History:

 A 28-year-old female presents with mild lower abdominal pain and early pregnancy. She has a history of irregular menstrual cycles and is referred for ultrasound evaluation to assess the pregnancy.

Ultrasound Findings and Description:

●     Uterus with a viable pregnancy in the right uterine horn. The gestational sac contains a 7-week-old fetus with a crown-rump length (CRL) of 10 mm.

●     The non-communicating left rudimentary horn contains a pseudo sac, which measures 2.5 cm. No viable fetal pole or yolk sac is seen within the pseudo sac.

●     The collection in the rudimentary horn is likely blood products surrounding the pseudo sac.

●     Left ovary is normal in size and appearance.

●     The sliding sign is positive, indicating the rudimentary horn moves independently of the left ovary.

●     No free fluid in the pelvis.

Diagnosis:

Early intrauterine pregnancy in the right horn with a pseudo sac in the Non-communicating left rudimentary horn.

Differential Diagnosis:

1. Hematometra in Rudimentary Horn: The collection surrounding the pseudo sac could represent accumulated blood (hematometra), often seen in a non-communicating uterine horn.

2. Ectopic Pregnancy: Although unlikely due to the absence of a fetal pole, ectopic pregnancy in the rudimentary horn remains a consideration.

Discussion:

●     In this case, the early pregnancy is located in the right horn of a bicornuate uterus, while the left non-communicating rudimentary horn contains a pseudo sac, a finding commonly mistaken for an ectopic pregnancy.

●      The positive sliding sign supports that the rudimentary horn moves independently of the left ovary.

●     The presence of a pseudo sac without a fetal pole suggests an absence of a viable pregnancy in the left horn.

●     The risk of rupture or complications from the rudimentary horn remains low unless the collection increases significantly.

●     Regular monitoring is recommended, both to ensure the normal progression of the viable pregnancy in the right horn and to assess any changes in the pseudo sac or potential accumulation of fluid in the left horn.