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OB ultrasound

33 studies11 challenges

Where is the pregnancy, how old is it, is it well: the questions each image answers, in the order the clinic asks them. Every image opens with how to read it; switch to Practice when you are ready to be tested.

Transvaginal ultrasound across the uterus showing two separate endometrial cavities, with a small gestational sac in the right oneTransvaginal, coronal · 4 to 5 weeks (sac 5.7 mm)

OB ultrasound · Uterine anomalies

Early pregnancy, unusual uterine outline

Diagnosis

Bicornuate uterus with an early pregnancy in the right horn

Normal against abnormal

The plane, and which way is up

Transvaginal in coronal or three-dimensional reconstruction: the outer fundal contour and the shape of the cavity are read together, best in the secretory phase when the endometrium is bright.

Look for, in order

  1. The outer fundus: a normal convex or flat contour, or a deep notch?
  2. The cavity: one, two, or a septum dividing it; how far the division reaches toward the cervix.
  3. Two cervices or two vaginas; the kidneys, which share an origin and are often abnormal too.

What normal looks like

A single fundus with a convex contour and a triangular cavity. A septate uterus has a normal outer contour with a divided cavity; a bicornuate uterus has a fundal notch over 1 cm; didelphys is two separate horns and usually two cervices.

Trap. Septate and bicornuate look alike on a two-dimensional scan and are managed differently; the outer fundal contour, not the cavity, separates them.

Describe it in this order

  1. The plane and the approach (transabdominal or transvaginal)
  2. Location of the pregnancy: in the uterus or not
  3. Number: singleton or multiple, and chorionicity
  4. Viability: cardiac activity
  5. Dating or growth: the measurement that fits the stage
  6. Fetal anatomy, placenta, cord, fluid, cervix, as the stage allows
  7. Adnexa and free fluid
  8. Then, and only then, the impression

Findings

  • Two separate endometrial cavities ('horns')
  • A 5.7 mm gestational sac in the right horn

What it means for the patient

A bicornuate uterus has a deep fundal indentation and two horns; a septate uterus has a normal outer contour with a septum inside. The distinction matters because a septum can be resected and a bicornuate uterus is not operated on. Pregnancy in a horn carries a higher risk of miscarriage, preterm birth and malpresentation.

Framework: Cunningham et al., Williams Obstetrics, 26th edition (maternal physiology, labour mechanics, placental anatomy) (2022).

OBGynSpace Tutor

It coaches the description; it does not read the image for you and will not name the diagnosis before you commit.