When you have an appendectomy in emergency, do they put in a catheter?

Sometimes: Reasons for placing a urinary catheter into the bladder include: monitoring a critically ill patient's urine output, relieving a temporary dysfunction of the bladder after surgery, and/or decompressing the bladder to prevent injury during surgery. None of these scenarios are common with appendicitis, but each can occur.

Pretty rarely: When someone has appendicitis and need surgery, they will be asked if they can empty their bladder on their own. If yes, no catheter will usually be needed.