A surprise operation in mid-January, a long and discreet convalescence and then a furore around an edited family photo released by Kensington Palace.

Here's what we know about the health and related woes of Catherine, Princess of Wales, whose husband Prince William is heir to the British throne.

  Operation 

 An announcement at 2:00 pm (1400 GMT) on January 17 by Kate and William's Kensington Palace office took royal watchers by surprise.

"The Princess of Wales was admitted to The London Clinic yesterday (January 16) for planned abdominal surgery," it disclosed.

The surgery had been successful, it added, and Kate was expected to remain in hospital for 10 to 14 days.

Based on medical advice at the time, the princess was "unlikely to return to public duties until after Easter" on March 31, the palace added.

The royal family has kept the reasons for the surgery confidential.

"She hopes that the public will understand her desire to maintain as much normality for her children as possible and her wish that her personal medical information remains private," the statement read.

The palace said later the health concern was not related to cancer.

  Convalescence 

 On January 29, the palace announced that Kate, 42, had been discharged from hospital and had "returned home to Windsor", west of London, "to continue her recovery from surgery".

All her forthcoming commitments were cancelled, including an official visit to Italy with William, the BAFTA film awards ceremony, the annual Commonwealth Day celebration, Saint David's Day on March 1 and Saint Patrick's Day on March 17.

On February 12, British media reported that the princess had left Windsor to spend a few days with William and their three children at Sandringham, eastern England.

  Questions 

 Unanswered questions about the nature of Kate's surgery and her lengthy disappearance from public view have fuelled speculation on social media.

Britain's tabloids, which are usually supportive of the princess, have also voiced concerns over the apparent lack of transparency around her health.

On February 8, when William attended his first public engagement since Kate's operation, he provided no information about his wife's health.

Instead, he expressed gratitude for the public's support after it was announced that his father, King Charles III, was being treated for cancer.

The mystery intensified on February 27 when William unexpectedly cancelled his attendance at a memorial ceremony for his late godfather, King Constantine II of Greece, due to a "personal matter".

Kensington Palace did not elaborate but said Kate "continues to be in good health".

On March 4, the first photo of the princess since her surgery was published in US celebrity news outlets.

She was seen wearing black sunglasses, seated in the passenger seat of a vehicle driven by her mother, Carole Middleton.

The following day, the British Army announced on its website that Kate would participate in June in the Trooping the Colour, the military parade to celebrate the king's official birthday.

Kensington Palace, though, did not confirm her attendance. The mention of her appearance was removed from the website that evening.

 Edited photo 

 In an apparent bid to dispel the rumours around her health, Kensington Palace distributed on Sunday an official photograph said to have been taken by William of his wife with their children.

However, questions quickly emerged about the Mother's Day portrait of a smiling Kate, casually dressed and seated in a garden chair, surrounded by George, Charlotte and Louis.

Inconsistencies included the zip of Kate's jacket being misaligned in one place, and the fact that part of Charlotte's sleeve is missing. The eight-year-old princess's hair also ends abruptly on her shoulder.

The discrepancies prompted AFP and other leading news agencies to withdraw the image, citing policies around the ethics of publishing edited images.

Kate then issued a statement saying: "Like many amateur photographers, I do occasionally experiment with editing". She apologised for "any confusion" caused.

But the episode, widely seen as a public relations disaster, has only heightened speculation about her current condition.