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Culdocentesis is a clinical procedure used to identify abnormalities in the female pelvis. During the procedure, a plunger syringe is used to collect fluid from the recto-uterine pouch, a space located just behind the uterus in the lower abdomen. Based on the contents and quantity of the fluid sample retrieved, a doctor may be able to determine the presence of pelvic inflammatory disease (PID), an ovarian cyst, an ectopic pregnancy, or another type of complication. A licensed gynecologist, obstetrician, or emergency medical doctor can usually perform the outpatient procedure in a matter of minutes.
The recto-uterine pouch, also called the cul-de-sac and the pouch of Douglas, is situated behind the vagina and above the rectum. It is the lowest part of a woman's empty abdominal cavity. If there is a cyst, bacterial lesion, or another abnormality in the pelvis, fluid can escape and pool up in the pouch. Rarely, an ectopic pregnancy can occur when a fertilized egg embeds outside of the uterus adjacent to the pouch, leading to amniotic fluid buildup. Culdocentesis is an effective test to determine whether or not such problems exist.
Patients are usually given sedatives before undergoing culdocentesis to make them more comfortable. A localized anesthetic is also injected into the vagina to limit pain. To begin the procedure, the gynecologist uses a speculum to separate the vaginal walls for easier access. A syringe is then used to puncture the back of the vagina. The doctor is careful when choosing a puncture spot to avoid accidentally damaging the small intestine, rectum, or kidneys.
The plunger syringe is used to retrieve fluid — if it is in fact present. A dry sample usually indicates that no major complication exists, though the doctor may decide to repeat the procedure to make sure that he or she did not miss the fluid pool on the first try. If fluid is collected, it is sent to a laboratory for analysis. A large amount of clear liquid may indicate an ovarian cyst, while pus and thick yellow liquid are signs of bacterial infection. Amniotic fluid and dark, thin blood are typical findings with ectopic pregnancy.
Due to advancements in diagnostic imaging technology, culdocentesis is not often performed in modern hospitals and gynecology clinics. Ultrasound machines can usually detect fluid buildups in the recto-uterine pouch with greater accuracy than culdocentesis procedures. In addition, ultrasounds are not invasive and carry almost no risk to a patients' health. Culdocentesis is still popular in areas of the world where there is limited access to diagnostic imaging equipment. The procedure is sometimes preferred in emergency situations, such as suspected ruptures of ectopic pregnancies in the recto-uterine pouch, in which it would take too long to set up, administer, and interpret ultrasounds.