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.
Verywell / Jessica Olah
Sometimes aruptured ovarian cystor follicle leaks fluid.
Sometimes there’s a more severe problem.
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.
Aculdocentesismay also be done.
Transvaginal Ultrasound
Atransvaginal ultrasoundwill 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.
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.
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?
If there is pus in the fluid, your healthcare provider may prescribe antibiotics for the infection.
Summary
Two small pouches called cul-de-sacs are located on either side of the uterus.
Fluid sometimes builds up in these pouches, specifically the posterior pouch.
Infection, pregnancy complications, or health conditions such as endometriosis or fibroids could be the cause.
It’s also possible that a cyst, a follicle, or the uterus itself has ruptured.
In some cases, fertility treatment can cause the extra fluid.
Radiopaedia.Differential diagnosis of free fluid in cul de sac (pouch of Douglas).
2014;41(3):140-145. doi:10.5653/cerm.2014.41.3.140.
2016;105(6):1381-93. doi: 10.1016/j.fertnstert.2016.03.026.
