic drainage. However, there are also other important contributing factors. Edema is an accumulation of excess fluid in the tissues, which can occur due to various conditions such as water leakage from blood capillaries. This can be influenced by several physiological reasons, including damage to blood vessels, impaired lymphatic drainage which disrupts the normal fluid absorption, or due to decrease in osmotic pressure that may occur in chronic and severe liver disease. When the liver is unable to manufacture plasma proteins, it leads to a decrease in colloid osmotic pressure, which is essential for counterbalancing the hydrostatic pressure in the capillaries, ultimately resulting in water loss from the blood to the surrounding tissues and causing edema. One significant plasma protein involved in regulating water content in the tissues is albumin, and a deficiency of albumin leads to edema.