Culdocentesis is a procedure that checks for abnormal fluid in the space just behind the vagina (cul-de-sac).

First, you will have a pelvic examination. Then, the health care provider will grasp the cervix with an instrument and lift it slightly.

A long, thin needle is inserted through the wall of the vagina (just below the uterus). A sample is taken of any fluid found in the space. The needle is pulled out.

You may be asked to walk or sit for a short time before the test is done.

You may have an uncomfortable, cramping feeling when the cervix is grasped. There is a sharp, brief pain as the needle is inserted.

This procedure is done when you have pain in the lower abdomen and pelvis, and other tests suggest there is fluid in the cul-de-sac. This test may also be done when the doctor suspects a ruptured ectopic pregnancy or ovarian cyst.

The test is rarely done today because an ultrasound can usually detect fluid in the cul-de-sac.

No fluid in the cul-de-sac, or a very small amount of clear fluid, is normal.

Even when no fluid is found, it may be present, and you may need other tests. If fluid is drawn, it is cultured to see if you have an infection. If nonclotting blood is found in the cul-de-sac, you may need emergency surgery.

There is a slight risk of puncturing any growth, cyst, or ectopic pregnancy that exists. The needle should not be inserted too far or hard enough to go through the uterine wall.

You may need someone to take you home if you were given a sedative.