An incarcerated uterus or trapped uterus describes an uncommon situation where a retroverted or retroflexed gravid uterus fails to ascend into the abdominal cavity.
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Epidemiology
This is an uncommon presentation and is said to occur in 1 in 3000 pregnancies 1. Uncomplicated retroversion may be seen in as many as 9% of pregnancies 2.
Clinical presentation
diffuse pain
in the first trimester may result in transient urinary retention
rectal pressure or constipation
Pathology
Entrapment of a portion of a gravid retroverted uterus. As the gravid uterus increases in size, it may get caught at the sacral promontory, bending the gravid retroverted uterus.
Associated with posterior or fundal fibroids, endometriosis, uterine structural abnormalities such as didelphic or a bicornuate uterus, previous gynecologic surgery resulting in adhesions, and a spectrum of abnormal placental villous adherence. The incarcerated uterus is prone to uterine rupture.
Associations
Radiographic features
Ultrasound
cervix may be difficult to identify
cervix is anterior and superior to the gravid uterus
the fetus is positioned deep within the cul-de-sac
the maternal urinary bladder is malpositioned and lies anterior, rather than inferior to the products of conception
the lower uterine segment is displaced anteriorly giving an appearance of a myometrium with central cavity between the urinary bladder and the fetus and may be mistaken for an ectopic or an abdominal pregnancy
History and etymology
The first case of incarceration of the gravid uterus was described by William Hunter in 1754.
Differential diagnosis
On imaging consider
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