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.1-11 Culdocentesis involves introducing a hollow needle through the posterior vaginal cuff and into the peritoneal space.1-11 This is a relatively simple and fast procedure. Ultrasound (US) has virtually replaced culdocentesis as the test of choice. US is minimally invasive, has high sensitivity, has a high specificity, and involves no ionizing radiation. Culdocentesis may still prove to be an important skill for the Emergency Physician to consider using for unstable patients and in low-resource settings that do not have US capabilities.
ANATOMY AND PATHOPHYSIOLOGY
The key anatomy to be familiar with is the vagina and the posterior cul-de-sac (i.e., the rectouterine pouch or the pouch of Douglas). The posterior cul-de-sac is formed by reflections of the peritoneum between the posterior surface of the uterus and the anterior surface of the rectum (Figure 171-1). 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 posterior cul-de-sac 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 posterior cul-de-sac. The sensory innervation of the vagina is greatest near the introitus. There is minimal sensory innervation in the posterior vaginal fornix adjacent to the posterior cul-de-sac.
Anatomy of the female pelvis. A. Midline sagittal view. B. View from above inside the pelvis.
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 US, and increased resolution of US. Recent studies have clearly shown US to be more sensitive and noninvasive in detecting a hemoperitoneum.1
The primary indication for this procedure is a hemodynamically unstable female patient of reproductive age with evidence of peritoneal irritation in the pelvic region when bedside US is not available. 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 US if there is any diagnostic uncertainty. A culdocentesis may be performed if bedside US is not available. Approximately 85% to 90% of patients with ruptured ectopic pregnancies ...