This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Female & male reproductive system, rectum and anal canal, Subject name: Anatomy
While performing culdocentesis in female patient ,needle should be most efficiently inseed through which of the following structures ? 
Select and explain. 
A. Anterior fornix of the vagina, B. Posterior fornix of the vagina, C. Anterior wall of the rectum, D. Posterior wall of the uterine body
B: Posterior fornix of the vagina
Answer: B: Posterior fornix of the vagina 
Explanation: A needle should be inseed through the posterior fornix, just below the posterior lip of cervix while the patient is in supine position, to aspirate abnormal fluid i the cul-de-sac of Douglas(rectouterine pouch). Rectouterine excavation is not most efficiently aspirated by puncture of other structures.