Welcome to Healthcaremagic,
Since you had surgery in rectum
, it may be cause for your Paste like stools.
In rectum, and large intestine, water is absorbed from the stool. This makes stool hard and putty consistency.
Your stool consistency will change in one week or soon.
If the stool consistency is not changed, consult an Gastroenterologist.
Check Stool for Ova or cyst
So do not get worried.
Avoid heavy food for some days.
Hope this helps.