You know how it goes, the new guy gets the worst jobs. Wiping ass is probably going to be the worst one around.

Part of the training Corpsmen have to go throug is a two week stint in the local Veteran's Hospital, usually in the long term care wards.
Of course, no one who can take care of themselves is going to be in the long term care ward.
So, new corpsmen often must clean up after their patients that can not perform basic care tasks for themselves.

This usually involves wiping copious amounts of ass.