"Yesterday"! What if that was you?
And it doesn't sound to me like an "intestinal blockage" since he's still defecating*, but it could be a tumor or a cyst, or other serious issue.
(*at least, not typical constipation nor a complete blockage)
In any case, I wouldn't ignore it as it's only likely to get worse. If your sink was stopped up, but a little water would still go down, would you wait to call a plumber until nothing went down the drain? Usually there's a better prognosis if you don't wait around.