What is your Diagnosis of this Female Patient?

Our patient presents with a history of 5 weeks of amenorrhoea and scanty bleeding per vagina (P/V).

History and Symptoms
This young woman came in for a routine ultrasound examination at 5 weeks of amenorrhoea. She had normal menstrual cycles before the pregnancy and did not have any history of major illness. She had a history of a lower segment c-section (LSCS) during her first pregnancy.

Family History
She has 1 healthy child, who was delivered at full term by LSCS. The mother (the patient) is one of 4 children.

Present Pregnancy
The patient showed a positive pregnancy test. She has a history of occasional bleeding P/V.

Clinical Examination
Her blood pressure was normal (BP: 126/ 80 mm. of Hg); as were all other vital signs. On abdominal examination, she had mild tenderness over the lower pelvis.

Imaging Studies
The patient underwent routine transabdominal and transvaginal ultrasound imaging to study the viability of the pregnancy.

Image 1: Sagittal section of uterus
(images are courtesy of Dr. Nirmali Dutta, MD, UAE)

Click to enlarge full size images

Image 2: Sagittal section of uterus

What are your findings? Add your thoughts to the comment box.

Are you ready for more images and information?

First let’s describe the B-mode ultrasound image. (Image-1) There is an obvious small cystic structure in the anterior wall of the lower uterine segment of the uterus. Can this just be a simple cyst of the uterus? Are we dealing with a Nabothian cyst? That would not be a significant finding.

This patient has a positive pregnancy test.  Is there a gestational sac in the endometrial cavity in the uterine fundus? The answer is No. The uterine cavity is empty; however there is a thickening of the endometrium, more likely a decidual change of the endometrium. The location of the cystic area is not in the cervix but just above it in the lower uterine segment.

Is that cystic lesion a cervical pregnancy?

Observe the 2nd image. There are a few vessels around the cystic lesion. If you look carefully, the cystic lesion is well within the myometrial tissue of the lower uterine segment. More precisely, the cystic structure is in the anterior wall of the lower third of the body of the uterus, just above the cervix. What can cause this sonographic appearance in a pregnant woman with a history of previous LSCS? Furthermore there is a thick echogenic rim around the cystic lesion. This is not in the appearance of a Nabothian cyst.

Shall we have a look at some more images of this case?

Image 3: Transvaginal sagittal section image of the uterus

Can this lesion be a gestational sac? Note the lesion is located well outside the region of the cervix, as well as clearly inside the anterior wall of the uterus in the lower segment. Observing further, one can see a small hyperechoic line extending from the sac to the endometrial lining.

Can this lesion be an adenomyotic cyst of the uterus? That is indeed a possibility but that does not correlate with the history. The findings are clearly in favor of this being a gestation sac but obviously this is not a cervical pregnancy.

Let’s look closely at the lesion.

Image 4: Close up of the lesion

Can a gestation sac be within the myometrium of the uterus and in the lower uterine segment?

This is not a normal pregnancy.  Let's continue to the discussion and final diagnosis.

Discussion
The only condition that can cause this appearance is the possibility of this being an ectopic pregnancy.

1)  How does this correlate with the fact that this patient has a history of previous LSCS?
2)  Can this pregnancy / sac be somehow related to the LSCS? Are we dealing with a gestation sac in the scar of the previous cesarean section?

The location of the sac in the anterior wall of the uterus is a further clue supporting this possibility. The scar of the LSCS is located in the anterior wall of the lower uterine segment. What is your diagnosis?

Final Diagnosis
Ectopic pregnancy located in LSCS scar – “scar pregnancy” or scar implantation.  Scar pregnancy used to be one of the rarest forms of ectopic gestation. However, the rising use of cesarean sections has resulted in an increased incidence of scar pregnancies in the subsequent pregnancies.

Differentail Diagnosis

1) Aborting gestation sac on its way out of the uterus may present a similar picture. However, an aborting sac would be seen inside the uterine cavity and not inside the myometrial wall. Besides, the embryo in such a sac would be dead and the sac would be oblong with no trophoblastic vascularity around the aborting sac.

2) Cervical pregnancy can also present a similar picture. However the pregnancy would be lower down in the cervix and not within the myometrium.

3) Nabothian cysts can sometimes mimic a scar implantation. However, these are usually thin walled and may be multiple. Nabothian cysts are always located in the cervix.

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References:

References:
1) Images from www.ultrasound-images.com  (see article on scar pregnancy )
2) Callen, Peter. Ultrasonography in Obstetrics and Gynecology
3) Rumack, Carol. Diagnostic Ultrasound
4) G. Tan et al. Scar Pregnancy