Diet after having 90% of rectum removed

My brother is having a hard time in controlling his bowel movements since having 90% of his rectum removed.
He is easily constipated or with no warning he soils himself. He is frequently nervous about leaving home.
What sort of diet should he be on?

[Morecambe]

Try a high fibre diet if you have not already done so - but be prepared to discontinue it if there is no change or improvement.

regards
Morecambe