Picture of Pitting Edema
Pitting edema is a form of tissue swelling that occurs due to fluid accumulation. An underlying disorder involving the heart, liver, or kidneys may be responsible for the condition. Salt accumulates in tissues and attracts water, leading to the swelling. If a finger is pressed into and then removed from the area, it will leave a pit, hence the name pitting edema. Constricting clothing or elastic socks may also leave marks on the skin.
Text Reference: American Family Physician: "Edema: Diagnosis and Management"