Serous culdocentesis in ectopic pregnancy: a report of two cases caused by coexistent corpus luteum cysts.

Two cases of women with large-volume serous culdocentesis results are presented. Both patients ultimately had ectopic pregnancies diagnosed surgically, and aspiration into coexistent corpus luteum cysts caused the "false-negative" culdocentesis results. The accuracy of culdocentesis and its continued role in the workup of the patient with possible ectopic pregnancy is reviewed. Because the corpus luteum is a cystic structure present in all pregnancies during the first seven weeks, cyst aspiration is always a possibility and should be suspected when large amounts of serous fluid are obtained by culdocentesis. Such results should be considered nondiagnostic and do not exclude a coexistent ectopic pregnancy.