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

First, a pelvic examination is done. Then, the cervix is grasped with an instrument and lifted slightly. A long, thin needle is inserted through the vaginal wall (just below the uterus). A sample is taken of any fluid found in the space, and the needle is then withdrawn.

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

There may be 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 pain occurs in the lower abdomen and pelvic regions, and other tests suggest that fluid may be present in the cul-de-sac. This test may be done when a ruptured ectopic pregnancy or ovarian cyst is suspected. The test is now performed infrequently because of the availability and effectiveness of ultrasound examinations to 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 other tests may be needed. If fluid is drawn, it is cultured to see if infection is present. If nonclotting blood is found in the cul-de-sac, emergency surgery may be required.

There is a slight risk of puncturing any mass, cyst, or ectopic pregnancy that exists. The needle should not be inserted too far or with such firmness that it penetrates the uterine wall.

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