This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
True statement about pelvic abscess is 
Select and explain. 
A. Uncommon cause of intra peritoneal abscess, B. Associated with pyothorax, C. May spontaneously drain via rectum, D. Identified by CT if there is full bladder
C: May spontaneously drain via rectum
Answer: C: May spontaneously drain via rectum 
Explanation: Pelvic abscess :

It is common cause intraperitoneal abscess.
It is easily identified by CT if the bladder is empty.