Medical mystery: Hong Kong girl born with 'absorbed' siblings' organs inside her

Doctors in Hong Kong discovered that what they believed to be growths inside a three-week-old girl was actually her absorbed twin siblings, ABC News reported.

The unusual case, dating back to 2010, was detailed in the Hong Kong Medical Journal earlier this month. Each of the two structures found in the girl contained intestines, an umbilical cord, a rib cage, a spine, and "primitive" brain matter. They are believed to have grown to between 8 and 10 weeks before being absorbed into the girl's body.

The British newspaper the Mirror reported that the girl underwent successful surgery to have the two masses removed from between her left kidney and her liver.

The case is believed to be the first documented instance of foetus in foetu, as her condition is formally known, in Hong Kong. It occurs in one of every 500,000 births worldwide.

"It was almost impossible to detect during the prenatal check-up, as the embryo inside the baby was too small," a local gynecology and obstetrics specialist, Yu Kai-man, told the Mirror. "Since it is impossible for the little girl to have conceived the pregnancy on her own, the fertilisation of the twin fetuses, of course, belongs to her parents, which has gone to the wrong place."

The report did not state a direct cause for the girl's condition, but at one point the World Health Organization reportedly misidentified it as a form of cancer. Kai-man also suggested that it might be connected to multiple abortions done by the girl's mother.

"The widespread use of antenatal ultrasound in early gestation may provide more concrete evidence, and shed light on this intriguing condition," he said.