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.1–9 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. Sensation
of the vagina is greatest near the introitus. There is minimal sensation
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 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. Approximately 85 to 90
percent of patients with ruptured ectopic pregnancies have a positive
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 percent 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 a physician that following serial quantitative beta-HCG levels
can be performed before committing a stable patient to an operative
procedure. A positive culdocentesis would indicate intraabdominal