Doctors in Colombia have discovered a 40-year-old fetus inside an 82-year-old woman who had been complaining about stomach pain.

The woman checked into a Bogota hospital where X-rays revealed the shocking discovery – a dead, decades old, calcified fetus – inside the woman's abdomen.

Doctors believe the woman had a medical phenomonen called a lithopedion, or "stone baby," which occurs most commonly when a fetus from "abdominal pregnancy," which implants outside the uterus, dies and calcifies because it is too large to be absorbed by the body.

According to NTD TV, doctors at Bogota's Tunjuelito Hospital initially thought the woman was suffering either from gastro-enteritis, an infectious form of diarrhea, or gallstones. But on Monday an radiography of her abdomen discovered the fetus.

"This happens because the fetus does not develop in the uterus because it has moved to another place," said Dr. Kemer Ramirez of Tunjuelito Hospital.

The 82-year-old woman will have to undergo surgery to remove the fetus.

According to the Journal of the Royal Society of Medicine, the earliest known case of lithopedion was discovered at the 1582 autopsy of a 68-year-old woman in the French city of Sens. She had carried the fetus for 28 years.