A rare case report of amniocele in pregnancy: Utility of magnetic resonance imaging in solving the puzzle

INTRODUCTION

An amniocele refers to the herniation of the amniotic sac through a defect in the uterine myometrium. It often arises as a consequence of intrauterine procedures such as suction evacuation, dilatation, and curettage; manual removal of the placenta; or other procedures involving the uterus. While amnioceles are often asymptomatic, they carry a potential risk of uterine rupture, which can lead to acute, life-threatening complications for both the mother and fetus. With the increasing trend of pregnancy in women of advanced maternal age, alongside a rise in the number of pregnancies following myomectomy, the incidence of amniocele has been observed to be on the rise. Retained placenta, a leading cause of postpartum hemorrhage, occurs in approximately 1 in 100–1 in 300 births.^[1] Instruments such as cervical dilators, curettes, and uterine sounds are commonly implicated in uterine perforation, with the relatively avascular fundus being the most frequently perforated region.^[2]

CASE REPORT

A 25-year-old G₂P₁L₀ woman presented to the labor room at 30 weeks of gestation, with a 3-day history of lower abdominal pain and reduced fetal movement. She described the pain as dull, intermittent, and localized mainly to the lower abdomen. There were no accompanying symptoms of fever, vomiting, or vaginal bleeding. Her obstetric history was significant for a stillbirth at 10 weeks of gestation, which was complicated by retained placenta, requiring instrumentation and manual removal in a secondary health institution.

An emergency obstetric ultrasound was performed, which revealed a cystic lesion in relation to the uterine wall at the point of tenderness, with the fetal coccygeal region protruding through this lesion [Figure 1]. Initially, a sacrococcygeal cystic teratoma was suspected. However, upon further assessment, it was noted that myometrium was absent at the site of the cystic lesion, raising suspicion of a myometrial defect with herniation of the amniotic cavity and fetal coccyx. To confirm the findings, a magnetic resonance imaging (MRI) was performed, which demonstrated the herniation of the amniotic sac through the myometrial defect [Figure 1].

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Figure 1:

(a) Abdominal USG revealed a cystic lesion (*) within the lower abdomen, along the uterine fundus with the presence of fetal coccygeal (white arrow). The lesion shows an area of fluid level (black arrow), likely representing hemorrhage. (b) Axial T2-weighted MRI shows herniated amniotic sac (*) through myometrium containing fetal coccyx (white arrow). (c) T1-weighted axial MRI shows show outpouching (white arrow), the area marked (*) demonstrates T1 hypointense signal intensity, likely fluid. (d) Sagittal SSFP confirms the outpouching of the sac (*).

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The estimated fetal weight was 1.8 kg at the time of presentation. The patient’s blood pressure was 120/70 mmHg, and her pulse rate was within normal limits. Due to the recent developments, an emergency cesarean section was performed, resulting in the delivery of a very low birth weight male neonate through a low transverse uterine incision. The neonate was alive at birth, with an appearance, pulse, grimace, activity, and respiration (APGAR) score of 8 at 1 min and 8 at 5 min. The infant was immediately admitted to the special care baby unit.

Post-delivery, the myometrial defect was repaired [Figure 2], and the low transverse incision was closed in layers. The patient was hemodynamically stable and was discharged on post-operative day 7. Follow-up visits were uneventful, with satisfactory recovery.

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Figure 2:

Surgical photograph of the patient showing a 4 × 5 cm fundal uterine defect.

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DISCUSSION

Amniocele is a defect in the uterine wall, often diagnosed incidentally during pregnancy or in the postpartum period and can present with a range of clinical manifestations. Patients may experience abdominal pain, discomfort, or a palpable mass. The differential diagnosis for lower abdominal pain includes conditions such as ovarian cysts, ectopic pregnancy, adnexal torsion, and uterine abnormalities.^[3,4] A herniated amniotic sac into the abdominal cavity is strongly suggestive of impending uterine rupture.^[5,6] However, uterine rupture does not always occur immediately after sonographic detection of amniotic sac extrusion.

In cases where the amniotic sac has herniated, all patients in the expectant group underwent a cesarean section before full term due to worsening abdominal pain, abnormal fetal heart rate patterns, or the onset of labor. Despite these complications, all mothers delivered healthy babies. In the current case, delivery of the fetus was successfully deferred until 30 weeks. This suggests that conservative management options may be viable in cases with a herniated amniotic sac that presents with silent uterine rupture.

The optimal management approach for cases with a herniated amniotic sac remains undefined, especially in the first and early second trimesters. Management will depend on factors such as gestational age, severity of abdominal pain, and fetal condition. If the fetus is mature enough to survive outside the uterus, cesarean delivery should be performed. In cases where the patient is asymptomatic or experiences only temporary abdominal pain without fetal distress, the impact of the herniated amniotic sac on the pregnancy has not been fully clarified.

It is essential to distinguish between cases that require surgical intervention and those that can be managed expectantly. At present, there are no established methods to predict uterine rupture in such cases. While abdominal pain is a typical symptom of impending uterine rupture, it is not exclusive to cases requiring surgical intervention. In one study, seven of the eight expectant cases presented with abdominal pain at diagnosis, highlighting that the presence of this symptom alone does not preclude the possibility of successful expectant management.

Several studies have suggested that ultrasonographic evaluation of the lower uterine segment near term can predict uterine scar rupture when attempting a vaginal birth after a cesarean section.^[4] However, no cut-off values for myometrial thickness have been established to predict spontaneous uterine rupture in cases of herniated amniotic sacs during pregnancy. MRI provided precise information on the extent of the overstretched amniotic sac, and serial assessment of myometrial thickness was a key to managing the pregnancy expectantly.

In cases of suspected amniocele, imaging modalities such as ultrasound and MRI are crucial for confirming the diagnosis and assessing the extent of the lesion. Management of amniocele is guided by the clinical situation, including the presence of symptoms, risk of complications, and the gestational age. While conservative management is often preferred for stable patients without complications, surgical intervention may be necessary if complications such as rupture or infection arise.

DIFFERENTIAL DIAGNOSIS

Ovarian cyst

Ectopic pregnancy

Adnexal torsion

Uterine anomalies

Placental abruption

Sacrococcygeal teratoma

Amniocele.

CONCLUSION

Amniocele is a rare but potentially serious complication of pregnancy, seen in patients with a history of uterine trauma. Early and accurate diagnosis through ultrasound and MRI can help differentiate it from other pelvic pathologies and will guide appropriate management. Conservative monitoring can be done in select asymptomatic cases, but timely surgical intervention is crucial to prevent worst outcomes like uterine rupture.

TEACHING POINTS

1. Amniocele is herniation of the amniotic sac through a uterine wall defect, often caused by prior uterine trauma (e.g., D&C and myomectomy).

2. Complications include risk of uterine rupture, preterm delivery, and maternal-fetal complications.

3. Ultrasound is the first-line modality for assessment and MRI can help in detailed assessment of myometrial thickness and lesion extent.

MCQs

1. What is the most common cause of amniocele?

   1. Placenta previa

   2. Uterine trauma (e.g., D&C and myomectomy)

   3. Ectopic pregnancy

   4. Ovarian cyst rupture

   Answer Key: b

2. What is the primary risk associated with untreated amniocele?

   1. Placental abruption

   2. Uterine rupture

   3. Pre-eclampsia

   4. Fetal macrosomia

   Answer Key: b

3. What is the most common location of uterine perforation in cases of iatrogenic trauma?

   1. Lower uterine segment

   2. Uterine fundus

   3. Cervical canal

   4. Lateral uterine wall

   Answer Key: b