Imaging and Clinical Presentation of Caesarean Scar Pregnancy

Objective: To evaluate transabdominal and transvaginal ultrasound for diagnosing Caesarean scar pregnancy. Methods: This is a retrospective study of patients diagnosed with Caesarean scar pregnancy in a tertiary referral centre from March 2010 to February 2015. Patient demographics were retrieved from the hospital electronic patient record system. Transabdominal and transvaginal ultrasound scans at the first visit to our centre were reviewed by two radiologists by consensus for the presence of five sonographic signs including empty uterine cavity, empty endocervical canal, gestational sac embedded in low uterine segment/hysterotomy scar, thin/absent myometrium between the gestational sac and bladder, and angular appearance of gestational sac. The sensitivity of each sign was compared using McNemar's test. Results: Fifteen patients (mean age 34.5 128-40] years. mean gestational age 8 weeks 1 day [4 weeks 5 days to 15 weeks 0 days] were included in the analysis. The majority of patients had only one previous Caesarean section (73%). The most common presenting compliant was vaginal bleeding (87%). The ratio between viable and nonviable scar pregnancy was 2:1. Transabdominal ultrasound was inferior to transvaginal ultrasound at detection of thin/absent myometrium (20% vs. 87%, p = 0.002) as well as angular appearance of gestational sac (333% vs. 67%, p = 0.031). Subgroup analysis showed that transabdominal ultrasound was reliable for prediction of thin! absent myometrium in the late first or early second trimester. Conclusions: Caesarean scar pregnancy is a potentially life-threatening condition and accurate diagnosis requires a high index of suspicion. Transabdominal ultrasound is a useful adjunct to transvaginal ultrasound in the diagnosis of Caesarean scar pregnancy.