Incidentally-discovered calcified pelvic mass during workup for low back pain in a 56-year old woman. The patient recalled abnormal obstetric history 30 years ago. Otherwise, there was no relevant clinical or lab abnormality. CT scan clearly shows an extra-uterine calcified fetal skeleton on MPCR (multi-planar curved reformat) images.

A lithopedion (litho = stone; pedion = child), or stone baby, is a rare phenomenon which occurs most commonly when a fetus dies during an ectopic pregnancy. If the dead fetus is too large to be re-absorbed by the mother’s body it becomes a foreign body to the mother’s immune system. To protect itself from possible infection, the mother’s body will encase the fetus in a calciferous substance. The fetus is gradually mummified becoming a stone baby. Lithopedions
may occur from 14 weeks’ gestation to full term. It is not unusual for a stone baby to remain undiagnosed for decades and found incidentally when taking plain films for various reasons (like this case).

1. Wikipedia
2. Chang, et al. Lithopedion case report Chinese Medical Journal (Taipei) 2001;64:369-372

Credit: Dr Ahmed Haroun