Interstitial line: sonographic finding in interstitial (cornual) ectopic pregnancy.
OBJECTIVE
To evaluate the relationship of the endometrial canal and decidua vera to the interstitial gestational sac and to determine if this relationship can be used to increase the predictive value of ultrasound (US) in the diagnosis of interstitial ectopic pregnancy.


METHODS
The US findings in 12 patients with interstitial ectopic pregnancy were reviewed. Radiologists also reviewed the cases of 40 patients with various diagnoses to assess the accuracy of the interstitial line sign.


RESULTS
US showed a definite gestational sac in four of the 12 patients (33%); the rest had a heterogeneous mass in the cornual region. Thinning of the myometrial mantle was seen in these four patients. The gestational sac appeared eccentric in three of these but in only three of 12 (25%) overall. The endometrial canal or interstitial portion of the tube was identified in 11 of 12 patients (92%). The interstitial line had better sensitivity (80%) and specificity (98%) than eccentric gestational sac location (sensitivity, 40%; specificity, 88%) and myometrial thinning (sensitivity, 40%; specificity, 93%) for the diagnosis of interstitial ectopic pregnancy.


CONCLUSIONS
The interstitial line sign is a useful diagnostic sign of interstitial ectopic pregnancy.
Section of Ultrasound Health Sciences Centre, Winnipeg, Manitoba, Canada.
T E
TE
Ackerman
C S
CS
Levi
S M
SM
Dashefsky
S C
SC
Holt
D J
DJ
Lindsay
D000328:Adult; D000650:Amnion / Q000000981:diagnostic imaging*; D002823:Chorion / Q000000981:diagnostic imaging*; D003656:Decidua / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D004717:Endometrium / Q000000981:diagnostic imaging*; D005260:Female; D005544:Forecasting; D006801:Humans; D015588:Observer Variation; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000000981:diagnostic imaging; D011274:Pregnancy, Tubal / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity; D014463:Ultrasonography