Hydrops and Periodic edema

Hydrops noun - Swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities.

Periodic edema and hydrops are semantically related. In some cases you can replace phrase "Periodic edema" with "Hydrops", this terms are similar.

Periodic edema noun - Recurrent large circumscribed areas of subcutaneous edema; onset is sudden and it disappears within 24 hours; seen mainly in young women, often as an allergic reaction to food or drugs.

Hydrops and periodic edema are semantically related. You can use "Hydrops" instead a noun phrase "Periodic edema".