Published Wednesday, 18 December 2013
It follows what the trust described as a "critical shortage" of medical staff.
The review will look at the future of A&E care in both hospitals and will consider a "range of options", including reducing opening hours.
A decision is expected to be made this week.
In a statement, the trust said: "The South Eastern Trust is experiencing a critical shortage of medical staff in both the Downe and Lagan Valley Emergency Departments.
"This has been a critical position for a number of months and there is little prospect of a resolution. In fact, the situation has deteriorated over recent weeks.
"The Trust will be reviewing a range of options for continued provision of Emergency Care services at both sites with the objective of maintaining both Emergency Departments, albeit with reduced opening hours. A decision is likely to be taken this week."
South Down MP Margaret Ritchie, who said she spoke to Health Minister Edwin Poots on Tuesday, has told UTV there must be "no dilution of services".
The SDLP politician added: "The trust are looking at proposals to possibly close the A&E at Downe Hospital and Lagan Valley at weekend or in the evening time.
"The bottom line is there must be no dilution of services and no closures because we cannot be sending people to the Ulster Hospital in Dundonald, as it's already overloaded."
In a statement, the Health Department said the trust is working to address the situation but added that smaller hospitals are often more vulnerable to staff shortages.
A spokesperson went on: "The difficulty being experienced by the Trust reflects difficulties being experienced in many emergency departments across the UK to maintain the required level of medical staff.
"Services provided at smaller hospitals, which are dependent on small teams to sustain services, are more vulnerable to shortages in staff.
"Occasionally, situations will arise when the service experiences difficulty in providing the necessary clinical support to sustain the service."
© UTV News