Ruptured ovarian ectopic pregnancy presenting with an acute abdomen

Abstract

An ectopic pregnancy occurs in 2% of all pregnancies. A primary ovarian ectopic (OP) is a rare entity and occurs in <2% of all ectopic gestations. It may present in those individuals who take ovulatory drugs, use an intrauterine device or have undergone in vitro fertilisation or embryo transfer. Multiparity and a younger age are other recognised risk factors. Diagnosing an OP pregnancy remains a challenge and it may be misdiagnosed as a bleeding luteal cyst, a haemorrhagic ovarian cyst or a tubal pregnancy by ultrasound scan. The diagnosis is often only established at laparoscopy following histopathological examination. A ruptured OP is a potentially life-threatening condition due to its potential for haemorrhage and hemodynamic collapse. Hence, early diagnosis is crucial to prevent serious morbidity and mortality. The authors present the case of a multiparous woman in her late 30s presenting with a seizure and lower abdominal pain at 6 weeks gestation. Her beta human chorionic gonadotropin was >9000 Miu/mL. A transvaginal ultrasound scan showed no evidence of an intrauterine pregnancy. There was free fluid in the pelvis. She was hemodynamically stable. She underwent a diagnostic laparoscopy, which showed hemoperitoneum and a ruptured left OP pregnancy. She underwent a left oophorectomy. Histology confirmed chorionic villi within the ovarian stroma. This case demonstrates the challenges in preoperative diagnosis of a ruptured OP pregnancy and acts as a cautionary reminder that individuals can present with hemodynamic stability. Rarely, as in this case, an OP pregnancy can occur without the presence of risk factors. Despite its rarity, a ruptured OP pregnancy should be considered in the differential diagnosis of women of reproductive age presenting to the emergency department with acute abdominal pain and a positive pregnancy test.

Background

An ectopic pregnancy is the leading cause of maternal death during the first trimester of pregnancy, accounting for 10% of all pregnancy-related deaths.¹ An ovarian pregnancy, a rare form of non-tubal ectopic pregnancy occurs when the gestation sac is implanted, grown and developed in the ovary. It was first described by Saint Maurice in 1682.² Although its pathogenesis remains to be fully elucidated, possible hypothesis include interference with ovum release from the ruptured follicle, fallopian tube malfunction or inflammatory thickening of the tunica albuginea. The majority of cases are diagnosed by the seventh week of pregnancy when the patient develops the classic clinical symptoms of abdominal pain and vaginal bleeding. However, a plethora of common gynaecological disorders can present with the aforementioned symptoms such as a ruptured ovarian cyst, a tubal ectopic pregnancy, spontaneous miscarriage or dysmenorrhoea. Risk factors for an ovarian ectopic (OP) are similar to those for a tubal pregnancy, but use of an intrauterine device (IUD) appears to be disproportionately associated. An IUD prevents uterine implantation but does not provide protection against ovarian implantation.³ Cheng’s multicentre, large sample, case–control study has shown that the risk of an ectopic pregnancy is increased following the failure of most contraceptives used in the current cycle including IUDs (OR of 16.43), oral contraceptive pills (OR 3.02), levonorgestrel emergency contraception (OR 4.75) and female sterilisation (OR 4.73).⁴ An adnexal mass may be present on examination. Preoperative diagnosis is challenging as it shares a similar clinical presentation with a complicated ovarian cyst, a tubal ectopic or a haemorrhaging corpus luteal cyst. Laparoscopy is the gold standard approach. The diagnosis is established using the modified Spiegelberg criteria, confirmation of non-involvement of the fallopian tube and histological evidence of chorionic villi in the ovary.⁵ Most cases terminate with rupture in the first trimester. However, rare cases of an OP resulting in a live neonate have also been described.

Case presentation

A woman in her late 30s presented to the acute medicine unit at 6 weeks gestation by her last menstrual period with a seizure following alcohol withdrawal. Her medical history included anxiety, depression and alcohol dependence. Her surgical history was unremarkable. There was no gynaecological history of intrauterine contraceptive devices, hormonal contraception, fertility treatment or assisted reproductive techniques. She denied a history of pelvic inflammatory disease, endometriosis or previous ectopic pregnancy. She was gravida 6, parous 2 (3 miscarriages at <6 weeks gestation). Her obstetric history included three normal deliveries at term. She had an irregular menstrual cycle. She was a smoker but denied smoking for 3 months prior to conception. She had a history of binge drinking alcohol. Following termination of her seizure with intramuscular (IM) lorazepam, she commenced treatment with chlordiazepoxide and pabrinex. Twenty-four hours following admission, she developed lower abdominal pain and right shoulder tip pain. There was no history of vaginal bleeding. She was hemodynamically stable. Physical examination showed no adnexal excitation or mass. The cervical os was closed. There was no evidence of vaginal bleeding.

Investigations

Laboratory investigations on admission showed electrolyte imbalances (K⁺ 2.8mmol/L, phosphate 0.72 mmol/L and magnesium 0.69 mmol/L), which had been corrected. Her urine pregnancy test- was positive and her beta human chorionic gonadotropin (BHCG) was also elevated at 9,436 indicating a definitive pregnancy (table 1). Her haemoglobin was within normal range at 123 g/L. An arterial blood gas confirmed a metabolic acidosis.

Table 1.

Laboratory investigations on admission showed an electrolyte imbalance and a raised BHCG

Full blood count	Bone profile
Haemoglobin 123 g/L(115-165)	Calcium 2.31 mmol/L (2.20–2.60)
White cell count 12.2×109/L (4–11)	Alkaline phosphatase 39 iu/L (30-150)
Platelets 164×109/L (150–450)	Phosphate 0.72 mmol/L (0.8–1.5)
Mean cell volume 102.5 fL (80–100)
	Liver function tests
Renal function tests	Albumin 44 g/L(35-50)
Sodium 134 mmol/L(133-146)	Alanine transaminase 47 iu/L(10-50)
Potassium 2.8 mmol/L (3.5–5.3)	Total bilirubin 20 umol/L(0–21)
Urea 3.8 mmol/L (2.5–7.8)	Amylase 118 iu/L(0–110)
Creatinine 118 umol/L (50–100)
EGFR 51 mL/min/1.73 m2 (60–150)	Magnesium 0.69 mmol/L(0.7–1.00)
	BHCG 9436 mIU/mL (0–5)

BHCG, beta human chorionic gonadotropin; eGFR, estimated glomerular filtration rate.

An early pregnancy viability scan (transvaginal ultrasound) was performed. There was no evidence of an intrauterine pregnancy. The endometrium appeared regular with an estimated thickness of 9.8 mm. There was extensive free fluid within the pelvis extending to the lower liver margin (figure 1). Hence, evaluation of the adnexa was difficult and the left ovary could not be visualised optimally (figure 2).

Figure 1.

The ultrasound scan showed free fluid in the pelvis.

Figure 2.

Ultrasound scan of the left ovary.

Differential diagnosis

As the adnexa and the left ovary could not be visualised, the diagnosis of an ectopic pregnancy could not be excluded. A haemorrhagic cyst or a bleeding corpus luteal cyst was also considered in the differential diagnosis. Her recent BHCG was 10,141 iu/L (range: 0–5) and a repeat haemoglobin was 77 g/L (range: 115–165), from an admission haemoglobin of 123 g/L. Therefore, the diagnosis of a ruptured ectopic pregnancy was considered most likely. She remained hemodynamically stable.

Treatment

She was transfused two units of packed red blood cells. An indwelling urinary catheter was inserted. She received analgesia and antiemetics.

Outcome and follow-up

She underwent a diagnostic laparoscopy. An infraumbilical incision was performed. Low pressure, high flow pneumoperitoneum was established. Hemoperitoneum was evident. Both fallopian tubes and the right ovary appeared normal. The left ovary showed a ruptured ectopic with active bleeding (figures 3 and 4). Saline wash and suction of the peritoneum was performed. Her BHCG (10, 141 iu/L) and ovarian findings were consistent with a ruptured ovarian pregnancy. As there was no evidence of haemorrhagic infiltration of the suspensory ligament or haematoma formation at the level of the broad ligament, a left oophorectomy was performed using Vyant diathermy. The pedicle was checked for haemostasis. The estimated blood loss was 1.5 L. Her post-transfusion haemoglobin was 97 g/L, therefore, she commenced treatment with oral iron tablets, ferrous sulphate 200 mg two times per day. On histological examination, the left ovary showed surface rupture with haemorrhage measuring 18 mm in maximum dimension. No fetal parts were visualised macroscopically. Thrombus attached to the surface of the ovary contained chorionic villi and the implantation site was identified (figures 5 and 6). There was no evidence of trophoblastic disease. Her recovery was uneventful. The remaining ovarian tissue should help preserve normal fertility.

Figure 3.

Diagnostic laparoscopy showed hemoperitoneum.

Figure 4.

Diagnostic laparoscopy showed a left ovarian ectopic pregnancy.

Figure 5.

Histopathological examination confirmed the presence of chorionic villi.

Figure 6.

Chorionic villi were noted confirming the diagnosis of a ruptured ovarian ectopic pregnancy.

Discussion

An ectopic pregnancy occurs in up to 2% of all pregnancies.⁶ Indeed, it is among the leading cause of maternal morbidity and mortality. Approximately, 98% of ectopic pregnancies are located in the fallopian tubes, with 70% occurring in the ampulla. Primary OP pregnancy is the implantation of the gestation sac in the ovary. A secondary OP occurs if fertilisation takes place in the tube with posterior regurgitation of the conceptus back to the ovarian stroma.⁷ An OP pregnancy is a rare occurrence with an estimated incidence of 0.5%–3% of all ectopic pregnancies.⁸ The first case was described by St. Maurice in 1682.² The mean gestational age at diagnosis is 7 weeks.⁹ Ninety-one per cent of cases of OP are diagnosed and managed in the first trimester due to frequent ovarian rupture, 5.4% continue into the second trimester and 3.7% will reach the third trimester.¹⁰ The risk factors for developing an OP include the use of an IUD such as the mirena coil, a history of tubal surgery, a previous ectopic pregnancy, endometriosis, pelvic inflammatory disease or ovarian hyperstimulation during assisted reproductive technology.¹¹ In vitro fertilisation is associated with 28.5% of OP, thus supporting the idea of trans-tubal reflux of the fertilised oocyte into the ovary.¹²

Its aetiology remains to be fully elucidated, but it appears to be secondary to reflux of the fertilised oocyte to the ovary.¹³ Interference in the release of the ovum from the ruptured follicle, malfunctioning of the fallopian tubes and inflammatory thickening of the ovarian tunica albuginea have also been suggested. Its pathogenesis includes fertilisation occurring outside of the fallopian tube, followed by implantation within the ovary. The surface of the ovary is covered by tunica albuginea. It lacks muscle fibres. Loose connective tissue and blood vessels are found inside the ovary. Therefore, early rupture may occur.

An OP may present with a history of amenorrhoea, abdominal pain, vaginal bleeding and a positive pregnancy test. Chronic pelvic pain frequently occurs. Individuals may present with hypovolaemic shock secondary to an acute intra-abdominal haemorrhage, although women may be hemodynamically stable, as in this case. A ruptured ectopic may present with dizziness, syncope or hemorrhagic shock. Speculum and bimanual examination may reveal an adnexal mass.

Despite advances in modern sonography, a ruptured OP is still difficult to diagnose on preoperative ultrasound scan. Indeed, the diagnosis of an OP is only established preoperatively in between 5.3% and 25% of cases.¹⁴ Ultrasonography may show a wide hyperechoic ring or mass formed by gestational trophocytes infiltrating into the surrounding tissues, which is greater than the echogenicity of a normal ovary and corpus luteum.¹⁵ Other findings may include a complex adnexal mass with or without fluid in the pouch of Douglas and ovarian enlargement. It is difficult to differentiate between a ruptured OP, a ruptured tubal pregnancy, a haemorrhagic corpus luteum or a chocolate cyst due to the similar ultrasonographic appearances. Terzić et al have suggested that a ruptured OP sonographically is confused with a ruptured corpus luteum in 75% of cases.¹⁶

Surgery remains the mainstay of treatment with minimal access surgery the preferred option. Spiegelberg described criteria for establishing the diagnosis intraoperatively (box 1).^{5 17} The aim of surgery is to remove the ectopic pregnancy, while preserving as much ovarian tissue as possible, especially in women of reproductive age.¹⁸ Wedge resection and oophorectomy are commonly preferred.

Box 1. -Spiegelberg's criteria for intraoperative diagnosis.¹⁷.

• An intact ipsilateral tube, clearly separate from the ovary.

• Gestational sac occupying the normal position of the ovary.

• Gestational sac connected to the uterus by the utero-ovarian ligament.

• Ovarian tissue in the wall of the gestation sac.

There remains a paucity of reported cases regarding medical management of an OP using methotrexate (MTX), probably because an OP is diagnosed acutely when surgical management remains the gold standard. The first case successfully treated with MTX was described by Kudo et al, followed by Shamma and Schwartz who used a single IM injection.^{19 20} Mittal was the first to report an MTX injection directly into the gestational sac.²¹ It has a high treatment failure rate and there is a risk of ovarian bleeding.²² There are also cases reporting OPs resulting in full term pregnancies. Huang reported the case of a woman presenting at 36 weeks gestation diagnosed with an OP. She gave birth to a live infant following a laparotomy.²³ Sehgal described an undiagnosed OP during an elective caesarean section.²⁴ Patel et al also presented a rare case of a twin ovarian pregnancy diagnosed by ultrasound.²⁵ These cases demonstrate the potential for an OP to grow until the later stages of pregnancy with devastating consequences if rupture occurs. Recurrence of an OP has been described involving the contralateral ovary.²⁶ A successful intrauterine pregnancy has been described by Koo et al in 46.4% of women following an OP.¹⁴ 10.7% were diagnosed with a tubal pregnancy and only 3% were diagnosed with secondary infertility.¹⁴

This case highlights the diagnostic challenges in women of reproductive age presenting to the emergency department with acute abdominal pain and a positive pregnancy test. A high index of clinical suspicion is required to establish the diagnosis of an OP and indeed, the diagnosis is rarely established preoperatively.

Learning points.

• The diagnosis is challenging due to its non-specific clinical presentation. It may be misdiagnosed as a haemorrhagic ovarian cyst, a bleeding corpus luteum or a tubal ectopic pregnancy. The sonographic appearances may be hampered by the presence of a haematocele and hemoperitoneum. Individuals may also be hemodynamically stable.

• Laparoscopy remains the gold standard for management. The Spiegelberg criteria is used to establish the diagnosis intraoperatively.

• Early diagnosis is crucial to preserve fertility, avoid an emergency laparotomy and improve clinical outcomes.

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