Welcome to Healthcare magic!
The information you have provided is inadequate.
He had constipation
for about 20 days.
The loose stools that followed can be due to overflow fecal incontinence
It may also be due to the laxative duphalac
he had taken.
if the bowel habits are normal , he can stop duphalac now.
Itching in anus can occur due to may causes like worm infestation, frequent loose stools, excessive sweating
in that area or yeast infection.
Does that answer your question?