Successful hysteroscopy and curettage of a caesarean scar ectopic pregnancy

Abstract

Caesarean scar ectopic pregnancies are the rarest type of ectopic pregnancy. The optimum management regime is not yet established. We report the case of a 39-year-old woman who presented at 11 weeks gestation with painless vaginal bleeding, having had 2 previous caesarean sections. Ultrasound revealed a gestational sac within the caesarean scar niche. On follow-up, her serial ß human chorionic gonadotropin (ßHCG) measurements fell significantly. The woman initially opted for conservative management but subsequently required surgical management. Hysteroscopy demonstrated a sac within the caesarean scar which was successfully evacuated by ultrasound-guided suction curettage, with no complications. Caesarean scar ectopic pregnancies are becoming increasingly common. Diagnosis is primarily through ultrasound using specified criteria. Management may be conservative, medical or surgical excision depending on the clinical circumstances. Hysteroscopy and suction curettage is an effective therapeutic option for caesarean scar ectopic management.

Background

Caesarean scar ectopic pregnancies (CSEPs) are a rare form of pregnancy where a gestational sac implants into the uterine caesarean scar. The prevalence is increasing with a rising caesarean section rate. Such pregnancies can carry a high risk of maternal morbidity and mortality. Complications include haemorrhage, uterine rupture and hysterectomy. Early and accurate diagnosis is therefore essential in guiding management and preventing severe complications.

Case presentation

A 39-year-old Caucasian woman (Gravida 5 Para 4) presented to the Early Pregnancy Unit (EPU) at 11 weeks gestation complaining of persistent painless vaginal bleeding. She had a history of two normal deliveries and two previous caesarean sections (one emergency caesarean for failed progress in labour and subsequently one elective caesarean). She had no significant medical history. Her last delivery was caesarean section 8 years previous.

At presentation to the EPU, her serum ßHCG was 7324 U/L. She underwent a transvaginal scan, which reported an intrauterine sac with no yolk sac or fetal pole. A repeat ßHCG 48 hours later had fallen to 5620 U/L. An ultrasound scan was scheduled for 7 days later to assess viability of the pregnancy but the patient did not attend this follow-up scan. She presented again 2 weeks later with ongoing painless bleeding. Her serum ßHCG was 371 U/L on this admission.

Investigations

The woman then underwent a repeat transvaginal ultrasound at the EPU. This demonstrated a 21×17 mm gestational sac on the anterior uterine wall, at the level of the caesarean scar, with surrounding vascularity. There was 3.5 mm of myometrial thickness anterior to the sac. The uterine cavity and cervical canal were both empty (figure 1, video 1). These ultrasonographic findings were consistent with a CSEP.

Figure 1.

Longitudinal view of the uterus demonstrating a gestational sac in the caesarean scar on the anterior wall of the uterus. The uterine cavity and cervical canal are empty. Note the thin myometrium anterior to the sac.

Video 1.

Download video file ^{(7.6MB, mp4)}

DOI: 10.1136/bcr-2020-241183.video01

Differential diagnosis

Differential diagnoses which were considered included a low lying intrauterine sac or cervical ectopic pregnancy. Low gestational sacs with accompanying bleeding may sometimes indicate a miscarriage. However, the features on transvaginal ultrasound examination (that of a gestational sac within the anterior uterine wall, thin anterior myometrial thickness and an empty uterine cavity and cervix) made these differential diagnoses less likely.

Treatment

The woman was counselled regarding her management options. As she was experiencing minimal tenderness and had a significant fall in ßHCG since initial presentation, she was offered expectant management with regular EPU review. A repeat transvaginal scan was arranged for 14 days later, which demonstrated a persistent sac within the caesarean scar, now decreased to 14.9×6.8 mm. Her repeat serum ßHCG was decreased to 43 U/L. The patient remained pain free but still complained of persistent light bleeding. Her haemoglobin level remained stable throughout her care. In view of this persistent ectopic and her non-resolving symptoms, the woman underwent an emergency hysteroscopy and suction evacuation of retained products of conception. She was also consented for a laparoscopy if needed.

A hysteroscopy was performed under general anaesthetic. This demonstrated trophoblastic tissue above the internal os on the anterior uterine wall. Transabdominal ultrasound confirmed a 15 mm gestational sac at the level of the caesarean scar, at the interface of the anterior uterine wall and the bladder. Suction evacuation was gently performed using a size 8 hegar suction curette, under continuous abdominal ultrasound guidance. A transvaginal ultrasound was performed after suction of the sac which confirmed the uterine cavity was empty. The procedure was uncomplicated with no uterine perforation or ongoing haemorrhage. There was blood loss of 100 mL. Additional haemostatic measures such as balloon tamponade were not required. There was no indication for recourse to laparoscopic or hysteroscopic excision given the uncomplicated nature of the procedure.

Outcome and follow-up

The woman was discharged the next postoperative day and she made an uneventful recovery. Histopathological evaluation of the evacuated tissue confirmed hyalinised chorionic villi consistent with products of conception. One week later, she performed a negative urine pregnancy test. The patient was well at 3-month follow-up.

Discussion

CESPs are a rare form ectopic pregnancy which was first described in 1978.¹ It has a prevalence of 1:2000 pregnancies. This rate is increasing, which likely reflects the global increasing rate of caesarean sections and probable improved ultrasonographic diagnosis.^2–4 The mechanism of scar ectopic formation is poorly understood but is suggested to be caused by invasion by the implanting blastocyst through a microscopic tract that develops from the trauma of a previous caesarean.^5–7 Implantation can occur into scarring of the uterus from any previous uterine procedure such as ERPC (evacuation of retained products of conception), hysterotomy and especially caesarean section with consequential embryonic implantation in the myometrium.⁸ Intramural implantation following In vitro fertilisation (IVF) embryo transfer has also been suggested.⁶ There is no known correlation between the number of caesareans a woman has had and risk of CESP.

Two types of caesarean scar ectopic have been recognised.^{5 8} Endogenic ectopic pregnancies (type 1) grow towards the uterine cavity. Such pregnancies can progress to full term but carry a high risk of uterine rupture and haemorrhage. Exogenic ectopics (type 2) grow outwards towards the uterine serosa surface and carry a more ominous prognosis with a higher risk of severe complications.^{6 8 9}

Presentation

Women can typically present with abdominal pelvic pain and bleeding in early pregnancy. Up to 40% of women can be asymptomatic.^{2 3 6} Less commonly, patients may also present with uterine rupture and haemodynamic instability.

Differentials diagnosis

The diagnosis of CSEP can be challenging. The presence of a low gestational sac may be mistaken for a low intrauterine sac or a cervical ectopic pregnancy. In a review of 751 cases, 13.6% of cases were misdiagnosed. Misdiagnosis is frequently reported.^{5 10 11} In our described case, the pregnancy was initially deemed to be intrauterine by an experienced senior operator, thus reiterating the diagnostic difficult which CESP can present. The early recognition of caesarean scar ectopic is imperative for guiding the most appropriate treatment, prevention of maternal complications and to optimise fertility preservation.^{7 12}

Imaging

Transabdominal and transvaginal ultrasound is the first-line investigation for CSEP and is largely universally available. High accuracy rates have been reported.^{5 6} Transabdominal ultrasound allows panoramic view of the uterus and bladder, which is beneficial at later gestations where a good panoramic view may not be achieved with a transvaginal approach.⁵

Specific ultrasound criteria for diagnosis have been suggested^{5 6}:

• Empty uterine cavity and a closed and empty cervical canal.

• Gestational sac embedded in the caesarean section incision scar.

• A triangular/round or oval‐shaped gestational sac that fills the niche of the scar.

• A thin or absent myometrial layer between the gestational sac and the bladder.

• Evidence of functional trophoblastic/placental circulation on colour flow Doppler examination.

• Negative ‘sliding organs’ sign.

MRI is a diagnostic adjunct which can demonstrate the location of the gestational sac and its relationship with adjacent organs and degree of myometrial invasion and possibility of bladder involvement.⁷ This modality is useful for follow-up or for complicated cases such as women in later gestation or fibroid uteri.

In our described case, our transvaginal ultrasound findings were that of a gestational sac within the caesarean niche, negative sliding sign and an empty uterus and cervical canal, representative of a CSEP.

Management

The optimum management of CSEP is undetermined.^{2 8 9} Over 30 treatment regimens have been described.^{9 10} Comprehensive patient counselling is imperative. Management should be individualised according to each clinical circumstance with the prevention of severe complications and fertility preservation as the primary consideration.⁹ Other determinants include the size and morphology of the ectopic, fetal viability and haemodynamic instability.¹²

Expectant management can be considered for haemodynamically stable patients. Where the pregnancy is non-viable, this option confers a minimal risk of uterine rupture and hysterectomy although requiring close patient follow-up.^{12 13} Birch Petersen et al report successful treatment in 42% with a complication rate of 51%.⁹ Conversely, in the presence of fetal cardiac activity, expectant management carries significant risk of fetal loss, placenta praevia, adherent placenta, haemorrhage and hysterectomy.5 11 13–15 Harb et al report a live-birth rate of 56% in women who choose to continue a viable pregnancy expectantly.¹¹

Medical management includes systemic or local injection with methotrexate or embryocides. Systemic methotrexate management carries a significant risk of failure and risk of ongoing need for surgery such as retained products of conception (RPOC).2 9 11 12 A systematic review demonstrated that 25% of women undergoing systemic methotrexate management required further treatment.⁹ Advantages of systemic methotrexate include avoidance of surgery and preservation of fertility.¹⁶ Disadvantages include longer follow-up compared with surgery, potential treatment failure and methotrexate toxicity.¹⁷

Methotrexate can be administered locally into the gestational sac. This may overcome the reduced systemic methotrexate absorption by the fibrous caesarean scar tissue and maintain contact with the target tissue whilst limiting systemic methotrexate exposure.^{17 18} This technique is suitable for haemodynamically stable patients who are pain-free, a gestation age less than 8 weeks, absence of fetal cardiac activity and hCG <5000 IU/L.⁹ A care series of 11 patients undergoing local methotrexate injection demonstrated was successful in 83%.¹⁸ Local administration appears to resolve pregnancies more quickly and has fewer side effects compared with systemic methotrexate.¹⁹ Disadvantages include a longer follow-up period and requirement for analgesia. Potassium chloride can be used in combination with local methotrexate, as a more effective embryocide which may reduce the risk of haemorrhage.^{17 20 21}

Surgical evacuation of the pregnancy is associated with high rates of success and low complication rate.^{2 9 11} A study of 191 women who underwent ultrasound-guided suction curettage demonstrated low rates of hysterectomy, uterine perforation and blood transfusion.² However, the reduced contractility within the myometrial defect may predispose to haemorrhage.^{11 22} ‘Blind’ procedures without ultrasound guidance are associated with higher risk of complications.⁹ Other described techniques include uterine evacuation under laparoscopic visualisation.²² Additional haemostatic approaches such as shirodkhar suture and foley catheter tamponade following curettage can be considered where further haemostasis is required.^{2 4 11}

Hysteroscopic resection enables transvaginal removal of tissue under direct observation with electrocoagulation haemostasis. The scar integrity and surrounding vascularity can be directly assessed. Hysteroscopy can be used in combination with systemic methotrexate or following uterine artery embolisation. There is significant risk of haemorrhage with this approach, as a consequence of defective contractions in the myometrium and uterine cervix.¹² Hysteroscopy and laparoscopy can be combined, especially with CSEP which are exogenous.⁵

Laparoscopic or open resection of the ectopic pregnancy allows direct visualisation of the pregnancy and removal of the scar and is therefore suggested to be preferable in type 2 CESP.⁸ Laparoscopic approaches are associated with lower risk of bleeding compared with open excision.⁹ High success rates and low risk of major complications are associated with laparoscopic excision of CESP.^{9 23}

Novel techniques such as high intensity-focused ultrasound followed by suction curettage have been described with high success rates.^{9 24 25}

In this described case, there was significant drop in ßHCG over the course of woman’s treatment. The woman remained symptomatically stable with minimal bleeding over a period of expectant observation. However, she later opted for definitive surgical treatment, having undergone 2 weeks of follow-up with no discernible resolution of her symptoms. Her family was complete and she did not seek any future pregnancies. In view of this, she opted for hysteroscopy with suction curettage. Alternative therapeutic approaches such as post-hysteroscopy laparoscopic excision were not required in this instance because of successful suction evacuation.

Recurrence and prognosis

Future pregnancies carry an inherent risk of recurrent scar implantation. However, recurrence of CSEP is reportedly low at 3.2%–5%.^{3 5} Complications which can arise include increased risk of uterine rupture and placenta accreta, which may have life-threatening consequences. However, successful pregnancy after CSEP is well reported and the majority of women will have a normal pregnancy following CSEP.³

Conclusion

CSEPs are becoming increasingly common. Early diagnosis is important for planning further management and for prevention of major complications. Treatment must be individualised according to the woman’s clinical circumstances. The optimal management strategy has not been yet identified. This case demonstrates that hysteroscopy and ultrasound-guided curettage can be used as an effective treatment modality.

Learning points.

• Caesarean scar ectopic pregnancies are the rarest type of ectopic pregnancy.

• Caesarean scar ectopic pregnancy should be considered in all women who have had a previous caesarean section or uterine surgery.

• Severe complications include uterine rupture, haemorrhage and hysterectomy.

• Hysteroscopy and suction curettage can be effective as a management strategy.