Is it permissible for one in I'tikaf to leave for a doctor's appointment?

I'tikaf is the act of staying and secluding oneself in the mosque. It is a recommended Sunnah (definition), especially during the last ten days of Ramadan (definition), and it only becomes obligatory if one makes a vow (nadhr (definition)). The basic principle is that the one performing i'tikaf should not leave the mosque except for a need that cannot be fulfilled inside it, such as relieving oneself or performing ghusl (definition). If there is an urgent need to visit a doctor that cannot be postponed, there is no harm in leaving and then returning to the mosque.