The problems affecting Charles Scicluna are not extremely serious, "but neither are we dealing with a very simple ailment", Catholic bishop's conference spokesman Jaime Coiro said.
The Maltese bishop began meeting victims and others opposed to the appointment of a bishop accused of covering up for the country's most notorious paedophile priest.
Mr Coiro said Pope Francis has called for interviews with witnesses to continue from Wednesday through to Friday as planned. A Spanish priest who is assisting Bishop Scicluna will take part.
Stay up to date with the latest news stories from a Christian perspective. Sign up to our daily newsletter and receive more stories like this straight to your inbox every morning.