From the Guidelines
The presence of free fluid in the anterior and posterior cul-de-sac on transvaginal ultrasound is most commonly correlated with pelvic floor dysfunction, particularly with conditions such as pelvic organ prolapse (POP) or cul-de-sac hernias, as described in the ACR Appropriateness Criteria® for pelvic floor dysfunction in females 1.
The finding of free fluid in the cul-de-sac can be associated with various pelvic floor disorders, including cystocele, urethrocele, uterine/cervical prolapse, vaginal prolapse, rectocele, peritoneocele, enterocele, or sigmoidocele, as outlined in the study published in the Journal of the American College of Radiology 1.
- The clinical presentation of patients with these conditions often includes symptoms such as pelvic pressure or bulge, and may be accompanied by other associated pelvic floor dysfunction.
- The goals of imaging in this setting, as stated in the study 1, may include confirming clinically suspected prolapse, assessing the severity of prolapse, evaluating for associated structural defects or functional abnormalities, and determining the contents of cul-de-sac hernias.
- The appearance of these findings on imaging is well described in the literature, allowing for accurate diagnosis and management of pelvic floor dysfunction 1.
- It is essential to consider the clinical context and symptoms presented by the patient, such as acute pain, fever, or positive pregnancy test, to determine the underlying cause of the free fluid and guide further evaluation and management.
From the Research
Correlation of Free Fluid in Anterior Posterior Cul-de-sac
- The presence of free fluid in the anterior posterior cul-de-sac, as observed through transvaginal ultrasound, can be correlated to various conditions, including blunt abdominal trauma 2, pelvic pathology associated with increased peritoneal fluid 3, and ovarian malignancy 4.
- A study published in Radiology in 2001 found that free fluid isolated to the cul-de-sac is likely physiologic in female patients of reproductive age with trauma, and clinical follow-up should suffice 2.
- Another study published in The Journal of Reproductive Medicine in 1998 found that transvaginal ultrasound is a sensitive method of detecting the presence of > 8 mL of free pelvic fluid, and is an important diagnostic tool in the assessment of pelvic pathology associated with increased peritoneal fluid 3.
Quantitative Assessment of Accumulated Cul-de-sac Fluid
- A study published in the American Journal of Obstetrics and Gynecology in 1992 used high-frequency transvaginal ultrasonography to assess the correlation between various amounts of fluid installed in the cul-de-sac and ultrasonic imaging, and found that no fluid could be ultrasonically detected when the volume was less than 35 to 40 ml 5.
- The same study found that between 35 and 100 ml, there was a clear image of accumulated fluid in the cul-de-sac with good correlation between volume and image 5.
Prediction of Ectopic Pregnancy
- A study published in The American Journal of Emergency Medicine in 2002 found that patients with isolated abnormal cul-de-sac fluid at transvaginal ultrasound are at moderate risk for ectopic pregnancy, and the risk increases if the fluid is echogenic or the volume is large 6.
- The study found that ectopic pregnancy was diagnosed in 42% of patients with isolated cul-de-sac fluid, 22% of patients with a moderate amount of anechoic fluid, and 73% of patients with a large volume of fluid or any echogenic fluid 6.
Significance of Pelvic Fluid in Ovarian Cancer Screening
- A study published in Diagnostics in 2022 found that the presence of pelvic fluid during transvaginal ultrasonography is associated with ovarian malignancy, and that the odds ratio of detecting fluid significantly differed from that of the control group or benign ovarian tumors 4.
- The study found that the mean duration that pelvic fluid was present for women with true-negative screens was 2.2 ± 0.05 encounters, lasting 38.7 ± 1.3 months 4.