An acute assessment unit (AAU) (also often called acute admissions unit or acute medical assessment unit) is a short-stay department in some British, Australian and New Zealand hospitals that may be linked to the emergency department, but functions as a separate department. The AAU acts as a gateway between a patient's general practitioner, the emergency department, and the wards of the hospital. The AAU helps the emergency department produce a healthy turnaround for patients, helping with the four-hour waiting rule. An AAU is usually made up of several bays and has a small number of side-rooms and treatment rooms. They are fully equipped with emergency medical treatment facilities including defibrillators and resuscitation equipment.