Chronic ectopic pregnancy--two cases of acute rupture despite negative beta hCG.

We present the cases of two women with chronic ectopic pregnancies who presented with acute tubal rupture and hemoperitoneum despite negative beta-human chorionic gonadotropin (beta hCG) pregnancy tests. The appropriate screening use of beta hCG assays to ascertain pregnancy status, the mechanisms by which ectopic pregnancy may be seen with negative beta hCG tests, and the limitations of various assays are discussed. One patient, not initially believed to be pregnant, underwent computed tomography (CT) scan. Experience with use of CT scan in ectopic pregnancy diagnosis is limited; our case illustrates some of the possible CT scan findings. These cases illustrate the potential for ectopic pregnancy to rupture with low, if not undetectable beta hCG hormone levels, and consequently why it is not recommended to rely on quantitative beta hCG levels to guide the decision to proceed with ultrasound imaging.