PO challenge is my favorite, BO challenge is my least favorite

You know what my favorite test in medicine is?
No.
No.
No. Stop saying stool tests, this is a rare instance when it is not directly related to poo.  It's the PO challenge.  "PO" means, "per oral", or, "by mouth".  So the challenge is, can this person take food and drink by mouth, i.e. give them food and see how they do. 

This is awesome.  I wish someone would PO challenge me daily.  Just run up to me in the street and yell, "PO challenge!" then put a cheese steak and a bag of peanut M&Ms in front of me.

"What? Oh, you fucker!  Ok, let's do this.  Sorry Grandma, drive yourself to rehab, I've got a PO challenge to crush!"