Can ultrasound reliably diagnose ectopic pregnancy?

A total of 252 women with amenorrhoea and with abdominal pain or vaginal bleeding, or both, had an emergency high-resolution ultrasound sector scan. In 100 women the symptoms were unrelated to any identifiable abnormal ultrasound finding, none of them was pregnant and their symptoms settled spontaneously; 33 other women had follicular or luteal cysts and 30 had pelvic inflammatory disease. Histological examination confirmed an ectopic pregnancy in 60 women (24%); in seven a live fetus was observed outside the uterus allowing a confident diagnosis of ectopic pregnancy; in 27 the thickness of the endometrium was greater than 10 mm (sensitivity 50%, specificity 84%, positive predictive value 28%, negative predictive value 87%); in 15 the uterine area measurement was less than 20 cm2 (sensitivity 72%, specificity 41%, positive predictive value 20%, negative predictive value 79%); and 43 had an adnexal mass volume greater than 10 ml separate from the ovary (sensitivity 85%, specificity 37%, positive predictive value 23%, negative predictive value 90%). Only three had negative ultrasound findings. The negative predictive value of an ultrasound examination could be increased to 96% by using a combination of these ultrasound features. The addition of hCG (greater than 25 i.u./l) improved the specificity to 98% and the negative predictive value to 100%. These criteria may improve the ultrasound diagnosis of ectopic pregnancy.