Contributed by
Children's Healthcare of Atlanta/Emory University
Amy Mehollin-Ray, and Leann Linam.
History
32-week pregnant mother, referred for MRI for suspected placenta accreta.
Images (Click any image to enlarge)
Question
What obstetric emergency is shown?
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Correct answer
Incarcerated gravid uterus
Discussion
Incarcerated gravid uterus is a rare pregnancy complication where the retroverted uterus, with progressive enlargement during gestation, becomes trapped beneath the sacral promontory. Typically a gravid retroverted uterus will correct its position before 16 weeks, "flipping" into a more "upright" position in the pelvis. If the uterus remains retroverted, progressive fetal growth and resulting uterine enlargement results in the uterine fundus becoming trapped in the pelvis (incarceration), which can lead to additional complications like uterine ischemia, uterine rupture (particularly of the overstretched, "sacculated" lower uterine segment), infection, and intrauterine fetal demise. Small case series suggest a fetal mortality rate of around 33%.
Maternal symptoms are typically related to compression by the uterus on adjacent pelvis structures, with urinary retention, constipation, and low back pain. This patient presented to an outside ER at 16 weeks unable to void, which ultimately required management with intermittent self-catheterization. She also complained of constipation and had a hospitalization in the late 2nd trimester for acute pain, which was thought to be caused by bleeding, possibly from a large pelvix varix. No attempt had been made to perform a manual reduction earlier in pregnancy, and her referral for advanced imaging at the Children's hospital was due to a suspicion of placenta accreta related to two prior cesarean sections. The retroverted uterus, if known, was not part of her referral diagnosis.
Typical ultrasound findings may include difficulty identifying the cervix, or finding a stretched cervix displaced anteriorly and mistaking that for an empty uterus, with the pregnancy mistakenly thought to be abdominal rather than intrauterine. The bladder may also appear stretched and elongated, compressed anteriorly. On MRI, one should note absence of the cervix in its usual location, beneath what initially appears to be the lower uterine segment (actually the fundus!); the stretched, displaced cervix which is now in line with the vagina, rather than orthogonal to it; the displaced bladder (typically above the pubic symphysis); and complications of pelvic compression (gonadal varices, urinary retention, fecal retention).
This pregnancy was additionally complicated by placenta percreta (second image) and was managed operatively with cesarean-hysterectomy at 34 weeks. Bridging vessels to the bladder required cystotomy. The newborn and mother both recovered uneventfully.
Differential diagnosis
Abdominal pregnancy - important to identify the pregnancy as intrauterine in this case, and not mistake the stretched, displaced cervix for an empty uterus
Cervical ectopic pregnancy - in that case, the "empty" uterus will sit above the fetus
Uterine rupture - similar to abdominal pregnancy, confirming that the fetus is in fact in the uterus and the uterine wall is intact is key
References
- https://www.uptodate.com/contents/incarcerated-gravid-uterus
- https://pmc.ncbi.nlm.nih.gov/articles/PMC8924533/
- https://www.ajronline.org/doi/10.2214/AJR.12.9473