She was expected to stay for a couple days but spent just 24 hours at King Edward VII's Hospital after being admitted on yesterday afternoon.
The British monarch, dressed in a red coat, appeared relaxed and smiled as she walked to her waiting Bentley outside the hospital in central London. She is now likely to spend time convalescing at Windsor Castle.
Her next public outing is scheduled to be next Monday, when the Queen will carry out a day of Commonwealth-related engagements, including a service at Westminster Abbey where she will address a 2,000-strong congregation.
In keeping with her stiff upper lip approach to life, the 86-year-old had insisted the rest of the royal family carry on with their official duties while she was in hospital ? her first visit in nearly a decade.
She did not wish to "inconvenience" staff at the hospital by having to make arrangements for royal visitors and wanted to keep her hospital stay "as low key as possible".
Buckingham Palace had said the Queen had been admitted as a precaution and was otherwise in "good health and good spirits".
All official engagements for this week, including the Queen's trip to Rome, have either been cancelled or postponed.
News of her illness first emerged on Friday night when she cancelled a trip to Swansea on Saturday to mark St David's Day in a military ceremony. She was taken to the hospital from Windsor Castle, using a private car rather than an ambulance, and walked to and from the car without help.
According to royal sources, the Prince of Wales and the Duchess of Cornwall, who spent the weekend in Wales, and the Duke and Duchess of Cambridge and Prince Harry, who were in Switzerland at the weekend for a friend's wedding, are being kept updated on her health.
The Queen, who turns 87 next month, was last admitted to hospital in December 2003 for a scheduled operation on her knee. Her treatment, which has not been disclosed, was expected to include rehydration and tests to establish if the illness has been caused by an infection or an underlying problem.
London: Britain's Queen Elizabeth II was on Monday discharged from a hospital here after being treated for symptoms of gastroenteritis.
First Published: Monday, March 04, 2013, 22:59