Acute abdomen or life-threatening heterotopic pregnancy with tubal rupture: where does imaging play a role?

Heterotopic pregnancy (HP) is a rare, potentially life-threatening complication of an intrauterine pregnancy with a simultaneous ectopic pregnancy. There is a higher incidence with assisted reproduction techniques (ART) and radiology can be pivotal in its diagnosis. A 28-year-old woman underwent ART and at 7 weeks’ gestation presented with acute right iliac fossa pain. Transvaginal ultrasound (US) imaging confirmed a viable intrauterine pregnancy. The patients’ pain persisted however, and transabdominal US demonstrated a complex, heterogeneous right adnexal mass. Subsequent magnetic resonance imaging (MRI) confirmed an HP with a ruptured ectopic and haemoperitoneum. Emergency laparoscopic surgery and right salpingo-oopherectomy were performed without complication. We highlight the importance of considering HP as a diagnosis in the acute gravid abdomen, especially when initial investigations have confirmed a viable intrauterine pregnancy. Furthermore, this case highlights MRI as a useful modality in complex cases due to its high soft tissue contrast resolution using non-ionising radiation.

emergency medicine, pregnancy, radiology, obstetrics and gynaecology

Initially described in 1708 as an autopsy finding, heterotopic pregnancy (HP) is a rare, life-threatening multiple pregnancy. It is defined as a viable intrauterine pregnancy (IUP) in addition to ectopic embryo implantation.1 Due to its rarity, clinical signs, symptoms and investigations which can be mistaken for other diagnoses, HP proves a diagnostic challenge. If delayed, there could be disastrous consequences for both the patient and viable IUP. This case highlights HP as an important differential in the acute pregnant abdomen, and demonstrates the role of magnetic resonance imaging (MRI) in investigating the acute abdomen, especially when initial investigations do not fit the clinical picture. Case presentation A 28-year-old Caucasian woman who underwent assisted reproduction techniques (ART) presented at 7 weeks’ gestation (gravida 2, para 0, 1 medical termination of pregnancy) to the emergency department with sudden-onset, severe right iliac fossa (RIF) pain and associated nausea and vomiting. She had a medical history of polycystic ovarian syndrome (PCOS). Her cervical smears were up-to-date and normal. On admission, she was haemodynamically stable and afebrile, and examination revealed a tender RIF, with no vaginal bleeding or masses palpable. Investigations Blood tests The patients’ blood tests showed a raised beta human chorionic gonadotropin (β-hCG), in keeping with a viable uterine pregnancy. She also had a raised white cell and neutrophil count. All other blood tests were unremarkable (table 1). Table 1. | Admission blood | Level | Units | Normal range | | Haemoglobin | 124 | g/L | 130–180 | | Mean corpuscular volume | 97 | fL | 80.0–99.0 | | White cell count | 14.9 | ×109/L | 4.0–11.0 | | Neutrophil | 13.44 | ×109/L | 1.50–7.50 | | Platelet | 160 | ×109/L | 140–400 | | C-reactive protein | <5 | mg/L | 0–10 | | Amylase | 62 | IU/L | 30–110 | | Sodium | 136 | mmol/L | 133–146 | | Potassium | 3.9 | mmol/L | 3.5–5.3 | | Urine | 2.1 | mmol/L | 2.5–7.8 | | Creatinine | 58 | umol/L | 60–120 | | Estimated glomerular filtration rate | >90 | mL/min/1.73m2 | | | Serum beta human chorionic gonadotropin (β-hCG) | 63 001 | IU/L | 7650–229 000 mIU/mL* | The abnormal results are in bold. *Quoted β-hCG reference range is for pregnant women at 7 weeks’ gestation. Radiology An urgent transvaginal ultrasound (TV-US) demonstrated a viable single IUP with a visible yolk sac and crown-rump length of 9.43 mm. An enlarged multicystic right ovary was identified in keeping with the known PCOS, with limited views of the right adnexa. The left ovary was unremarkable. Free fluid was noted within the pouch of Douglas. Appendicitis was the initial working diagnosis given the TV-US findings, and subsequently transabdominal US (TA-US) was performed (figures 1 and 2). The scan was equivocal for appendicitis, but a complex mixed cystic and solid structure was identified adjacent to the right ovary with a moderate volume of surrounding layered, echogenic free fluid, suggestive of haemoperitoneum. An urgent MRI was subsequently performed for further characterisation, which confirmed an HP, peritoneal blood products and a ruptured right ectopic mass (figure 3). Differential diagnosis Given the patient presented with RIF pain and a raised white cell count, appendicitis was considered in the differential. TV-US however could not confidently exclude appendicitis and though the patient was afebrile, which would have been a more atypical presentation of appendicitis, an MRI was performed which led to the diagnosis of HP. After TV-US, MRI is the second-line investigation for suspected appendicitis in pregnancy. A threatened abortion was also considered however was disregarded once the TV-US demonstrated a viable IUP. Another possible differential considered was ovarian torsion, for which US is the imaging modality of choice. Free fluid in the pelvis can be seen in over 80% of cases with key findings of an enlarged ovarian bases mass, often with mixed echogenicity and surrounding peripheral displaced follicles.2 In our case, the mass was demonstrated adjacent to the right ovary, with both ovaries visualised, thus refuting the likelihood of ovarian torsion. Given the patient conceived with ART (clomiphene), ovarian hyperstimulation syndrome (OHSS) was also considered. The incidence of OHSS increases when used with patients who have PCOS.3 Presentations vary from mild abdominal discomfort, nausea and vomiting, to more severe cases of ascites, pleural effusions and intravascular fluid depletion (due to third space fluid accumulation) and gross ovarian enlargement. Typical US, CT and MRI appearances are of bilaterally and symmetrically enlarged ovaries, with multiple cysts and possible ascites and pleural effusions. These were not seen in our case and thus OHSS was less likely. Treatment An emergency laparoscopic surgery (figures 4 and 5) with right salpingo-oopherectomy was performed with no intraoperative or postoperative complications. The patient was successfully discharged home 2 days post-surgery. Outcome and follow-up Histopathology was consistent with ruptured right tubal ectopic pregnancy. At review 1 week post-discharge, the patient was stable and reported no abdominal pain or vaginal bleeding. She went onto receive regular follow-up with the community midwife with open-access to the clinic. The antenatal care for the viable IUP fortunately remained uneventful.

Incidence, risk factors and presentation For spontaneous conception, the incidence of HP is around 1 in 30,000 pregnancies. The incidence rises to approximately 1% with the use of ART.4 With the increased use of ART, the incidence of HP has increased significantly over the last few years and resulted in more acute presentations secondary to ectopic-related complications.5 A literature review of cases similar to ours has previously been published, concurring the fact that HP is increasing with the rise of ART.6 Risk factors include pelvic inflammatory disease, endometriosis, previous tubal surgery and use of an intrauterine contraceptive device (>2 years).7 HP can present similarly to a threatened abortion or ectopic pregnancy, with the onset of symptoms usually around 6–8 weeks’ gestation. Signs and symptoms include abdominal or pelvic pain, vaginal bleeding and a tender adnexal mass with an enlarged uterus on palpation. Over time, complications of HP are ruptured ectopic, haemorrhage and shock, at which point the patient would usually be haemodynamically unstable.8 Our patient was haemodynamically stable, which highlights the wide spectrum of HP rupture presentations. Investigations β-hCG is raised however clinicians can be falsely reassured by this.9 Furthermore, a β-hCG test alone is seldom useful and imaging is used for definitive diagnosis.10 The ectopic pregnancy can mask any β-hCG changes from the viable IUP or vice versa. Guidelines state TV-US is considered the initial imaging modality of choice as it can determine the viability of the IUP and allow some assessment for complications.3 Several cases similar to ours have been published to concur this.11 Pitfalls in TV-US include lack of operator experience, increased body habitus, retroverted uterus or hydrosalpinx which can severely limit full sonographic evaluation for a coexisting adnexal mass. Additionally, patients presenting at an early gestational age may have an HP too small to visualise thus falling below the limits of US resolution. TV-US can also falsely reassure the clinician into considering non-gynaecological diagnoses when a viable pregnancy has been identified, without consideration of a possible concurrent tubal ectopic. The appearance of an ectopic pregnancy on imaging widely varies dependent on gestational age, location, viability and surrounding pelvic pathology. In the early ectopic pregnancy, an adnexal mass (gestational sac) on US will not demonstrate a fetal pole or cardiac activity and may be considered a corpus luteal cyst, especially when an IUP is noted.12 The findings of an extra-adnexal cyst or mass with free fluid on TA-US or TV-US, in addition to an IUP, are highly specific for an ectopic mass. The tubal ‘ring of fire’ sign described as an echogenic and vascular ring on colour Doppler US has a 95% positive predictive value for an unruptured ectopic pregnancy.13 When a large pelvic mass with free fluid is noted, rupture should be considered. Echogenic layering further suggests haemoperitoneum (figure 2). Significance should also be placed on the presence of pelvic free fluid, which should prompt thorough visualisation of both adnexae. A common pitfall in patients using fertility treatments is to attribute the findings of free fluid to ovarian hyperstimulation syndrome.12 The high risk of tubal rupture in ectopic pregnancies highlights the importance of early diagnosis, and consideration of further imaging in complex cases, as seen in our case. Guidelines suggest cross-sectional imaging such as MRI can be a useful adjunct to ultrasonography to characterise HPs3 and as seen in this case, can be key to making the diagnosis and planning the surgical approach, thus significantly impacting patient outcome. Advantages of MRI include the use of non-ionising radiation and superior differentiation of soft tissue and fluid in comparison with CT studies. MRI should not however delay surgical intervention in a clinically unstable patient with a high suspicion of complication of pregnancy.14 An ectopic interstitial mass with haemoperitoneum is almost pathognomic for ectopic rupture15 and clinicians should immediately be alerted to prepare for surgery. Although the majority of ectopic pregnancies occur within the ampulla of the fallopian tube, MRI can also prove useful in describing less common ectopic locations, such as ovarian, interstitial, cervical, peritoneal and even caesarean scar pregnancy. Other gynaecological diagnoses such as haematosalpinx, placental abnormalities, ovarian masses and acute surgical pathology including appendicitis can also be demonstrated. Inclusion of a T1-weighted sequence is recommended as part of the imaging protocol for pregnant patients to identify blood products and haemoperitoneum, which on occasion may be the only findings to suggest an ectopic pregnancy. The wall of the tubal ectopic gestational sac on MRI can present as a cystic structure with a surrounding thick wall of high T2-weighted signal intensity14 and may be accompanied with features of a haematosalpinx or tubal dilatation. MRI gadolinium-based contrast agents should be avoided in patients where a viable IUP is suspected. Management The main aim resides in termination of the ectopic pregnancy while minimising any threat to the viable intrauterine gestation. The gravid uterus should be handled with care during any surgical procedure to avoid uterine irritability and postoperative spontaneous abortion. In cases of haemoperitoneum with patient instability and tubal rupture, laparotomy with salpingectomy is nearly always performed.16 In more stable cases, laparoscopic techniques are preferred. Non-surgical management with focused potassium chloride as an ectopic termination agent has also been reported as a management method with a success rate of approximately 67%.17 Methotrexate is contraindicated in the presence of a viable IUP. Learning points. Heterotopic pregnancy (HP), although a rare entity, is considered a life-threatening emergency. With a delayed diagnosis of ectopic rupture, the consequences for both mother and/or fetus can be fatal. The initial transvaginal ultrasound scan may be falsely reassuring and prevent consideration of HP when a concurrent viable intrauterine pregnancy is detected. The presence of free fluid in the pelvis should trigger thorough visualisation of both adnexae. In cases with diagnostic uncertainty, further imaging with transabdominal ultrasound and MRI should be considered. These have a higher sensitivity of identifying a pelvic ectopic mass and haemoperitoneum, and can exclude other diagnoses for example, appendicitis. Footnotes Contributors: MK obtained consent from the patient, reviewed case notes and obtained notes on surgical outcome and imaging. MK also wrote the first draft of the manuscript. Subsequent drafts were edited by CK and KP. The final draft was reviewed by AS. All authors contributed to and have approved the final manuscript. Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors. Competing interests: None declared. Patient consent for publication: Obtained. Provenance and peer review: Not commissioned; externally peer reviewed.

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