Angular pregnancy

TypeAngular pregnancy is a type of pregnancy in which implantation occursthat is located within the endometrial cavity at the lateral upper angle. It is one of the eccentric located pregnancies at the fundal region of the uterus, medial to the insertion of fallopian tube.

Epidemiology:

Rare type of pregnancy carrying high rates of spontaneous abortion, uterine rupture, and placenta accreta.

Pathology:

The embryo is implanted in the lateral angle of the uterine cavity medial to the uterotubal junction and round ligament. In contrast, the interstitial ectopic pregnancy is located in the muscular layer of the fallopian tube and is surrounded by myometrial layer. The critical differentiating feature is that the fertilized ovum of an interstitial pregnancy develops in the uterine wall, whereas in an angular pregnancy, it develops towards the uterine cavity . Anatomically the angular pregnancy is implanted medial to the round ligament.

Radiographic features:

Ultrasound:

- Pregnancy is eccentrically high in location.

- The gestational sac is located within the endometrial cavity at the lateral upper angle.

- On spectrum between normal centrally located and interstitial cornual pregnancies.

- Can mimic interstitial ectopic. 

- 3D ultrasound helpful in precise location of sac.

- Should always have normal myometrial coverage which is thick usually more than 5mm, in contrast to interstitial ectopic where the myometrial covering is thin less than 5 mm..

-  Grows towards the endometrial cavity and requires close follow-up to document gestational sac growing into cavity.

- Given the intrauterine location of angular pregnancies and the enveloping myometrium, these patients are likely to present with symptoms later than patients with ectopic pregnancies.

Treatment and prognosis

Many of these pregnancies result in live birth, but has increased complication rate.

Complications:-

- Spontaneous abortion (38.5%)

- Uterine rupture (13.6%)

- True complication rate not known as cases reported as angular may have actually been interstitial.

Differential Diagnosis:

1- Interstitial ectopic pregnancy: 

- Located in the intramural portion of fallopian tube.  Implantation occurs in the most proximal segment of the fallopian tube where it traverses the uterine musculature.  On the other hand, in the angular pregnancy the  implantation occurs in one of the lateral angles of the uterus, medial to the uterotubal junction and the round ligament of the uterus. This distinction is important because angular pregnancies can be carried to term.

- It is also eccentrically located with respect to endometrial cavity but seen separately > 1 cm from the endometrial cavity.

- Interstitial line sign = an echogenic line in continuity from the ectopic to the endometrial echo complex.

- Covered by myometrium. Myometrium thinned to < 5 mm.

- Can grow to larger size than the tubal ectopic pregnancy.

- Present in settings of an uterine anomaly such as unicornuate, bicornuate, or septate uterus with a rudimentary horn. The gestational sac is located medial to the fallopian tube including the anomalous part,often confused with the interstitial ectopic which is a separate entity.