The accuracy of first trimester ultrasound in the diagnosis of hydatidiform mole

Abstract

Objective: Previous studies have examined ultrasound findings in histopathologically confirmed cases of hydatidiform mole. The aim of this study was to assess the first-trimester ultrasonographic findings in all women suspected of having hydatidiform mole on ultrasound and those subsequently diagnosed with hydatidiform mole after histological examination of removed products of conception after surgical evacuation of the uterus. The aim was to obtain a true sensitivity and positive predictive value for ultrasound in the diagnosis of hydatidiform mole.

Methods: A retrospective analysis was performed of all cases of sonographically suspected hydatidiform mole and histologically proven hydatidiform mole presenting to the Early Pregnancy Unit of an inner city hospital over a 4-year period. The sensitivity and positive predictive value (PPV) of ultrasound in the detection of histologically proven hydatidiform mole was calculated.

Results: The study group consisted of 90 women; 56 were suspected of having hydatidiform mole on ultrasound, and of these 27 (48%) had hydatidiform mole confirmed after histopathological examination of the products of conception, while no changes suggestive of hydatidiform mole were present in the other 29 cases. Overall, 61 women had hydatidiform mole confirmed on histology-41 (67%) partial hydatidiform moles (PHM) and 20 (33%) complete hydatidiform moles (CHM). The ultrasound findings in the 34 cases not suspected of hydatidiform mole were an empty sac in 8/34 (24%) women and a delayed miscarriage in the other 26/34 (76%). The overall sensitivity and positive predictive value for the ultrasound diagnosis of hydatidiform mole was 44% and 48%, respectively. For PHMs the respective values were 20% and 22% and for CHMs they were 95% and 40%.

Conclusion: Ultrasonography is more reliable for diagnosing CHMs than for PHMs. Overall, the sensitivity of ultrasound for accurately predicting hydatidiform mole is 44%, and one in two women with an abnormal scan will have the disease confirmed on histology.