CASE 1
A 32-year-old female presented to the emergency department with per vaginal bleeding, lower abdominal pain and a positive beta HCG. Ultrasound imaging demonstrated a live intrauterine gestation with an estimated gestational age of 8 weeks. A further gestational sac with a live foetus was demonstrated within the left adnexa. A small perigestational haemorrhage was also noted adjacent to the intrauterine gestational sac (Fig 1-2).
A left salpingectomy was performed without complication, and subsequently the intrauterine pregnancy was uneventful with natural delivery of a healthy baby at full term.
CASE 2
A 32-year-old female presented with severe constant left lower abdominal pain, per vaginal spotting and nausea. A pelvic ultrasound was performed at 6 weeks of gestation which demonstrated a viable intrauterine gestation and a small perigestational haematoma. A heterogeneous mass was noted abutting the left ovary. It featured peripheral vascularity but no internal vascularity. There was small volume pelvic free fluid with low level internal echoes consistent with haemoperitoneum (Fig 3-5).
The patient was given a preliminary diagnosis of a haemorrhagic corpus luteal cyst. Heterotopic pregnancy was initially considered but thought less likely. The treating team opted for conservative management with a view to perform short term follow-up ultrasound. Follow-up imaging 2 days later demonstrated a persistent left adnexal mass with interval increase in haemoperitoneum volume. The mass was seen to move separate to the left ovary on transvaginal/abdominal palpation manoeuvres.
Diagnostic laparoscopy was performed on day 3 of presentation and heterotopic pregnancy was confirmed. A left salpingectomy was performed with preservation of the intrauterine pregnancy.
CASE 3
A 19-year-old female presented with suprapubic pain and a positive beta HCG. The initial ultrasound findings demonstrated both an intrauterine pregnancy and non-specific adnexal mass. The intrauterine gestational sac featured both a gestational and yolk sac but no foetal pole. This correlated to an estimated gestational age of 5 weeks and 5 days. A heterogeneous left adnexal structure was demonstrated without internal vascularity. The left ovary was not readily identified. A haemoperitoneum was also present. The differential for the adnexal mass was thought to include a ruptured haemorrhagic cyst along with ovarian torsion and heterotopic pregnancy (Fig 6-8).
The patient decided to have an outpatient surgical termination of the intrauterine pregnancy. A follow-up ultrasound was performed 2 days post termination due to increasing abdominal pain. A round thick walled avascular structure with a central hypoechoic component was seen within the left adnexa. It featured a hyperechoic rim consistent with a tubal ring sign. However, the left ovary was not identified. A moderate volume haemoperitoneum was also seen (Fig 9-10).
Diagnostic laparoscopy was performed, which confirmed a ruptured left tubal ectopic pregnancy with approximately 500 ml of haemoperitoneum and active bleeding. Left salpingectomy was performed and histological confirmation of products of conception was established.
DISCUSSION
Case 1 is a simple case with visualisation of a live tubal ectopic providing easy confirmation of a heterotopic pregnancy. This imaging finding is less common and dependent on the age of gestation. However, with increasing gestational age there is increasing risk of ectopic rupture leading to increased morbidity and mortality (4).
Case 2 and 3 illustrate the concept of availability bias, which results from the clinician or radiologist's interaction with the rarity of a disease entity. One fails to recognise the entities that are rare due to lack of recent experience or knowledge. Furthermore, satisfaction of search of the intrauterine pregnancy adds a further superimposed bias for the reporter and clinician with the temptation to ignore the adnexae (5). These cognitive bias issues lead to a downplaying of the importance of a potential diagnosis or at worst missing the entity entirely.
Differentiating a haemorrhagic corpus luteal cyst from a tubal ectopic pregnancy can be challenging. In early gestation the imaging features can be similar. A tubal ring sign and an adnexal mass that moves independently from the ovary are features highly suspicious for ectopic pregnancy . In addition, haemoperitoneum should raise further suspicion for alternative aetiologies such as a complicated heterotopic pregnancy (6-10).