An Indian teenager suffering from chronic stomach pains was shocked when doctors told him they were caused by the malformed foetus of his twin.

Doctors found the three-stone mass of bone, hair and teeth inside Narendra Kumar’s abdomen. It measured 20 cms in length and had a trunk of hair that was two metres long.

Dr Rajeev Singh told MailOnline his patient had suffered from bouts of vomiting and lost weight but his family had no idea why.

He said: ‘In the three hour-long surgery, we removed a mass of malformed baby having hair, teeth, a poorly developed head, a bony structure of chest and spine with lots of yellowish amniotic like fluid in the sac.

‘We have witnessed two to three cases like this in India so far,’ the doctor told MailOnline.

The parasite had been feeding off Narendra since his birth after forming an umbilical cord-like structure that leached its twin’s blood supply, MailOnline reports.

He was diagnosed with ‘foetus in fetu,’, a condition which occurs when during the early stages of pregnancy with twins, one foetus enters the other through the umbilical cord.

There, it becomes a parasite, living off its sibling’s body for survival.

Technically, the foetus was alive and was growing due to metabolic activity in Narendra Kumar’s body.’