Typical imaging findings in a caesarean scar ectopic pregnancy – A case report

A 28-year-old female presented with amenorrhea for 6 weeks, abdominal pain and minimal per vaginal bleeding for a few days. She had a positive urine pregnancy test. Her obstetric history was G4P2L2A1, with both previous deliveries by caesarean section.

She had done a transabdominal ultrasound in an outside centre, which revealed an empty endometrial cavity with a cystic structure in the anterior myometrium at the scar site, suspicious of a gestational sac. No obvious yolk sac or foetal pole was visualised and thus was referred to our centre for confirmation. MRI was performed, which revealed a bulky uterus (Figures 1a and 1b) with an anterior uterine myometrial defect and a cystic lesion within the defect. The cystic lesion was extending into the uterine canal posteriorly. Minimal pelvic collection was also noted. A transvaginal ultrasound was performed (Figures 2a and 2b), revealing the gestational sac at the anterior myometrial scar site, which was extending towards the endometrial cavity. The yolk sac and foetal pole were visualised with crown rump length (CRL) corresponding to 5 weeks of gestation. The foetus showed cardiac activity (Figure 4).

Background

Ectopic pregnancy refers to the implantation of a fertilised ovum outside of the uterine cavity. The overall incidence of ectopic pregnancy is estimated to be 2% of all pregnancies [1]. The most common site for ectopic pregnancy is the ampulla of the fallopian tube [1]. However, the implantation can occur in multiple other sites of the fallopian tubes, cervix, ovaries, scar sites and abdomen. Scar ectopic is one the rare causes of ectopic pregnancy and accounts for approximately 1 in 2000 of the pregnancies [2]. With the recent trend of increase in caesarean sections, there is an increase in the incidence of caesarean scar ectopic as well [3].

Clinical Perspective

Ectopic pregnancy usually presents in the first trimester as abdominal pain and per vaginal bleeding. In case of a ruptured ectopic, the patient can present in a hemodynamically unstable state. The presentation is similar in a case of caesarean scar ectopic. Transvaginal ultrasound, along with transabdominal ultrasound, is the modality of choice for the diagnosis of these ectopic pregnancies. MRI can be used for confirmation as well. Early diagnosis is really important in these cases as delay in diagnosis can be fatal at times.

Imaging Perspective

Ultrasonograhic findings hold the key to early diagnosis of caesarean scar ectopics. The important ultrasound findings that aid diagnosis are empty uterine cavity [4], thin myometrium at the implantation site [2], discontinuity in the anterior uterine wall in sagittal view [5], and gestational sac at lower uterine segment at previous caesarean section site [6]. The Doppler examination shows increased colour flow around the gestational sac [5,7]. All these findings were present in our case. After the implantation, the sac can extend either into the endocervical/endouterine canal, as in our case, or it can extend deep into the myometrium or towards the uterine serosal surface [5,8]. MRI was done in our case for confirmation of the pathology.

Outcome

The scar ectopic pregnancy can be managed medically with methotrexate or surgically with laparotomy and removal of the scar with the sac. A substantial number of authors prefer surgery over medical management [1]. Our case was managed with surgery and the patient was doing well after the surgery.

Take Home Message / Teaching Points

With the increasing trend of caesarean section, complications like scar ectopic are also in the rising trend. So, caesarean section should be limited to the case where it is strictly indicated. Imaging with ultrasound is vital to rule out scar ectopic in females with suspicious history and previous history of caesarean section.