The Scottish captain has undergone surgery in an effort cure the recurring problem, although his club insist the latest procedure was planned as part of his long-term recovery.
United have released a statement confirming a further lengthy absence for the 28-year-old and explained the decision was taken at the "optimal time" as a consequence of "a period of sustained good health."
" Darren Fletcher will be unavailable for the remainder of this season having undergone surgery to resolve his ulcerative colitis condition," read the statement.
"This was a planned procedure undertaken at the optimal time having achieved a period of sustained good general health, as illustrated by the fact that Darren has trained with the team regularly this season and been available for selection right up to the operation."
He then returned to international football, featuring for Scotland in their 2-1 defeat by Wales in Cardiff.
Fletcher's last start for United was on December 1 in their 4-3 win at Reading. Since then he has made only two brief substitute appearances, his last on St Stephen's Day against Newcastle. (© Daily Telegraph, London)