Decidual Cast: Uterine Lining Intact

During a menstrual cycle, the uterine lining usually breaks down and exits the body in smaller fragments mixed with menstrual blood. In rare cases, however, the entire lining sheds at once as a single piece that can resemble the shape of the uterus. This phenomenon is called a decidual cast. It occurs when the lining detaches and passes through the cervix intact rather than breaking apart.

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