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Fluid in Anterior or Posterior Cul-de-Sac: What It Means

Key Takeaways

Fluid in the cul-de-sac can indicate issues like endometriosis, an ectopic pregnancy, or pelvic inflammatory disease. A transvaginal ultrasound can detect fluid buildup in the cul-de-sac area. If the fluid contains pus or blood, it may need to be drained, and antibiotics could be needed to treat infection.

If you've had an ultrasound, you may have learned that there's fluid in your cul-de-sac area, which is behind the vagina. A small amount of clear fluid in the cul-de-sac is normal, but pus, blood, and/or pain can indicate a problem that requires medical attention. These conditions include (but are not limited to) endometriosis, an ectopic pregnancy, and pelvic inflammatory disease.

The anterior cul-de-sac is a pouch that sits between the bladder and the uterus. The posterior cul-de-sac sits between the uterus and the rectum. This latter cul-de-sac is also known as the pouch of Douglas, named for the Scottish physician James Douglas.

Causes

Abnormal fluid can fill the cul-de-sac, specifically the posterior cul-de-sac (also called the pouch of Douglas or rectouterine pouch) for many reasons. Sometimes a ruptured ovarian cyst or follicle leaks fluid. Sometimes there's a more severe problem. These are some possible causes:

• Ectopic pregnancy, where a pregnancy grows in a fallopian tube instead of the uterus
• Endometriosis, which occurs when the type of tissue that normally lines the uterus grows somewhere else
• Following culdocentesis, a procedure to remove fluid from the pouch
• Gross ascites, which is fluid buildup in your abdomen
• Hydatidiform mole, also known as a molar pregnancy, where a cyst forms from a fertilized egg
• High doses of estrogen that cause fluid to leak out of blood vessels
• Ovarian torsion, where the fallopian tube and ovary twist
• Pelvic abscess or hematoma, a pocket of infected fluid or blood
• Pelvic inflammatory disease
• Retrograde menstruation, which happens when your period flows back into your pelvis
• Tubo-ovarian abscess, a pus-filled area in your ovary and fallopian tube
• Uterine fibroids, growths in the uterus that are not cancerous
• A tear or break in the uterine wall

Fertility Treatment

If you are having fertility treatment, fluid in the cul-de-sac can be a symptom of ovarian hyperstimulation syndrome (OHSS)—a condition where high doses of fertility hormones make your ovaries swell.

If your healthcare provider suspects you have OHSS, they may suggest an ultrasound to check for fluid. During the ultrasound, they can measure your ovaries.

Usually, fluid in the cul-de-sac is not a cause for alarm. In some cases, though, it can cause discomfort or affect your fertility.

Diagnosis

Fluid in the cul-de-sac is diagnosed by doing a transvaginal ultrasound. A culdocentesis may also be done.

Transvaginal Ultrasound

A transvaginal ultrasound will show whether there is fluid behind the uterus. A wand is placed into the vagina to take more detailed ultrasound images. If fluid is found and you are having pain, you may need more tests.

Culdocentesis

Before transvaginal ultrasound became widely available, this procedure was used to check for fluid in this area. Now, it is mostly used to remove a fluid sample for testing.

In a culdocentesis, a needle is inserted through the vaginal wall to draw a sample of fluid. A numbing agent or anesthesia is often used. Your healthcare provider will use an instrument to hold your cervix in place so the needle enters in the right spot.

A small amount of fluid in the cul-de-sac is normal. But if the sample shows signs of pus or blood, the area may need to be drained.

Blood in the fluid could mean a cyst has ruptured or there is a tear. It could also be a sign of an ectopic pregnancy. Pus could mean you have an infection.

How Is Fluid Removed?

Fluid is removed for testing with a very thin needle that is inserted through the wall of the vagina. If the test is abnormal, culdocentesis will be done to remove the fluid. If there is pus in the fluid, your healthcare provider may prescribe antibiotics for the infection.