Abdominal ectopic pregnancy

Abstract

An ectopic pregnancy (EP) accounts for 1–2% of all pregnancies, of which 90% implant in the fallopian tube. An abdominal ectopic pregnancy (AEP) is defined as an ectopic pregnancy occurring when the gestational sac is implanted in the peritoneal cavity outside the uterine cavity or the fallopian tube. Implantation sites may include the omentum, peritoneum of the pelvic and abdominal cavity, the uterine surface and abdominal organs such as the spleen, intestine, liver and blood vessels. Primary abdominal pregnancy results from fertilisation of the ovum in the abdominal cavity and secondary occurs from an aborted or ruptured tubal pregnancy. It represents a very rare form of an EP, occurring in <1% of cases. At early gestations, it can be challenging to render the diagnosis, and it can be misdiagnosed as a tubal ectopic pregnancy. An AEP diagnosed >20 weeks’ gestation, caused by the implantation of an abnormal placenta, is an important cause of maternal–fetal mortality due to the high risk of a major obstetric haemorrhage and coagulopathy following partial or total placental separation. Management options include surgical therapy (laparoscopy±laparotomy), medical therapy with intramuscular or intralesional methotrexate and/or intracardiac potassium chloride or a combination of medical and surgical management. The authors present the case of a multiparous woman in her early 30s presenting with heavy vaginal bleeding and abdominal pain at 8 weeks’ gestation. Her beta-human chorionic gonadotropin (bHCG) was 5760 IU/L (range: 0–5), consistent with a viable pregnancy. Her transvaginal ultrasound scan suggested an ectopic pregnancy. Laparoscopy confirmed an AEP involving the pelvic lateral sidewall. Her postoperative 48-hour bHCG was 374 IU/L. Due to the rarity of this presentation, a high index of clinical suspicion correlated with the woman’s symptoms; bHCG and ultrasound scan is required to establish the diagnosis to prevent morbidity and mortality.

Background

Abdominal pregnancies have been defined as serosal pregnancies occurring within the peritoneal cavity but excluding those pregnancies that are tubal, ovarian, intraligamentous or the result of a secondary implantation of primary tubal implantation.¹ The majority of abdominal ectopic pregnancies (AEPs) implant in the pelvis. An AEP is the rarest and the most serious type of extrauterine pregnancy. The pouch of Douglas (POD) is the most common location of an AEP followed by the mesosalpinx and omentum. In contrast to tubal ectopic pregnancies (EPs), AEPs may go undetected until an advanced gestational age. The absence of consistent clinical features makes the diagnosis difficult to establish. In 1944, Studdiford¹ defined the criteria used to diagnose a primary abdominal pregnancy. There are multiple risk factors that predispose patients to an EP, including a history of pelvic inflammatory disease, smoking, fallopian tube surgery, previous EP, endometriosis and assisted reproduction techniques. However, only 50% of women with an AEP have any associated risk factors.² An AEP can reach full-term gestation, with a viable fetus and subsequent perinatal survival, however, these are rare cases.³ Surgery is the preferred procedure for an AEP, and the best option is to remove the entire sac including the fetus, membranes and the placenta.

Case presentation

A multiparous woman in her early 30s presented to the Emergency Gynaecology Clinic at 8 weeks’ gestation based on her last menstrual period with heavy vaginal bleeding and severe abdominal pain. She reported a 2-week history of mild vaginal bleeding and a 48-hour history of heavy bleeding with clots. It was a spontaneous conception. She had stopping taking her contraceptive pill 3 months previously. She described early pregnancy symptoms such as nausea and vomiting. Her medical history included asthma and ulcerative colitis. Her obstetrics history included two normal vaginal deliveries at term and a miscarriage at 6 weeks’ gestation. Her gynaecological history included a diagnosis of endometriosis. Her medications included salbutamol inhaler 100 mcg four times per day and sertraline 50 mg at night. She had a regular 28-day menstrual cycle. Her cervical smear was up to date. She did not have a Mirena intrauterine device in situ. Her observations were stable (Sp0₂ 98% on air, respiratory rate of 14, BP 118/75 mm Hg, heart rate 79 beats per minute and temperature of 36.2°C). Physical examination confirmed generalised abdominal tenderness with guarding in the right iliac fossa. Speculum and bimanual palpation confirmed heavy vaginal bleeding. The cervical os was closed. Adnexal fullness was palpable on the right.

Investigations

Her haemoglobin on admission was 144 g/L (range: 115–165 g/L). Her beta-human chorionic gonadotropin (bHCG) was 5760 IU/L (range: 0–5), consistent with a viable pregnancy. A transvaginal ultrasound scan (TV USS) showed an endometrial thickness of 5.6 mm. Both ovaries appeared normal. Towards the midline of the pelvis, a mass was seen measuring 42×38 mm. The mass contained a cyst that appeared to contain an echogenic focus within, measuring 16 mm in diameter (figure 1). The ultrasound findings raised the suspicion of a fetal pole. No fetal cardiac pulsations were seen. The mass appeared to be separate from the ovaries. The appearance raised the suspicion of an EP. There was no obvious free fluid seen in the pelvis. Her repeat bHCG at 48 hours was 4427 IU/L and her repeat TV USS showed a crown-rump length of 16.5 mm (suggesting a gestation of 8+1 weeks) (figure 2). There was no free fluid. Both ovaries were normal. An EP was observed on the right side, measuring 38×27 mm. Her 96-hour bHCG was 3481 IU/L (table 1).

Figure 1.

Transvaginal ultrasound scan showing a lesion measuring 42×38 mm towards the midline of the pelvis. The lesion contained a cyst that appeared to contain an echogenic focus within, measuring 16 mm in diameter.

Figure 2.

Repeat transvaginal ultrasound scan showing a crown-rump length (CRL) of 16.5 mm, suggesting a gestation of 8+1 weeks.

Table 1.

bHCG trend

Hours	bHCG (IU/L)
Baseline	5760
48	4427	Fall of 1333
96	3481	Fall of 946

bHCG, beta-human chorionic gonadotropin.

Differential diagnosis

The clinical symptoms correlated with her sonographic findings and her bHCG suggested an EP. Due to her abdominal pain and raised bHCG she was consented for a diagnostic laparoscopy.

Treatment

A diagnostic laparoscopy was performed. An indwelling urinary catheter was inserted. The cervix appeared normal. An infra-umbilical incision was performed and the Veress needle inserted. Intraperitoneal entry was confirmed with Palmers, hanging drop and pressure tests. The uterus appeared of normal size and was mobile. The fallopian tubes were normal. A mass extending from the POD and right pelvic sidewall in close proximity to the ovary was observed. It measured 4×3 cm in diameter (figures 3 and 4). The upper abdomen and the liver appeared normal. Superficial peritoneal endometriosis was observed. The ectopic pregnancy was separated from the POD and the pelvic lateral sidewall. The ureter was noted. Bipolar diathermy achieved haemostasis. A pelvic drain was inserted. The estimated blood loss was 1.5 L.

Figure 3.

A mass extending from the pouch of Douglas and right pelvic sidewall in close proximity to the ovary was observed. It measured 4×3 cm in diameter.

Figure 4.

A mass was observed extending from the right pelvic sidewall.

Outcome and follow-up

She remained haemodynamically stable. Her haemoglobin 24 hours postoperatively was 134 g/L. Her drain was removed as it contained <50 mL of serosanguineous fluid. Her bHCG 48 hours later was 374 IU/L. Serial monitoring of her bHCG was scheduled until it was negative. Follow-up was scheduled in the Gynaecology Clinic and histology confirmed an EP.

Discussion

An AEP was first reported in 1708 as an autopsy finding.⁴ Due to its rarity, only case reports or small case series exist in the literature. It has an estimated incidence of 1:10 000–25 000 live births.¹ An abdominal pregnancy is the only type of EP that can advance beyond 20 weeks of gestational age. In 1942, Studdiford¹ established three criteria for the diagnosis of a primary abdominal pregnancy (Box 1). Watrowski et al recently expanded the classic Studdiford criteria, following a case of an omental pregnancy invading the peritoneum of the POD.^{5 6} Since 1952, <50 cases of hepatic pregnancy have been described in the literature, with the most frequent site of implantation being the inferior surface of the right lobe.⁷ An AEP can be classified as early or late. An early AEP is one that presents at or before 20 weeks’ gestation and a late AEP presents after 20 weeks’ gestation. An AEP can also be further classified as primary or secondary. Primary abdominal pregnancy occurs when the fertilised ovum implants directly into the peritoneal cavity; it is the less common type. In 1968, Friedrich and Rankin⁸ proposed that to be a true primary AEP, the pregnancy should be <12 weeks’ gestation and the trophoblastic attachments should be related solely to the peritoneal surface. Secondary abdominal pregnancy occurs when the fertilised ovum first implants in the fallopian tube or uterus and then due to fimbrial abortion or rupture of the fallopian tube or uterus, the fetus subsequently develops in the mother’s abdominal cavity. Classification of an AEP although academically interesting is of limited clinical value. Risk factors include fallopian tube injury, pelvic inflammatory disease, endometriosis, multiparity and assisted reproductive techniques. Thirty-seven per cent of cases have a history of a tubal EP and 61% have a fallopian tube factor.³ It has even been reported after bilateral salpingectomy in a patient who underwent in vitro fertilisation (IVF).⁹ Studies have also suggested that the use of cocaine may be a risk factor for an AEP.¹⁰

Box 1. The Studdiford criteria for the diagnosis of a primary peritoneal pregnancy (L Dunphy).

• The presence of normal tubes and ovaries.

• No evidence of a uteroperitoneal fistula.

• A pregnancy exclusively related to the peritoneal surface.

• No evidence of secondary implantation following initial primary tubal nidation.

Several theories on the pathophysiology of an AEP have been postulated but the aetiology remains to be fully elucidated. Berghella and Wolf¹¹ refuted the diagnosis of primary implantation. Paternoster and Santarossa¹² suggested that delayed ovulation occurring close to menses may reverse the fertilised ovum in its tubal course by retrograde menstrual flow. Cavanagh¹³ postulated that fertilisation may occur in the posterior cul-de-sac where sperm is known to accumulate and that an ovum could lay there due to dependent flow of peritoneal fluid. Dmowski et al⁹ and Iwama et al¹⁴ hypothesised that a retroperitoneal AEP may occur due to migration of the embryo along lymphatic channels. Reports have also described an AEP after a hysterectomy. It has been suggested that IVF may predispose to an AEP via uterine perforation at the time of embryo transfer, migration of an oocyte into the abdominal cavity with subsequent abdominal fertilisation by spermatozoa or migration through a micro-fistulous tract through the uterine isthmus.

Early diagnosis is difficult to establish as women may present with a plethora of symptoms or be asymptomatic. There are no pathognomonic symptoms of an AEP that distinguish it from a tubal pregnancy. It may present as diffuse pain accompanied by signs of incipient pregnancy. At an advanced gestation, the woman may present with non-specific symptoms, such as abdominal pain, vaginal bleeding or decreased, absent and painful fetal movements.¹⁵ Nausea, vomiting and an intense persistent desire to defecate may be prominent symptoms, when the pregnancy implants on bowel. A history of irregular bleeding is less frequently reported than in tubal EPs. Fetal movements may also be reported high in the upper abdomen or there may be absent fetal movements. The fetus may be easily palpable and the presentation may be transverse. Speculum and bimanual examination may show a closed and effaced cervix. Oxytocin may also fail to stimulate the gestational mass. The patient may also present with haemodynamic compromise and shock due to rupture of the AEP.

A suboptimal rise in serum bHCG is a useful marker, but it is not sufficient to establish the diagnosis. However, laboratory investigations may reveal excessively elevated alpha-fetoprotein levels. TV USS is the main imaging modality. However, it only has a sensitivity of 50%. Sonographic features include an empty uterus. The classic ultrasound finding is the absence of myometrial tissue between the maternal bladder and the pregnancy.¹⁶ Other sonographic features suggestive of the diagnosis may include poor definition of the placenta, oligohydramnios and an unusual fetal lie (box 2). However, it can be challenging to differentiate it from a tubal EP at an early gestation, especially when it implants in the vicinity of the adnexa. CT and MRI can also be used for further evaluation. MRI is the gold standard for evaluating placental implantation and preoperative planning. However, it is not uncommon to diagnose an AEP for the first time at laparotomy or laparoscopy performed for a tubal EP. Chen’s review of 17 cases showed that the rate of preoperative diagnosis remained low with only 29.41% of cases diagnosed preoperatively.¹⁷ The accuracy of diagnosis increased with an increase in gestational age and the appearance of the fetal heartbeat. The differential diagnosis includes an EP at other locations, an intrauterine pregnancy in a rudimentary horn, placental abruption or uterine rupture. A retroflexed uterus and the presence of a uterine leiomyoma (fibroid) can also make the diagnosis difficult to render. A false-negative diagnosis as an intrauterine pregnancy can occur. A false-positive diagnosis with cervical, intramural, isolated uterine horn and a bicornuate pregnancy can also occur.

Box 2. Sonographic features of an abdominal pregnancy.

• An absence of myometrial tissue between the maternal bladder and the pregnancy, abdominal wall and pregnancy.

• An empty uterus.

• Poor definition of the placenta.

• Oligohydramnios.

• Unusual fetal lie.

There is no established guidance available for the diagnosis and management of an AEP. An AEP can reach full-term gestation, with a viable fetus and subsequent perinatal survival; however, these are exceptional cases.¹⁸ Between the years 2008 and 2013, 38 cases of advanced abdominal pregnancy resulting in a live birth were reported.¹⁹ Twenty-one per cent of neonates had a birth defect such as limb defects, craniofacial and joint abnormalities, for example, talipes equinovarus, as well as central nervous system malformations.²⁰ Due to abnormal placental implantation, cases of advanced AEP carry multiple risks such as haemorrhage, infection, disseminated intravascular coagulation, fistula formation and pre-eclampsia.²¹ Expectant management to gain fetal maturity has been attempted and has been successful in a few cases.³ The conservative approach by Marcellin et al²² carried a pregnancy until 32 weeks uneventfully. Similarly, Beddock et al²³ described a viable fetus at 37 weeks’ gestation without maternal or fetal complications. There are no strong clinical predictors for successful medical therapy and the decision for medical therapy must be individualised based on the distinctive characteristics of each case. Medical management includes methotrexate (local or systemic), local instillation of potassium chloride, hyperosmolar glucose, prostaglandins, danazol, etoposide and mifepristone.²⁴ Medical management is commonly used where potentially life-threatening bleeding is anticipated, such as an AEP involving the liver or the spleen. Primary methotrexate therapy has a high failure rate due to the advanced gestational age at which an AEP is diagnosed. Postoperatively, histology showing evidence of trophoblast proliferation with neovascularisation involving the organ or structure the pregnancy was attached to confirms the diagnosis of an EAP.²³

Angiographic arterial embolisation can be used as first-line treatment of an AEP with the aim of avoiding surgery or by reducing the vascularity of the placenta making surgery safer.²⁵ Selective embolisation of vessels supplying the placenta should be considered to control the haemorrhage postoperatively from the retained placenta. Historically, an AEP was managed surgically. However, in 1993, Balmaceda et al²⁶ reported laparoscopic management of an AEP at 7 weeks’ gestation. Abossolo et al²⁷ also described successful management of a first trimester AEP with significant intraoperative haemorrhage laparoscopically.²⁷ Laparoscopy can be performed at early gestations as removal of the small and less vascular placental tissue is easier. At late gestations, surgery is the main treatment. The entire sac including the fetus, membranes and the placenta should be removed.²⁸ However, termination of pregnancy should also be offered due to the adverse maternal and fetal sequelae. The fetus can be delivered easily; the key issue is how to manage the placenta. Bleeding from the placental site can be a life-threatening complication during laparotomy as an AEP lacks the haemostatic mechanisms exerted by myometrial contractions, therefore, it fails to constrict the placental vasculature. Indeed, a complicated AEP with the placenta feeding off the sacral plexus has also been described.²⁹ There are two options. The placenta can be removed after ligating the placental blood supply. A good separation technique and adequate vascular management should be performed. The second option is to leave the placenta in situ after ligating the umbilical cord.³⁰ However, this option is associated with sepsis, abscess formation, delayed haemorrhage due to retained placental remnants, adhesions, coagulopathy, ongoing pre-eclampsia and failure of lactogenesis. When the placenta remains in situ, two methods of follow-up are available. The first is the use of methotrexate to accelerate tissue absorption. The role of methotrexate to hasten placental resorption is discouraged by most authors due to the risk of infection. The second method is expectant management, which consists of monitoring the bHCG levels and performing an ultrasound scan. Chen et al¹⁷ waited for self-absorption in cases where the placenta was left in situ and followed up the patients for a maximum period of 26 months. It has been suggested that there is a similarity with the intrauterine placenta accreta spectrum cases and an AEP, especially in the management of the placenta.¹⁷ In Honduras in 1956, a case of an AEP with a dead fetus that developed into a lithopedion, derived from the Greek words lithos (stone) and paedion (child), a term used to describe an AEP in which the fetus dies but cannot be reabsorbed by the mother’s body was described.³¹ Ultrasonographic-guided fetocide of a 14.5 weeks’ gestation to prevent further development and initiate the process of natural resorption has been reported.³²

Abdominal pregnancy has a maternal mortality rate between 0.5% and 18%, which is >7 times higher compared with that of other EPs.^{33 34} This is due to the risk of massive haemorrhage from a partially or totally separated placenta at any stage of pregnancy. Its perinatal mortality rate is between 40% and 95%.³⁵ A high index of clinical suspicion and a multi-disciplinary approach is required to prevent adverse maternal and fetal outcomes.

Learning points.

• Abdominal ectopic pregnancies (AEPs) present with a plethora of non-specific symptoms and may go undetected until an advanced gestational age when the patient presents with a history of recurrent abdominal pain, the presence of fetal movements high in the upper abdomen or absence of fetal movements. Clinical manifestations may also include soreness during fetal movements, easily palpable parts of the fetal body and a transverse presentation.

• There are no specific criteria to diagnose an AEP and it may be missed on ultrasound. However, a classic sign on ultrasound scan is the absence of echo signs of myometrium between the mother’s bladder and the fetus. Additional signs may include poor visualisation of the placenta, oligohydramnios and a transverse presentation. MRI is the gold standard for evaluating placental attachment and vascular connections.

• The mainstay of treatment of advanced AEP is surgery, but the optimal approach has not been determined. Management of the placenta remains controversial. Maternal morbidity and mortality is high as AEPs typically implant on highly vascularised surfaces. Separation of the placenta can occur at any gestation and may lead to life-threatening maternal haemorrhage. Maternal and fetal outcomes are determined by haemodynamic status and gestational age at presentation.

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