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Culdocentesis is a procedure used to sample peritoneal fluid to help confirm a diagnosis or to obtain a culture. It has mainly been used for diagnosing a ruptured ectopic pregnancy or ruptured ovarian cyst.19 Culdocentesis involves introducing a hollow needle through the posterior vaginal cuff and into the peritoneal space. This is a relatively simple and fast procedure. Ultrasound, with its improved resolution and availability, has virtually replaced culdocentesis as the test of choice.

The key anatomy to be familiar with is the vagina and the pouch of Douglas, also known as the rectouterine pouch or the cul-de-sac. The rectouterine pouch is formed by reflections of the peritoneum between the posterior surface of the uterus and the anterior surface of the rectum. It is the most dependent intraperitoneal space in both the upright and supine positions. This allows blood, pus, and other free fluids to pool in this space. The rectouterine pouch separates the upper portion of the rectum from the uterus and the upper portion of the vagina. The small intestine and a small amount of peritoneal fluid often lie within the rectouterine pouch. The sensory innervation of the vagina is greatest near the introitus. There is minimal sensory innervation in the posterior vaginal fornix adjacent to the rectouterine pouch.

Culdocentesis has been used in the Emergency Department in the past to diagnose a ruptured viscus, particularly an ectopic pregnancy. The use of culdocentesis has decreased significantly with the emergence of improved serum and urine tests for pregnancy, increased accessibility to ultrasonography, and the increased resolution of ultrasound. Recent studies have clearly shown ultrasonography to be more sensitive and noninvasive in detecting a hemoperitoneum.1 Despite this, there still remains three main indications to perform a culdocentesis.

The first indication is a hemodynamically unstable female patient of reproductive age with evidence of peritoneal irritation in the pelvic region. This patient most likely has a ruptured ectopic pregnancy and needs emergent surgery. A diagnostic test is usually not necessary to take the patient directly to the Operating Room if a rapid pregnancy test is positive. An unstable patient cannot be sent to the Radiology Department for an ultrasound. A culdocentesis may be performed if bedside ultrasonography is not available. Many Emergency Departments now have the availability of bedside ultrasound or have Radiology Technician available to perform bedside ultrasounds. Approximately 85% to 90% of patients with ruptured ectopic pregnancies have a positive culdocentesis.2

The second indication for a culdocentesis is a stable pregnant patient with ultrasonographic evidence of free fluid in the pelvis or pouch of Douglas. A culdocentesis can confirm if the fluid is blood. Approximately 65% to 70% of patients who have a stable presentation and unruptured ectopic pregnancy have a positive culdocentesis.

A culdocentesis is indicated if ultrasonography or laparoscopy is not readily available. A negative culdocentesis may be used to reassure the Emergency Physician that ...

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