Isolated fluid in the cul-de-sac: how well does it predict ectopic pregnancy?

We examined the risk of ectopic pregnancy among patients with isolated abnormal cul-de-sac fluid at transvaginal ultrasound. We conducted a retrospective cohort study of all ED patients presenting January 1995 to August 1999 with abdominal pain or vaginal bleeding and a positive beta-hCG test. The risk of ectopic pregnancy in patients with a moderate volume of anechoic fluid was compared with those with either a large volume of anechoic fluid or any echogenic fluid. Ectopic pregnancy was diagnosed in 16/38: 42%(95% CI 26%-59%) of patients with isolated cul-de-sac fluid, 5/23: 22% (95% CI 7%-42%) of patients with moderate amount of anechoic fluid, and 11/15: 73% (95% CI 45%-92%) of patients with a large volume of fluid or any echogenic fluid. These differences were significant (P =.005). Patients with isolated abnormal cul-de-sac fluid are at moderate risk for ectopic pregnancy. The risk increases if the fluid is echogenic or the volume is large.