Fetus in feto: a case study with explanation

A 13-year-old boy was operated (exploratory laparotomy) for unexplained pain in the abdomen, and a live fetus wasfound attached to the left kidney. It was explained to be a case of identical twins. In twins, the placental capillariesanastomose very intricately so that one fetus may draw more blood resulting in deprivation of blood supply to theother fetus who may end up with no supply later. It did not kill the deprived fetus, but made it remain arrested inthe erstwhile embryonic stage. While remaining in extraperitoneal space, the deprived fetus is joined by herniatedintestines of the healthy fetus in the physiological hernia. Later, when the intestines return to the abdominal cavity(by creating extra space in the abdomen) of the healthy fetus, the stunted fetus accompanies the intestines andmanages to reach the abdominal cavity of the healthy baby.