Culdocentesis

INTRODUCTION — Culdocentesis is a procedure in which peritoneal fluid is aspirated from the posterior pelvic cul-de-sac (pouch of Douglas) through the posterior vaginal fornix. There are few indications for this procedure in current practice. However, there still remain areas in the world where ultrasound is not available. Historically, it was used to evaluate for hemoperitoneum secondary to ruptured ectopic pregnancy or ruptured ovarian cyst, or for a pelvic infection. However, this role has largely been replaced by evaluation with pelvic imaging, image-guided aspiration of fluid, and minimally invasive surgery.

The culdocentesis procedure is reviewed here. Other approaches to the evaluation of individuals with suspected pelvic bleeding or infection are discussed separately. (See "Evaluation and management of ruptured ovarian cyst" and "Pelvic inflammatory disease: Clinical manifestations and diagnosis" and "Ectopic pregnancy: Clinical manifestations and diagnosis".)

In this topic, when discussing study results, we will use the terms "woman/en" or "patient(s)" as they are used in the studies presented. We encourage the reader to consider the specific counseling and treatment needs of transgender and gender-expansive individuals.

INDICATIONS — Culdocentesis may be used to evaluate females with pain in the lower abdomen/pelvis to determine whether intraabdominal fluid is present and, if present, to reveal the nature of the fluid (eg, serous, purulent, bloody). Thus, the procedure can be helpful in evaluating those with a suspected ruptured ovarian cyst, pelvic inflammatory disease, or ruptured ectopic pregnancy [1-4]. (See "Evaluation and management of ruptured ovarian cyst" and "Pelvic inflammatory disease: Clinical manifestations and diagnosis" and "Ectopic pregnancy: Clinical manifestations and diagnosis".)

Ultrasound examination has largely replaced culdocentesis because it accurately identifies the presence of abdominal/pelvic fluid, is more comfortable for the patient, and provides additional information about the pelvis, such as whether there is an adnexal mass or intrauterine pregnancy. Findings on ultrasonography are especially useful when interpreted in conjunction with laboratory test results, such as a complete blood count and pregnancy test. However, culdocentesis may be useful when ultrasonography is not readily available or to obtain fluid directly from the peritoneal cavity. For example, culdocentesis is proposed as an alternative method for collecting peritoneal fluid for measuring tumor markers, to be used in conjunction with serum markers and microbial profiles, to aid in diagnosis of epithelial ovarian cancer [5] and may also be used to assess for salpingitis and pelvic infection. In the past, cytologic evaluation of peritoneal fluid obtained by culdocentesis was used to diagnose ovarian cancer, but culdocentesis is no longer routinely performed for this indication [6].

CONTRAINDICATIONS — Prior to the procedure, a bimanual examination should be performed to ascertain that the posterior cul-de-sac does not contain cysts, masses, or other structures that might contaminate the peritoneal cavity if perforated or that could impede access to free fluid in the posterior cul-de-sac. A fixed retroverted uterus or a bleeding diathesis are additional contraindications.

ANATOMY — Relevant anatomy is shown in the figure (figure 1).

INFORMED CONSENT — A consent form for culdocentesis should include the purpose of the procedure, explanation of what will happen in understandable terms, risks and complications, alternatives, and possible outcomes.

PREPARATION

●Review the patient's history to exclude signs/symptoms suggestive of a bleeding disorder.

●Perform a pelvic (bimanual) examination to assess the posterior cul-de-sac and identify possible pathology.

●Obtain written informed consent.

●Involve a trained medical interpreter for provision of education and discussion of informed consent if the patient speaks a different primary language from that of the examiner or clinician performing the procedure.

●Ask the patient to walk or sit upright for 10 to 15 minutes to allow abdominopelvic fluid to pool in the posterior cul-de-sac.

●Organize instruments for the procedure.

●Explain each step of the culdocentesis to the patient so she knows what to expect.

●Inquire about allergies to medications and iodine so these agents can be avoided.

MATERIALS

●Speculum – The medium Graves speculum is preferred. The Pederson speculum may be used for individuals with a narrow vagina or intact hymen (picture 1).

●Gloves.

●Single toothed tenaculum.

●18-gauge needle attached to a 20 mL syringe containing 5 mL of normal saline.

●Sterile swabs or sponges.

●Long handled ringed forceps.

●A suitable antiseptic, such as povidone iodine.

●Specimen containers.

●A local anesthetic (eg, 2 percent lidocaine gel).

●Ferris subsulfate (Monsel's solution) to control bleeding.

PROCEDURE

Anesthesia — A topical anesthetic applied to the posterior vagina and posterior cervical lip may provide some anesthesia; however, randomized trials have not consistently demonstrated a significant reduction in pain when compared with placebo [7,8]. Paracervical block or no anesthesia are other options. The failure rate of paracervical block can be as high as 18 percent and complications rarely occur [9,10].

Steps

●Place patient in the dorsal lithotomy position with the head of the examining table elevated 60 degrees to allow peritoneal fluid to pool in the posterior cul-de-sac.

●Insert speculum to visualize cervix.

●Cleanse vagina and cervix with antiseptic (povidone iodine).

●Apply 2 percent lidocaine gel to the posterior vagina and posterior cervical lip (optional). Needle puncture for anesthesia may be as painful as the procedure itself and may cause bleeding in the posterior cul-de-sac because the vaginal mucosa of the posterior fornix is very vascular. However, some clinicians opt to inject anesthesia into the submucosa of the site of puncture or posterior fornix [11].

●Grasp the posterior lip of the cervix with the tenaculum and lift the cervix slightly to expose the posterior fornix, which is bounded laterally by the uterosacral ligaments.

●Insert an 18-gauge needle attached to a 20 mL syringe containing 5 mL of normal saline (or air) through the posterior vaginal wall into the posterior cul-de-sac using a rapid, deliberate thrust. The insertion point is in the midline, approximately 1 to 2 cm below the insertion of the uterosacral ligaments onto the uterus and inferior to posterior border of the vaginal mucosa and the cervix (in the posterior vaginal fornix). At that point, the insertion of the needle into the vaginal mucosa will enter posterior pelvic cul-de-sac. The needle should not extend more than 3 to 4 cm through the vaginal mucosa and is directed slightly caudad, away from the uterus and toward the sacrum.

An 18-gauge needle is suggested to avoid clotting and increase the yield of the sample. The large needle size may slightly increase the risk of vascular puncture; however, puncture is rare in experienced hands.

●Inject 5 mL of normal saline (preferred, although air can also be injected) to confirm placement and clear tissue from the needle point. Reposition the needle if there is resistance.

●Aspirate peritoneal fluid, and then remove the needle slowly (figure 1). If no fluid is obtained, repeat the procedure at a different angle with a new needle. Discontinue the procedure if unsuccessful after two or three attempts.

INTERPRETATION OF FINDINGS — Subsequent steps depend upon type of aspirated fluid.

●A small amount of clear fluid is normal. Copious peritoneal fluid suggests a ruptured fluid filled cyst or ascites.

●No fluid in the posterior cul-de-sac can also be a normal finding. However, a dry tap is considered unsatisfactory and suggests that the needle tip is obstructed by tissue due to poor positioning, adhesions, or other pathology.

●Nonclotting blood indicates active intraperitoneal bleeding. Determine the hematocrit: A hematocrit over 15 percent is most consistent with hemorrhage from a ruptured ectopic pregnancy or actively bleeding ruptured corpus luteum while a hematocrit less than 8 percent is more consistent with blood tinged fluid from a ruptured ovarian cyst or pelvic inflammation. Injection of 5 mL of saline as above does not significantly impact the hematocrit of the peritoneal fluid unless minimal fluid is aspirated. (See 'Steps' above.)

●Clotting blood suggests blood from a vein or artery may have been aspirated. The most common site of vessel perforation is the uterine vein. Remove the needle, reinsert a new needle, and aspirate again. The 18-gauge needle is suggested to avoid clotting and increase collected sample yield. The slightly larger needle may slightly increase the risk of puncture. However, risks of puncture are rare in experienced hands.

●The presence of pus indicates an infectious process, possibly as abscess. Further evaluation of the source of pus can include further exploration using a blunt instrument or gentle exploration with a finger. Sending the aspirate for culture and gram stain may assist with evaluation. Anaerobic cultures typically require a minimum sample of 5 mL; we aim to submit 5 to 10 mL of aspirate.

The incidence of a false positive test for nonclotting blood is less than 2 percent. The presence of nonclotting blood, particularly in a hemodynamically unstable patient, indicates a need for stabilization and surgery to identify and treat the source of bleeding (see "Tubal ectopic pregnancy: Surgical treatment"). Additional tests may be indicated prior to surgery, as time permits, depending on the individual clinical circumstances. As an example, if the pregnancy test is negative then a nongynecologic source of bleeding should be considered. In trauma patients, the possibility of hepatic or splenic rupture should be suspected and a general surgeon consulted.

Purulent fluid indicates infection. Pelvic inflammatory disease is the leading gynecologic cause, but nongynecologic etiologies should also be considered (eg, appendicitis, diverticulitis). (See "Pelvic inflammatory disease: Clinical manifestations and diagnosis" and "Pelvic inflammatory disease: Treatment in adults and adolescents" and "Causes of abdominal pain in adults".)

Aspiration of clear fluid merely indicates that there is no collection of pus or blood in the pelvis. It does not exclude the possibility of an unruptured ectopic pregnancy, ovarian cyst, tubal infection, or other gynecologic or nongynecologic pathology. Further evaluation is needed.

COMPLICATIONS — Serious complications are rare. There is risk of puncturing the anterior division of the internal iliac vessels or the obturator or pudendal nerve. Inadvertent bowel perforation generally does not lead to morbidity. Air-embolism has not been reported.

FOLLOW-UP CARE

●The patient may resume normal activities after the procedure.

●Acetaminophen or ibuprofen are recommended to relieve minor pain, if needed.

●Instruct the patient to notify her health care provider if she has excessive vaginal bleeding (eg, greater than one pad per hour), fever, purulent vaginal discharge, worsening or persistent pelvic pain, myalgia, or nausea and vomiting.

SUMMARY AND RECOMMENDATIONS

●Description and indications – Culdocentesis is a procedure in which peritoneal fluid is aspirated transvaginally from the posterior cul-de-sac (pouch of Douglas). It may be used to evaluate patients with pain in the lower abdomen/pelvis to determine whether intraabdominal fluid is present and, if present, to reveal the nature of the fluid (eg, serous, purulent, bloody). The procedure aids in diagnosis of ruptured ectopic pregnancy, ruptured ovarian cysts, pelvic inflammatory disease, and other findings associated with fluid in the pelvis. (See 'Introduction' above and 'Indications' above.)

Although not generally used in clinical environments with access to ultrasound, culdocentesis remains a viable option in resource-limited areas and areas with the need for emergency diagnosis of ruptured ectopic pregnancy in an unstable patient. (See 'Indications' above.)

●Procedure

•A bimanual pelvic examination is performed before the procedure to ascertain that the posterior cul-de-sac does not contain structures that might contaminate the peritoneal cavity if perforated or that could impede access to free fluid in the posterior cul-de-sac. (See 'Contraindications' above.)

•An 18-gauge needle attached to a 20 mL syringe containing 5 mL of normal saline (or air) is inserted through the posterior vaginal wall into the cul-de-sac and then negative pressure is applied to suction any available fluid into the syringe. (See 'Procedure' above.)

●Interpretation of findings – Detection of a small amount of clear fluid is normal. Copious clear fluid suggests a ruptured fluid filled cyst or ascites. No fluid in the posterior cul-de-sac can be a normal finding; however, a dry tap is considered unsatisfactory and suggests that the needle tip is obstructed by tissue due to poor positioning, adhesions, or other pathology. Nonclotting blood indicates active intraperitoneal bleeding. Clotting blood suggests blood from a vein or artery may have been aspirated. Pus indicates an infectious process, possibly as abscess. (See 'Interpretation of findings' above.)

●Risks – Risks of culdocentesis include puncturing bowel, the uterine wall, and an ovarian mass. However, culdocentesis is a low-risk procedure when performed by a skilled clinician. (See 'Complications' above.)