The Eloessar flap is a surgical procedure developed by Dr. Leo Eloesser in 1935 at the San Francisco General Hospital. It was originally intended to aide with drainage of tuberculous empyemas, since at the time there were no effective medications to treat tuberculosis. The procedure was used extensively until the development of effective chemotherapy for tuberculosis in the late 1940s and early 1950s. It is still used occasionally for chronic empyemas.