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Department of Fetal Medicine and Obstetric & Gynecological Ultrasound, Manipal Hospital, Bangalore, Karnataka, India
10.1 Ectopic Pregnancy
An ectopic pregnancy is a pregnancy located outside the normal endometrial cavity. A variety of ectopic pregnancies are possible based on the location. These include tubal (most common – about 95 % of all ectopic pregnancies), interstitial, cornual, cervical, ovarian, scar, intra-abdominal, intra-myometrial and heterotopic pregnancies.
Ectopic pregnancy is more often seen in patients with a history of infertility, PID and a previous ectopic pregnancy. The incidence of ectopic pregnancy is on the rise on account of increasing in-vitro fertilisation (IVF) conceptions. Clinical features include amenorrhoea, a positive pregnancy test (or high serum beta hCG), spotting, abdominal pain and even hypovolemic shock.
Ultrasound is considered the modality of choice for diagnosis of ectopic pregnancy.
Ultrasound Features of an Ectopic Pregnancy (Fig. 10.1)
The absence of an intrauterine gestational sac in the endometrial cavity (especially with a serum beta hCG value of more than 1000 mIU/mL), increases the likelihood of an ectopic pregnancy.
The tissue of an ectopic pregnancy on ultrasound appears as a central cystic area (the gestational sac) surrounded by thick hyperechoic trophoblastic tissue, showing peripheral flow on Doppler. This is pathognomonic for an ectopic pregnancy but often cannot be demonstrated on ultrasound.
The gestational sac may or may not show a yolk sac and fetal pole.
On enlarging the image, on 2D greyscale, low-velocity flows within the trophoblastic tissue are often seen and often useful in confirming the diagnosis.
In cases with ectopic pregnancies, the endometrium may show fluid collection, giving it the appearance of a gestational sac termed ‘pseudo-gestational sac’. The differences between a true gestational sac and a ‘pseudo-gestational sac’ are discussed in Chap. 14.
The endometrium undergoes decidualisation, and in a patient with an ectopic pregnancy. It can appear thick and may show multiple tiny cystic spaces (closer to the endomyometrial junction), which should not be mistaken for a tiny gestational sac.
Fig. 10.1
Findings in a case of an ectopic pregnancy. (a) Echogenic endometrium with a few tiny cystic spaces suggestive of decidualised endometrium. Endometrial cavity showing no evidence of intrauterine pregnancy. (b) Ovaries showing a corpus luteum in the right ovary. (c) Ectopic pregnancy mass showing a central cystic area (i.e., the gestational sac) surrounded by a thick hyperechoic trophoblastic tissue, showing peripheral flow on Doppler. Yolk sac is seen within the gestational sac. This is pathognomonic of an ectopic pregnancy, but is not always seen. (d) Turbid-free fluid suggestive of blood is seen in the peritoneal cavity
Other than ‘pseudo-gestational sac’ and cysts in a decidualised endometrium, the differential diagnosis for an ectopic pregnancy includes a complete abortion and corpus luteal haemorrhage (discussed in Chap. 14).
Transabdominal scan is very useful in picking up an ectopic pregnancy because it pushes all the extra-pelvic structures (that could mimic or shadow a small ectopic pregnancy mass) out of the pelvis. This helps locate the site of any mass, even a small adnexal mass, and one is less likely to miss an ectopic pregnancy mass. Also, it helps to know exactly where to look for the ectopic pregnancy mass at the transvaginal scan that follows the transabdominal scan.
Diagnosis of an ectopic pregnancy is very important because they may present with acute pain and there is potential for rupture and intraperitoneal haemorrhage. The management of ectopic pregnancies other than tubal ectopic pregnancies is difficult, with intramuscular or local methotrexate and local potassium chloride being resorted to in some cases, depending upon the location of the ectopic pregnancy and its viability. Local administration of these agents is done under ultrasound guidance. The management of ruptured non-tubal ectopic pregnancies is even more challenging.
10.1.1 Tubal Ectopic Pregnancy
This is the commonest type of ectopic pregnancy. The appearance on ultrasound varies depending upon how advanced the gestation is, and whether there is any associated bleeding from the lesion.
Ultrasound Features of Tubal Ectopic Pregnancy (Figs. 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8 and 10.9)
The absence of an intrauterine pregnancy.
The tubal ectopic pregnancy mass is seen as an extra-ovarian adnexal mass. It may be seen just adjacent to the ovary. The ‘sliding sign’ can be used to ascertain its extra-ovarian origin.
Typically, it is a circumscribed mass, within which there is usually a gestational sac (seen as a central cystic space) showing thick hyperechoic trophoblastic tissue surrounding it.
Within the gestational sac, one may or may not see a yolk sac and a fetal pole. The fetal pole will show pulsations if it is a live ectopic pregnancy. The presence of a yolk sac, a fetal pole or a fetal heart pulsation helps in making a confident diagnosis of an ectopic pregnancy.
The trophoblastic tissue shows high peripheral vascularity (high-velocity, low-resistance flow), often termed ‘ring-of-fire’.
Ovaries appear normal with a corpus luteum. Most often, the corpus luteum is seen in the ipsilateral ovary but rarely, may be seen on the contralateral side. A corpus luteum can appear a little similar to an ectopic pregnancy, as it is circumscribed and may have a central cystic area.
Doppler flows are of limited value in distinguishing an ectopic pregnancy from a corpus luteum. What helps in differentiating the two is the thick echogenic margins that surround the gestational sac of an ectopic pregnancy mass and its extra-ovarian location.
Ectopic pregnancy masses are typically tender to touch.
Sometimes the ectopic pregnancy mass may not be as well circumscribed or well defined as mentioned above, because of haemorrhage from the ectopic pregnancy resulting in a hematosalpinx. The hematosalpinx appears as an elongated tortuous heterogeneous mass seen in the adnexa often beside the ovary. At times, the ectopic gestational mass may be seen within the hematosalpinx.
Haemorrhage from a ruptured tubal ectopic pregnancy or a tubal abortion could result in blood and clots surrounding the ectopic pregnancy mass forming a complex, heterogeneous (i.e., with hypoechoic and hyperechoic areas) avascular mass. If bleeding has been massive, the entire ovary, ectopic pregnancy mass, etc., might all be lying within a huge pelvic clot, and the tissue of the ectopic pregnancy may be difficult to identify on ultrasound, within the mass.
In an ectopic pregnancy, the fluid in the pelvis is typically turbid (suggesting it is blood) due to tubal rupture. Sometimes the haemoperitoneum is massive, and blood and clots may be seen outside the pelvis, in the paracolic gutters and Morisson’s pouch.
An important differential diagnosis for a ruptured tubal ectopic pregnancy is a corpus luteal haemorrhage (discussed in Chap. 14). What helps distinguish the two is the absence of a well-defined extra-ovarian adnexal mass and a negative urine pregnancy test or normal levels of serum beta hCG, in the latter.
Fig. 10.2
Case of tubal ectopic pregnancy (a) Extra-ovarian adnexal mass is seen just adjacent to the ovary. (b) The ectopic pregnancy mass shows a central cystic area (the gestational sac) surrounded by thick hyperechoic trophoblastic tissue
Fig. 10.3
Ectopic tubal pregnancies. (a) Case 1 – gestational sac showing yolk sac and a fetal pole. (b) Image showing tracing of fetal heart pulsation. (c) Case 2 – large fetal pole with fetal heart pulsation
Fig. 10.4
Live tubal ectopic pregnancy. (a) Flow is seen surrounding the trophoblastic tissue. (b) In addition to peripheral vascularity, flow is seen in the centre of the ectopic pregnancy mass due to fetal heart pulsation. (c) The ovary shows a corpus luteum with a central cystic area and peripheral vascularity. The corpus luteum is, however, intra-ovarian, and does not show hyperechoic thick margins around the central cystic area
Fig. 10.5
Case of tubal ectopic pregnancy with hematosalpinx. (a) Hematosalpinx seen as an elongated tortuous heterogeneous mass just above the right ovary. Ectopic pregnancy tissue is not well visualised within the hematosalpinx. (b) The presence of ectopic pregnancy tissue was confirmed and located within the hematosalpinx, by the presence of flow around a suspicious hyperechoic area (the tissue of the ectopic pregnancy) which was seen on 2D grey scale in the hematosalpinx
Fig. 10.6
Tubal ectopic pregnancy with hematosalpinx. (a) TS and LS view of the hematosalpinx. The hematosalpinx is seen just beside the left ovary. (b) Hematosalpinx seen as the complex mass which can resemble a clot. However, the presence of the flow in the walls of the tubal mass suggested that this is a hematosalpinx with a clot within, rather than an independent clot in the pelvis
Fig. 10.7
Three different cases of ectopic pregnancy seen as a complex heterogeneous pelvic mass-suggestive of clots. (a, b) In all the images, the ectopic pregnancy tissue cannot be seen within the complex masses. (c) Massive clot (line traced across it) is seen in the POD, and in this case neither was the ectopic pregnancy mass, nor the ovary of that side, seen separately on scan
Fig. 10.8
Case of tubal ectopic pregnancy with significant haemoperitoneum. Turbid fluid suggestive of blood is seen in (a) the adnexa surrounding the ectopic pregnancy mass (arrow) and ovary, (b) the POD and (c, d) the general abdominal cavity
Fig. 10.9
Case of a failing tubal ectopic pregnancy with turbulent flow. (a) The ectopic pregnancy is seen just anterior to the left ovary and appears heterogenous because of prominent vessels within the trophoblastic tissue. (b) Turbulent flow with mosaic colour is seen within the trophoblastic tissue, similar to that of an AV malformation. (c) Flow in the trophoblastic tissue shows a low RI of 0.2 (also seen in AV malformations)
10.1.2 Interstitial Ectopic Pregnancy
This is a pregnancy located in the interstitial part of the fallopian tube. This is often wrongly termed as cornual ectopic pregnancy.
Here the tissue of the ectopic pregnancy (i.e., a circumscribed mass with a central cystic space suggestive of a gestational sac, surrounded bythick hyperechoic trophoblastic tissue that shows peripheral vascularity) is seen eccentrically located, just beyond the margins of the endometrial cavity. This is best seen on a 3D rendered coronal image of the uterine cavity.
‘The interstitial line’, a classic ultrasound feature of interstitial ectopic pregnancy, is a thin hyperechoic line seen extending from the superior and the lateral end of the endometrial cavity to the centre of the ectopic pregnancy mass.
The ectopic pregnancy mass is seen surrounded by a thin myometrial rim.
It appears as a mass bulging out at one cornual end of the uterus and moves en masse with the uterus.
Like other ectopic pregnancies, the ectopic pregancy mass may be tender to touch.
At times, a normal intrauterine pregnancy close to the uterine cornua may be wrongly reported as an interstitial ectopic pregnancy, because of the uterine shape (Fig. 10.13). One must be aware of this possibility.
Fig. 10.10
Interstitial ectopic pregnancy. (a) Ectopic pregnancy tissue (long arrow) is visualised just beyond the endometrial margins on greyscale. The image shows the hyperechoic short interstitial line (short arrow) extending between endometrial margins and the ectopic pregnancy mass. The ectopic pregnancy mass is seen as a protrusion from the external surface of the uterus, protruding out at one cornua. (b) 3D pregnancy coronal image showing the ectopic pregnancy mass (arrow), beyond the endometrial margins
Fig. 10.11
Coronal image of two cases of interstitial ectopic pregnancy. (a) Interstitial line (arrow) is seen extending between the endometrial margins and the ectopic pregnancy mass. (b) 3D coronal image showing ectopic pregnancy tissue beyond the endometrial outline
Fig. 10.12
Case of interstitial ectopic pregnancy. (a) Longitudinal section showing the ectopic pregnancy mass beyond the endometrial margins and bulging out of the uterine surface. The mass shows increased vascularity in the trophoblastic tissue. (b) Transverse section showing the ectopic pregnancy tissue and the uterine body. (c) Coronal image shows the ectopic pregnancy mass bulging out of the cornual end of the uterus. The ectopic mass is seen outside the endometrial margins. Thin myometrial tissue (arrows) is seen surrounding the ectopic pregnancy tissue. (d) Inj. methotrexate was administered locally for management. The needle is seen in situ (arrow) in the image
Fig. 10.13
Case of twin pregnancy (arrows) in a patient with an arcuate uterus. The upper sac was wrongly interpreted as a case of interstitial pregnancy. The gestational sac was, however, clearly seen within the endometrial margins (outlined) ruling out an interstitial pregnancy
10.1.3 Cornual Ectopic Pregnancy
This is pregnancy occurring in a non-communicating rudimentary horn of a uterus with a congenital anomaly. The pregnancy in these cases may extend for a longer duration, and is often picked up at rupture which causes severe pain and haemorrhage.
Here, the pregnancy is seen in one horn of a bicornuate uterus, i.e. the non-communicating horn. It is important to demonstrate the lack of continuity between the endometrial cavity of the pregnant horn and the cervical canal below it.
In cases of rupture (trophoblastic invasion of the entire wall), turbid fluid suggestive of blood may be seen in the pelvis.
Fig. 10.14
Cornual ectopic pregnancy in a patient with a left-sided unicornuate uterus and a right-sided non-communicating rudimentary horn. (a) TS of the pelvis on TAS showing both horns of the uterus. The right gravid horn shows increased vascularity. (b) Longitudinal section showing the vascular pedicle of the non-communicating gravid horn connecting it to the main uterine body. (c) Ectopic pregnancy tissue is seen in the rudimentary horn which shows thick trophoblastic tissue (arrows). (d) Transverse section of the uterus on TVS showing the vascular pedicle connecting the rudimentary horn to the left unicornuate uterus. (e) Non-gravid, left-sided unicornuate uterus showing an empty endometrial cavity
Fig. 10.15
Cornual ectopic pregnancy in a patient with 17 weeks of gestation who presented with acute abdominal pain. (a) Fetus (FET) in the non-communicating gravid horn above the uterus. (b) Non-canalised pedicle connecting the gravid horn to the main uterine body. This is important to demonstrate, in order to diagnose a cornual ectopic pregnancy wherein the cavity of the rudimentary horn does not communicate with the main uterine body posing a potential threat for rupture. This patient had been scanned earlier with a diagnosis of pregnancy in one horn of a bicornuate uterus and the ‘non-communication’ had been missed. (c) Turbid fluid seen below the pedicle suggestive of rupture of the gravid horn. (d) Rudimentary horn seen at surgery. 500 mL of blood was drained from the abdominal cavity and the rudimentary horn was excised
10.1.4 Ovarian Ectopic Pregnancy
Ovarian ectopic pregnancies are rare, constituting 0.5–1 % of all ectopic pregnancies.
The tissue of the ectopic pregnancy (i.e., the gestational sac ± yolk sac or fetal pole, surrounded by thick echogenic trophoblastic tissue showing Doppler flow around it) is seen surrounded by hypoechoic ovarian tissue.
The corpus luteum may or may not be visualised in the same ovary.
The trophoblastic tissue in most ovarian ectopic pregnancies is thicker and may not be well circumscribed. On enlarging the image on 2D greyscale, low-velocity flow within the trophoblastic tissue is seen and is useful in diagnosis. These flows are best picked up on power Doppler (or HD Doppler) and may be missed on regular colour Doppler, because of their low velocities.
A tough differential diagnosis for an ovarian ectopic pregnancy is a corpus luteum. Conventionally, serum beta hCG values should be more than 1000 mIU/mL to confirm diagnosis.
Fig. 10.16
A case of ovarian ectopic pregnancy. (a) The ovary is enlarged and shows a poorly defined circumscribed hyperechoic area suggestive of trophoblastic tissue (between arrows). Within this, a tiny cystic area suggestive of a gestational sac is seen. A small yolk sac is seen within. Ovarian tissue is seen around the ectopic pregnancy tissue. (b) Minimal peripheral flows seen on power Doppler around the trophoblastic tissue. A corpus luteum (CL) is seen just beside the ectopic pregnancy tissue in the same ovary. Beta hCG in this case was 2600 mIU/mL
Fig. 10.17
A case of ovarian ectopic pregnancy. Patient had a laparoscopy done for a right tubal ectopic pregnancy. The tube was found to be normal and was apparently ‘cleaned up’. In view of rising beta hCG and discomfort experienced by the patient, a scan was repeated, which revealed an ovarian ectopic pregnancy. (a) Thick trophoblastic tissue surrounding a central cystic space suggestive of a GS. (b) Flow was seen around the trophoblastic tissue on HD Doppler. (c) Turbid fluid suggestive of blood was seen in the POD, suggesting haemorrhage from the ectopic pregnancy. Beta hCG at the time of the scan was 4713 mIU/mL
10.1.5 Cervical Ectopic Pregnancy
This form of ectopic pregnancy is often missed because typically on ultrasound examination, one first examines the endometrial cavity followed by the adnexa, and the cervix is often forgotten.
An empty endometrial cavity.
‘Hourglass’ shaped uterus with a barrel-shaped or ballooned-out cervix.
The entire tissue of the ectopic pregnancy (i.e., the gestational sac ± yolk sac or fetal pole, surrounded by thick echogenic trophoblastic tissue showing Doppler flow around it) is seen in the cervix below the level of the internal os, that is, below the level at which the uterine arteries are seen entering the uterus (on TS).
An important differential diagnosis for a cervical ectopic pregnancy is incomplete or inevitable abortion (Figs. 10.20 and 10.21). The points that help differentiate the two are:
The presence of peri-trophoblastic flow within the cervix and fetal heart pulsations, if present, help to confirm a cervical ectopic pregnancy.
An open internal os, a dead embryo and a flattened GS are suggestive of an incomplete or inevitable abortion.
Previous scan images showing an intrauterine gestation also help in diagnosing an incomplete or inevitable abortion.
Cases of cervical ectopic pregnancy that are managed with standard evacuation and curettage often present with massive bleeding that may be difficult to control.
Fig. 10.18
Cervical ectopic pregnancy. Patient presented with spotting and a positive pregnancy test. (a) ‘Hourglass’-shaped uterus noted, with a ballooned-out cervix. The cervix appeared heterogeneous and hyperechoic. Endometrial cavity was empty. (b) No significant flow seen on Doppler in the cervix. (c) On 3D Doppler, multiplanar sectional views revealed that the entire complex mass was below the level of the closed internal os (i.e. the level at which the uterine arteries (arrows) approach the uterus transversely, seen in the image on the right). The internal os was closed, which helped in making a diagnosis of a cervical ectopic pregnancy
Fig. 10.19
Live cervical ectopic pregnancy. (a) Ballooned-out cervix with the ectopic pregnancy mass, within, that showed a central cystic area with vascular trophoblastic tissue surrounding it. (b) Fetal pole and yolk sac are seen within. (c) Fetal heart pulsations detected on Doppler
Fig. 10.20
(a) Inevitable abortion with pregnancy sac seen in the cervical canal and the internal os (arrow) was open. (b) In this case, no flow was seen in the trophoblastic tissue. The above findings suggested that this was a case of inevitable abortion
Fig. 10.21
Patient presented with heavy bleeding. (a) Ectopic pregnancy mass seen in the cervix with thick trophoblastic tissue and a central, irregular cystic space suggestive of a gestational sac. (b) TAS- the uterine body appeared normal and the cervix was ballooned out, showing trophoblastic tissue within. (c) Scanned image of the patient’s previous report (done elsewhere a few days earlier) which shows a GS in the lower uterine cavity and a normal-appearing cervix. (d) On careful examination, it was seen that there was a thick vascular channel supplying the trophoblastic tissue from the posterior wall of the uterus at the midcorpus. From the image of the previous scan, it was easy to confirm that though this appeared like a cervical ectopic pregnancy, it was a case of inevitable abortion and was easily managed with surgical evacuation. (e) Vascular pedicle (small arrows) of the trophoblastic mass seen on greyscale and Doppler from the posterior myometrium, with the endometrium anterior to it (long arrow) appearing normal
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