What is culdocentesis?

Culdocentesis is a medical procedure that checks for abnormal fluid behind your vagina and under your uterus in an area called the posterior cul-de-sac. Your healthcare provider inserts a thin needle through your vaginal wall to obtain a sample of fluid from this area for testing.

Transvaginal ultrasound has largely replaced culdocentesis because it can detect abdominal and pelvic fluid. Surgeons may use minimally invasive or image-guided surgical techniques instead of culdocentesis.

What is the cul-de-sac?

Women or people assigned female at birth (AFAB) have two cul-de-sacs — an anterior (in the front) and a posterior (in the back). Your anterior cul-de-sac is between your bladder and uterus. Your posterior cul-de-sac is between your uterus and rectum (behind your vagina). The posterior sac is also known as the pouch of Douglas. Fluid may accumulate in the posterior sac if you have certain medical conditions. Culdocentesis is a diagnostic procedure to extract fluid from the pouch of Douglas (or posterior cul-de-sac) to test it for problems.

When is culdocentesis performed?

Certain medical conditions and infections cause irregular fluid to fill your posterior cul-de-sac. Most healthcare providers use an ultrasound to detect fluid behind your uterus. If they suspect the fluid is abnormal, they may perform culdocentesis to extract fluid for testing.

Some reasons for culdocentesis are:

Test Details

What is the purpose of culdocentesis?

Your provider may perform culdocentesis when they need to remove fluid from behind your vagina and test it for infection.

How do I prepare for culdocentesis?

You don’t need to do much to prepare for culdocentesis. Your provider may suggest you remain still or sit for several minutes before the test. Since you’ll probably receive anesthetic medication to numb your vagina, you may need someone to drive you home afterward.

How is culdocentesis performed?

The steps of the procedure typically involve:

  • Your healthcare provider will perform a pelvic exam and insert a surgical instrument to lift your cervix up. This shouldn’t be painful but may be uncomfortable.
  • You provider numbs an area of your cervix with a local anesthesia.
  • Your provider inserts a thin needle through the wall of your vagina below where your cervix ends. The needle is attached to a syringe that collects fluid.
  • Finally, your provider removes a sample of fluid from your posterior cul-de-sac through the needle.

The fluid sample is sent to a lab for testing. You may be uncomfortable or feel crampy after culdocentesis, but this should subside within 24 to 48 hours.

Is the test painful?

No, culdocentesis shouldn’t be painful. You’ll get medication that numbs the area where your provider inserts the needle. Cramping and mild discomfort may occur.

You may need someone to take you home if you were given medications to relax.

What are the risks of culdocentesis?

Risks of culdocentesis include:

  • Puncturing your uterus or rectum.
  • Infection.
  • Puncturing blood vessels, cysts or tumors.

How is ectopic pregnancy diagnosed using culdocentesis?

This procedure was once valuable in diagnosing ruptured ectopic pregnancies with hemoperitoneum (bleeding) when ultrasound wasn’t yet widely available. During this time, ectopic pregnancies weren’t detected until they ruptured. However, ultrasound can detect an ectopic pregnancy before it ruptures which reduces the need for culdocentesis.

Care at Cleveland Clinic

Results and Follow-Up

What do the results of culdocentesis mean?

A normal result means your fluid is clear. Bloody, pus-filled or large amounts of clear fluid may suggest there’s a problem.

For example, yellow, pus-filled fluid indicates an infection. Blood that doesn’t clot means an ectopic pregnancy has ruptured. This is because blood from your cul-de-sac area doesn’t clot.

The fluid may need drained or treated with antibiotics depending on the test results.

When should I call my doctor?

Contact your healthcare provider if you have severe pain in your abdomen or pelvis. This could suggest a problem. If you’ve had culdocentesis, call your provider if you experience heavy bleeding, pain or flu-like symptoms.

Additional Details

What’s the difference between culdocentesis and colpocentesis?

Colpocentesis is an outdated term for culdocentesis. They’re the same procedure.

What’s the different between culdocentesis and amniocentesis?

Amniocentesis is a procedure where your provider removes amniotic fluid from your uterus during pregnancy to test for infection or chromosomal abnormalities.

A note from Cleveland Clinic

Culdocentesis is a procedure to remove abnormal fluid from the pouch of Douglas or your posterior cul-de-sac. This area located behind your vagina can fill with irregular fluid if you have certain conditions or infections. Ultrasound has replaced culdocentesis in detecting fluid in your pelvic region, so the use of culdocentesis has decreased. Your provider may use other techniques to remove abnormal fluid from your posterior cul-de-sac.

Last reviewed by a Cleveland Clinic medical professional on 08/31/2022.


  • Kho RM, Lobo RA. Ectopic pregnancy: etiology, pathology, diagnosis, management, fertility prognosis. ( In: Lobo RA, Gershenson DM, Lentz GM, Valea FA, eds. Comprehensive Gynecology. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 17. Accessed 8/31/2022.
  • Herd AM, Sokal J. Case report: atypical ectopic pregnancy and culdocentesis. Still a valuable emergency medicine procedure. ( Can Fam Physician. 2001 Oct;47:2057-8, 2061. Accessed 8/31/2022.
  • Lafans K, Kok SJ. Culdocentesis. ( [Updated 2022 May 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Accessed 8/31/2022.
  • Sivalingam VN, Duncan WC, Kirk E, Shephard LA, Horne AW. Diagnosis and management of ectopic pregnancy. ( J Fam Plann Reprod Health Care. 2011 Oct;37(4):231-40. Accessed 8/31/2022.

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