Magnetic Resonance Imaging as an Adjunct to Ultrasound in Evaluating Cesarean Scar Ectopic Pregnancy
A 36-year-old woman (gravida 5, para 2) at approximately 8 weeks and 6 days gestation presented to her obstetrician complaining of heavy vaginal bleeding that had started 3 days prior. At the time of presentation, the vaginal bleeding had decreased to occasional spotting. The patient did not have abdominal pain or other constitutional symptoms. She also had no history of fibroids, endometriosis, or abnormal pap smears. She did report a medical history significant for beta thalassemia minor and a past surgical history of two prior cesarean sections for macrosomia. Serum beta-human chorionic gonadotropin (beta-hCG) level at the time of presentation measured 199,760 mIU/mL. A subsequent pelvic ultrasound showed a retroflexed gravid uterus with a single viable pregnancy in the lower uterine segment abutting the urinary bladder [Figure –]. Two- and 3-dimensional multiplanar views on the TVUS demonstrated a normal uterine fundus superior to the gestational sac. Fetal measurements were consistent with an estimated gestational age of 8 weeks and 5 days. Fetal cardiac activity measured 159 beats per minute (bpm). Given the position of the gestation in the lower uterine segment and the history of two prior cesarean sections, the findings on initial ultrasound examination raised the suspicion of a cesarean scar ectopic pregnancy with possible isthmic-cervical involvement [Figure –]. In addition, the proximity of the gestation to the urinary bladder raised the possibility of urinary bladder involvement; however, ultrasound examination could not exclude this possibility with certainty. The patient was referred to the hospital for admission, further evaluation with MRI, and medical management with the possibility of surgical intervention.\nMRI confirmed an intrauterine pregnancy bulging through the myometrium of the lower uterine segment with resultant mass effect on the superior right parasagittal aspect of the urinary bladder [Figure –] without direct invasion of the urinary bladder wall. The developing placenta was positioned inferiorly in this region with little or no surrounding myometrium. The findings on MRI were diagnostic of an ectopic pregnancy in the lower uterine segment, within the known cesarean scar, and confirmed the absence of urinary bladder involvement.\nUpon admission, conservative management was initiated. The patient underwent a successful bilateral uterine artery embolization via a right common femoral artery approach. The right uterine artery was embolized using five vials of 500-700 μm microspheres and stasis of blood flow was achieved. The left uterine artery was embolized using four vials of 500-700 μm microspheres and an additional vial of 700-900 μm microspheres with near stasis of flow. The patient also received systemic intramuscular methotrexate therapy (80 mg administered via the left gluteus muscle). Quantitative serum beta-hCG levels began to decrease, though fetal cardiac activity remained present and measured in the range of 160 bpm. A second dose of 80 mg intramuscular methotrexate was administered 3 days later with serum beta-hCG levels continuing to decline; however, follow-up serial ultrasound examinations continued to demonstrate fetal cardiac activity in the 160 bpm range. The patient was deemed to have failed initial conservative therapy and was given the option of an intra-amniotic injection of potassium chloride with methotrexate or a hysterectomy. The patient ultimately decided on surgical management and underwent a total abdominal hysterectomy with extensive lysis of adhesions. Intraoperative findings revealed the urinary bladder to be densely adherent to the lower uterine segment and the unruptured pregnancy, primarily on the right as demonstrated on the MRI. Pathologic evaluation of the hysterectomy specimen revealed a gravid leiomyomatous uterus with decidua in the uterine corpus as well as serosal adhesions to adipose tissue and skeletal muscle at the prior cesarean section scar. A portion of spongy, placental tissue measuring 5.0 × 4.0 × 2.7 cm was attached to the anterior lower uterine segment with extension to the upper endocervical canal. An embryo with four limb buds and ambiguous genitalia was present within the gestational sac [Figure –]. No cytotoxic effects related to the embolization or chemotherapy were reported.