Magnetic resonance imaging after laparotomy of fetal evacuation in advanced abdominal pregnancy

Abstract

Abdominal pregnancy (AP) is a rare event of globally reported pregnancy and is significantly challenging to diagnose because of various symptoms. Therefore, we aimed to present a case of a 26-year-old female with unexpected AP of third pregnancy found during emergency fetal evacuation laparotomy. The possible scenario was found to be fetus implanted into the fibroid scar of her obstetric history, leading to complications with uterine rupture. The image was observed properly by the MRI that was performed after the laparotomy. Although the ultrasound was used as the diagnostic tool for the AP, the MRI had an excellent ability to show detailed anatomy as a reliable imaging modality for patients with complicated obstetric history.

Introduction

Abdominal pregnancy (AP) is a pregnancy where implantation occurs in the peritoneal cavity, referring to omentum, abdominal vital organ, or large vessels [1,2]. It is the rarest type of ectopic pregnancy, accounting for 1.3%-1.4% of all cases which occur between 1:10,000 and 1:30,000 of globally reported pregnancy [3]. AP is divided into 2 types, namely primary and secondary. Primary AP is diagnosed by Studdiford's criteria [4], showing (1) bilateral fallopian tube and ovaries are normal, (2) uteroperitoneal fistula is absent, (3) a pregnancy related to the peritoneal surface and early enough to eliminate the possibility of secondary implantation following a primary nidation in the tube. The secondary AP occurs when the embryo grows in the abdominal cavity after it is expulsed from the fallopian tube or primary seat [4]. Despite the frequent occurrence, advanced secondary AP has higher mortality and morbidity for the mother and fetus. Magnetic resonance imaging (MRI) is not commonly used as a diagnostic tool during pregnancy of AP or for evaluating imaging postsurgical of unexpected cases.

Case report

A 26-year-old pregnant woman presented a complicated obstetric history with a cesarian section at first pregnancy due to placenta previa, 8 years ago. During the second pregnancy, patient had AP and received a laparotomy. After 2 years, patient came to the obstetric clinic to examine the third pregnancy and observation showed intrauterine pregnancy, good condition fetus, and no abdominal pain until the last session of the prenatal visit. At 31-32 weeks’ gestation, patient was subjected to emergency fetal evacuation laparotomy due to fetal death. The result of the laparotomy was unexpected, an intact membrane was found covered by the omentum after the incision. There was an unviable fetus with a twisted umbilical cord (Fig. 1). Subsequently, patient received a postsurgery MRI and found that there were placental remains with air component and connected to vagina, and uterine defects at the superoanterior aspect of uterine wall surrounded by fibrous tissue, as shown in Figure 2.

Fig. 1.

Surgery results were intraabdominal pregnancy with intact amniotic sac (left Figure), twisted umbilical cord (yellow arrow) around the fetus’ head (yellow dashed arrow), and placenta (white arrow) surrounded by omentum (yellow star).

Fig. 2.

T2-weighted sagittal view of MRI post laparotomy of the third pregnancy found that there was retained placenta with air component, surrounded by fibrous tissue, connected to vagina (yellow circle) with uterine defect (red line) on the anterosuperior aspect of uterine wall.

Discussion

AP is a pregnancy where implantation occurs in the peritoneal cavity, referring to omentum, abdominal vital organ, or large vessels [1,2]. It is divided into 2 types, namely primary and secondary AP. Based on classification, secondary AP is more often and occurs when the embryo grows in the abdominal cavity after it is expulsed from the ruptured fallopian tube or primary seat [4]. AP has a wide range of signs and symptoms due to implantation site variability [5]. These include nausea, vomiting, vaginal bleeding, abdominal pain until acute abdomen, and shock. Some patients might be asymptomatic [6] where the abdomen enlarges as normal intrauterine pregnancy [3,[7], [8], [9]]. Similar symptoms were met in this case, where patient had no related complaints and was found normal on routine obstetric examination.

Due to the rarity and the variety of symptoms of AP, diagnosis is often challenging. Based on Green-top Guideline no 21, ultrasound (US) has diagnosis criteria to define AP [10]. US should find the absence of an intrauterine gestational sac and a dilated tube with a complex adnexal mass, a gestational cavity surrounded by loops of bowel separated by peritoneum, and a wide mobility similar to the fluctuation of the sac. In this context, US becomes the diagnostic tool for AP [3,[7], [8], [9]] but cannot be the only reliable modality for AP. This is because half of the AP cases are missed [4] by US diagnosis due to limited ability such as operator dependence and incomplete penetration, particularly in advanced pregnancy. US also has limited ability to image the detail of placenta and uterine wall [3,[7], [8], [9]].

With the excellent ability to image the detail of soft tissue, MRI is only an alternative and adjunct diagnostic tool for AP [3,4,10]. It is shown when there is a suspicious US finding of AP [3]. MRI has multiplanar and multiparameter imaging, superior resolution for soft tissue, and zero radiation. Furthermore, MRI is excellent for preoperative planning because of the ability to image the exact anatomical condition of the fetus, placenta, the affected intraabdominal organ, the detail of placental invasion, and the vascular.

For pregnancy evaluation, T2-weighted image often becomes the preferred sequence. In normal pregnancy, amniotic fluid will show low and high signals on T1-weighted and T2-weighted image, respectively. The placenta will show a moderately hyperintense structure [11], serving as another method to evaluate image. T2-weighted with fast imaging sequence as FIESTA [7], HASTE and balanced-steady state are selected because of their relatively resistant to artifacts of maternal and fetal motion. There is also a proper indication of fetal anatomy with the ability to differentiate between the placental tissue and underlying myometrium [12]. Based on this sequence and method, the uterine wall has a 3-layered appearance consisting of a high-signal-intensity vascular layer between 2 thinner low-signal-intensity layers.

Despite the significance of MRI, there was not any presurgical imaging in this case study. Therefore, patient who received an abdominal MRI after the emergency fetal evacuation found the AP to evaluate the retained placenta. During surgery, the placenta was left in situ to avoid bleeding and other consequences, as retained placenta on MRI would show hyperintensity on T1-weighted and T2-weighted image. The attachment site of placenta in the myometrium was thinner than the opposite [13].

MRI results of this case showed that there were iso-to-hyperintense lesions on the superoanterior aspect of uterus in T2-weighted image as the retained placenta and air component, indicating the connection between the lesions and the vagina. There were also uterine defects on the anterior of the uterine wall and fibrous tissue around these lesions. Although the visualization of uterus and adnexa prepregnancy was not available, the fibrous tissue around uterine defect on postsurgical MRI showed the possible scenario. Patient had cesarean surgery and laparotomy due to AP histories before the third pregnancy. The uterine scar lacked decidua basalis or contained damaged fibrinoid degeneration [14]. Therefore, the pregnancy was possible to implant into a fibroid scar and not surrounded by good quality endometrium, becoming complicated with uterine rupture [14] shown on MRI as uterine defect.

The management of AP includes medical which uses methotrexate in early cases and surgical operation [10]. Moreover, laparoscopic is the standard for ectopic pregnancy [15], which is considered a safe and effective option due to reduced operative time, blood loss, and length of hospital stay [10]. Despite the significant benefits, laparotomy is still considered in the advanced AP with maternal and fetal high morbidity and mortality, showing the need for surgical methods related to the management of placenta whether left in situ or otherwise. This is because the removal has bleeding risk but the retention is associated with ileus, bowel obstruction, fistula formation, hemorrhage, and peritonitis [10].

A good report of MRI is needed for the surgical operation. The report should contain [3]:

• 1.Fetus: the presence of intraabdominal extrauterine fetus, the position and the relation of the uterus and maternal abdominal organs, also the viability of the fetus
• 2.Placenta: the implantation site and extension, the placental blood supply and the presence of placental bleeding or infarction
• 3.Amniotic sac: amniotic fluid volume, membrane rupture signs, and amniotic fluid leakage if presence
• 4.Uterus: cervix integrity, uterine wall, endometrial cavity, uterine rupture signs, and exit point of the fetus
• 5.Intra-abdominal fluid
• 6.Any maternal pathology if presence

When the possible scenario of this case occurred as shown by the imaging during the second and the third pregnancy, early diagnosis should be performed using sonography combined with doppler flow imaging followed by confirmation of pelvic MRI. The thickness of anterior myometrial should be evaluated in terms of management method. When postsurgical treatment is needed, the process includes laparotomy to remove the scar and re-suture to reduce the recurrence. The radiologist should answer the clinician's need for the exact border and vascular activity of the retained placenta and also the adhesion to the bowel. In this case, T2-weighted image showed hypointense lesion covering the retained placenta and had hyperintense omentum as a clear border between the lesion and omentum. There was also no flow void, showing the absence of feeding vascular to the placenta. There was a small part of adhesion to the bowel that was explored slice-to-slice (Fig. 3).

Fig. 3.

Axial view of T2-weighted image MRI showed that a small part of the lesion had adhesion (yellow circle) to the bowel (yellow star) (the left picture was lower than the right one).

Conclusion

In conclusion, this study showed that MRI had an excellent ability to explore the details of AP. This case suggested including the MRI as an evaluation modality for advanced AP, particularly that related to uterine defects and previous history.

Patient consent

Written informed consent was obtained from the patient for this case report publication and accompanying images.