Pope in hospital: why has Francis had surgery and what is the prognosis?

Members of the media report from outside of the Gemelli Polyclinic, where Pope Francis is being treated (Riccardo De Luca/AP)

Pope Francis has had surgery to remove part of his left colon in what the Vatican has described as a planned procedure.

Doctors say the bowel problems that the 84-year-old pope was experiencing are very common in older people, although only about 10% to 20% of people with similar problems require surgery.