unruptured ectopic pregnancy ultrasound?

Ectopic pregnancy

Ectopic pregnancy refers to the implantation of a fertilised ovum outside of the uterine cavity.
Epidemiology

The overall incidence has increased over the last few decades and is currently thought to affect 1-2% of pregnancies. The risk is as high as 18% for first trimester pregnancies with bleeding 15. There is an increased incidence associated with in-vitro fertilisation pregnancies.
Clinical presentation

The classic presentation is with abdominal pain and bleeding. In practice, the symptoms are not necessarily severe - often there may be only mild pelvic pain and spotting in early pregnancy (5-9 weeks of amenorrhea 5). Nonetheless, monitoring of hemodynamic status is crucial, as hemorrhage can be life-threatening.
Complications

Complications somewhat depend on the type of ectopic. General complications for a typical (tubal) ectopic pregnancy include:

tubal rupture: 15-20%

Pathology
Locations

In the vast majority of cases, the ectopic implantation site is within a Fallopian tube.

tubal ectopic: 93-97%
ampullary ectopic: most common ~70% of tubal ectopics and ~65% of all ectopics
isthmal ectopic: ~12% of tubal ectopics and ~11% of all ectopics
fimbrial ectopic: ~11% of tubal ectopics and ~10% of all ectopics
interstitial ectopic/cornual ectopic: 3-4%; also essentially a type of tubal ectopic
ovarian ectopic: ovarian pregnancy; 0.5-1%
cervical ectopic: cervical pregnancy; rare <1%
scar ectopic: site of previous Cesarian section scar; rare
abdominal ectopic: rare ~1.4%

Risk factors

in vitro fertilisation
prior ectopic pregnancy
tubal injury or surgery, including tubal ligation
pelvic inflammatory disease
salpingitis isthmica nodosa
endometrial injury
intrauterine contraceptive devices 5
endometriosis 16
previous placenta previa 16
congenital uterine anomalies 16
smoking 17
past history of spontaneous or induced abortions 17
maternal age (advanced maternal age increases the risk of ectopic pregnancy)19
history of subfertility 20

Markers

Serum beta HCG levels tend to increase at a slower rate. Whereas a normal doubling rate in early pregnancy is approximately 48 hours, an increase of 50% or less in 48 hours is strongly suggestive of a non-viable (either intra- or extrauterine) pregnancy 11. Rarely the urinary and/or serum b-HCG will be negative despite an ectopic pregnancy 13.

Serum progesterone levels are generally lower in a non-viable (including ectopic) pregnancy 6; progesterone of 5 ng/ml or less is strongly associated with pregnancy failure, whereas in a viable pregnancy, progesterone is usually 20 ng/ml or more 5. Clearly, there is a significant grey zone. Furthermore, serum progesterone levels may take days to process. Progesterone is therefore not included in standard protocols for managing the suspected ectopic pregnancy.
Radiographic features

It is useful to know a quantitative beta HCG prior to scanning as this will guide what you expect to see. At levels <2000 IU, a normal early pregnancy may not be visible.

The most reliable sign of ectopic pregnancy is the visualization of an extra-uterine gestation, but this is not seen in 15-35% of ectopic pregnancies 3.
Ultrasound

The ultrasound exam should be performed both transabdominal and transvaginally. The transabdominal component provides a wider overview of the abdomen, whereas a transvaginal scan is important for diagnostic sensitivity.

Positive sonographic findings include:

uterus
an empty uterine cavity or no evidence of an intrauterine pregnancy
an exception to this is a rare heterotopic pregnancy
pseudogestational sac or decidual cyst: may be seen in 10-20% of ectopic pregnancies
current evidence suggests that one should not initiate treatment for ectopic pregnancy in a haemodynamically stable woman on the basis of a single hCG value 11
decidual cast
thick echogenic endometrium
tube and ovary
simple adnexal cyst: 10% chance of an ectopic
complex extra-adnexal cyst/mass: 95% chance of a tubal ectopic (if no IUP)
an intra-adnexal cyst/mass is more likely to be a corpus luteum
solid hyperechoic mass is possible but non-specific
tubal ring sign
95% chance of a tubal ectopic if seen
described in 49% of ectopics and in 68% of unruptured ectopics
ring of fire sign: can be seen on color Doppler in a tubal ectopic, but can also be seen in a corpus luteum
an absence of color Doppler flow does not exclude an ectopic
live extrauterine pregnancy (i.e. extra-uterine fetal cardiac activity): 100% specific, but only seen in a minority of cases
peritoneal cavity
free pelvic fluid or hemoperitoneum in the pouch of Douglas
the presence of free intraperitoneal fluid in the context of a positive beta HCG and the empty uterus is
~70% specific for an ectopic pregnancy 4
~63% sensitive for ectopic pregnancy 4
not specific for ruptured ectopic (seen in 37% of intact tubal ectopics)
free fluid in the hepatorenal recess
interrogation of the right upper quadrant for free fluid reduces time to diagnosis 21
free fluid in Morison's pouch in the context of an ectopic pregnancy is highly suggestive that operative management will be necessary 20
live pregnancy: 100% specific, but only seen in a minority of cases

In patients receiving in vitro fertilisation (IVF), it is important not to be completely reassured by the presence of a live intrauterine pregnancy 8, as there is a possibility of a coexisting ectopic pregnancy in ~1-3:100 17 (i.e. heterotopic pregnancy). In patients not receiving IVF, the risk of heterotopic pregnancy is minuscule (1:30,000).
Treatment and prognosis

Management depends on the location of the ectopic pregnancy and the patient's hemodynamic status. In general, the options are:

surgical: (in the case of tubal ectopics with open or laparoscopic salpingectomy or salpingotomy)
medical
methotrexate (a folate antagonist) either administered systemically or by direct ultrasound-guided injection
relative contraindications to methotrexate include 12:
rupture
mass >3.5 cm
fetal cardiac activity
bHCG >6000-15,000 mIU/mL
the gestational mass can paradoxically increase in size following methotrexate on subsequent scanning and does not necessarily imply failure of methotrexate therapy 3
potassium chloride (via ultrasound-guided direct injection only)
conservative or expectant management is being recognized as an option for those ectopics where rupture has not occurred (i.e. no hemoperitoneum) and fetal demise has already taken place

Complications

lithopedion: may result with larger ectopic pregnancies which have been left in situ

Differential diagnosis

The differential diagnosis of abdominal pain in a pregnant patient is broad. An ectopic pregnancy must be excluded by ultrasound. Other common diagnoses in this setting include:

ruptured corpus luteum
exophytic corpus luteum of pregnancy
intrauterine pregnancy
incidental adnexal mass
appendicitis (negative beta-hCG)

The scenario of clinically suspected ectopic pregnancy that is not confirmed on ultrasound, is referred to as a pregnancy of unknown location, with the alternative possibilities being of very early pregnancy or a completed miscarriage.