Culdocentesis

Anatomy and Physiology

On the sagittal cross-section of the female pelvis, the urinary bladder sits most anteriorly, just behind the pubic bone. Moving posteriorly lies the uterus, which lies on top of the urinary bladder. The long axis of the uterus is perpendicular to the long axis of the vagina and where these two lines meet is the location of the cervix. There is a potential space just posterior to the uterus known as the pouch of Douglas (rectouterine pouch or cul-de-sac) that is separate from the uterus by the rectouterine septum. The pouch of Douglas is where blood can potentially pool if there is bleeding within the peritoneal cavity. Behind the pouch of Douglas is the rectum.

Indications

Indications include clinical suspicion of ruptured ectopic pregnancy and hemoperitoneum. Signs and symptoms include a positive pregnancy test or elevated beta-human chorionic gonadotropin, abdominal pain, vaginal bleeding, peritoneal signs such as rigidity and rebound, rectal pressure, and hemodynamic instability, namely tachycardia, and hypotension.

Contraindications

Contraindications include a known mass or retroverted uterus that occupies the pouch of Douglas.[1][5]

Equipment

Equipment includes speculum, lubricated jelly, a Foerster sponge forceps (ring forceps), sterile gauze/sponges, iodine solution, a tenaculum (or Vulsellum forceps), 18 gauge spinal needle (5 cm long), 10 mL syringe (three-finger control syringe), lidocaine, and gloves.[5]

Personnel

To carry out the procedure, a proceduralist (physician, physician assistant, or nurse practitioner) and a nurse or nursing aide are needed.

Preparation

To prepare for a culdocentesis, have the supplies ready on a table near the proceduralist. Use good sterile technique when preparing supplies. Have a nurse or nursing aide present in the room to help hand over supplies. The patient should lay in the lithotomy position, preferably on a cart with stirrups for patient comfort.

Technique or Treatment

The procedure should start with a bimanual examination to assess the adnexa and cervix for cervical motion tenderness, uterus including uterine position, and cul-de-sac mass or tenderness. Then a speculum exam should be performed by lubricating a speculum and inserting it into the vagina. Foerster sponge forceps should be used to introduce iodine-soaked gauze to cleanse the cervix and posterior fornix. Apply a tenaculum or Vulsellum forceps to the lower lip of the cervix, be sure to warn patients about potential cramps during this part of the procedure. Move the tenaculum to expose the posterior fornix of the vagina. Usually, this involves moving the cervix forward and anterior. Anesthetize the mucosa about 1 cm below the posterior rim of the cervix with lidocaine. Use an 18 gauge 10 cm long needle attached to a 10 mL syringe with 2 to 3 mL of air or sterile saline and insert the needle tip 1 cm below where the cervix ends in the posterior fornix. Advance the needle 3 to 4 cm and inject the air or saline. If there is resistance when injecting the air or saline, reposition the needle until no resistance is felt. The needle should enter the Pouch of Douglas (rectouterine pouch or cul-de-sac). Aiming the needle towards the sacrum and away from the uterus may help with positioning. Lastly, attempt to aspirate. The procedure should be stopped if three attempts produce no fluid return.[3][5][6]

Complications

Complications include accidental puncture of visceral organs, the rectum, or the uterus. Puncture of blood vessels, cysts, or tumors. Aspiration of products of an ectopic pregnancy, peritoneal introduction of infected or malignant cancer-carrying cells.[1][5]

Clinical Significance

Once the aspirated peritoneal fluid is obtained, it can be analyzed microscopically and cultured.[3] Blood that is retrieved from the pouch of Douglas from the hemoperitoneum does not clot due to the process of defibrination. If the bleeding is brisk, however, the blood does clot. A positive culdocentesis is determined by the aspirated blood having a hematocrit of 0.15 or greater (15 % or greater). A non-diagnostic culdocentesis occurs when clotted blood is obtained, or no fluid is aspirated at all. The blood will clot if the needle inadvertently punctures an artery or vein.[3] 

False-negative culdocentesis can occur in non-ruptured ectopic pregnancies or if the Pouch of Douglas is destroyed from endometriosis or scarring due to pelvic inflammatory disease.[7] Most notably, a negative culdocentesis should not exclude the diagnosis of ruptured ectopic. The further away from ectopic implants from the body of the uterus, the less extensive the bleeding that will occur. Likewise, the closer the ectopic is to the body of the uterus, the more significant the amount of bleeding.[8] 

In a comparative study performed in 1998, researchers set out to identify if culdocentesis was comparable to sonography in the diagnosis of hemoperitoneum in 46 patients, 40 of which had an ectopic pregnancy. The study results found that ultrasound showed 100% specificity and 100% sensitivity in identifying hemoperitoneum. Culdocentesis had 80% specificity and 66% sensitivity. The negative predictive value of a non-diagnostic culdocentesis was 25%. The negative predictive value of sonography was 100% when no fluid was found on ultrasound.[1] Thus, culdocentesis has fallen out of favor compared to ultrasound for aiding in diagnosing hemoperitoneum because sonography has higher sensitivity and specificity than culdocentesis.

Enhancing Healthcare Team Outcomes

Rapid diagnosis of ruptured ectopic pregnancy is paramount to good patient outcomes. In high socioeconomic countries, ectopic pregnancy accounts for 1% to 2% of pregnancies, and it remains a leading cause of early maternal morbidity.[2] Multiple people from different professions must come together to diagnose, manage, and treat ruptured ectopic pregnancy. It often starts with nurses and emergency medical service providers who monitor the patient's vital signs and administer pain medications and fluids. Often these patients are hemodynamically unstable, and abnormal vital signs such as hypotension and tachycardia are the first indicators that there is a rupture. Next, the emergency physician evaluates the patient and often makes the diagnosis, but patient care does not stop there.

Laboratory technicians must process labwork promptly, including the beta-human chorionic gonadotropin level and hemoglobin, and view fluid under microscopy. Blood blank personnel may need to be involved if the patient has hemorrhagic shock and requires blood products. Pharmacists are involved in dosing pain medications and/or tranexamic acid. Radiologists interpret ultrasound images (if ultrasound is available) to aid in diagnosis. Consulting physicians such as obstetric/gynecologic physicians or if obstetrics/gynecology is unavailable, general surgeons should be on standby for emergent surgery if a patient presents with a ruptured ectopic. Often these patients need to be monitored for several days, and the physicians, advanced practice providers, nurses, and nurses' aids on the inpatient floors monitor and observe these patients. It truly takes a team to orchestrate the care for these patients, and each individual has an important role to play in ensuring the best possible outcomes for these patients.