A pair of conjoined twins have been flown from Bhutan to Australia, where doctors hope they will be able to operate on the 14-month-old girls, who have grown up facing each other, unable to move independently.
Joe Crameri, a doctor at Melbourne Royal Children's Hospital, said staff were examining the twins, Dawa and Nima Pelden, who are joined at the stomach, with the hopes they will be able to carry out of a life-changing operation to separate them.
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"Once we've got that information, then we'll be able to formulate a more correct plan for how we can separate these twins but at the moment we remain confident that we should achieve that in a single operation and we should be able to achieve a good outcome for both twins," Crameri said.
A team of six surgeons and dozens of specialist nurses have been assembled for what is likely to be a lengthy operation on the twins, according to CNN affiliate 9 News.
"All these twins are unique in the way that they're connected. This set of twins are connected predominantly in the abdomen, maybe slightly in the lower part of the chest," Crameri said.
"We know the key areas that we're going to have to focus on are the bowel and the liver. We're hoping that we don't have to deal with any of the structures in their chests and the initial report suggests that we won't have to."
'They're getting cranky'
Funds for the girls' operation was raised by Children First Foundation, a Melbourne-based non profit, and is estimated to cost around $180,000 (250,000 AUD), according to 9 News.
"Mom said the girls are getting a little bit frustrated with each other as you would at 14 months," the charity's CEO Elizabeth Lodge said Tuesday.
"Like any siblings they're getting cranky so mom's really looking forward to the operation happening sooner rather than later."
Born via a caesarean section last year, the girls are believed to be Bhutan's first conjoined twins.
As well as the issues with mobility and comfort, Lodge said the twins had recently been losing weight, which had been a concern to doctors who are now observing them closely.
Several members of the surgical team which will work to separate the Bhutanese girls previously worked on the successful operation to separate conjoined Bangladeshi twins Trishna and Krishna in 2009.
They were separated after a marathon 27-hour surgery, despite doctors initially giving them only a 25% chance of making it.
Conjoined twins occur once every 200,000 live births, according to the University of Maryland Medical Center. About 70% are female, and they are always identical twins.
Scientists believe that conjoined twins develop from a single fertilized egg that fails to separate completely as it divides.
"Although two fetuses will develop from this embryo, they will remain physically connected — most often at the chest, abdomen or pelvis. Conjoined twins may also share one or more internal organs," according to the Mayo Clinic.
"The success of surgery depends on where the twins are joined and how many and which organs are shared, as well as the experience and skill of the surgical team."
They were previously commonly referred to as "Siamese twins," a name which originated with Eng and Chang Bunker, a set of conjoined twins who were born in Siam (now Thailand) in 1811. They lived to age 63 and appeared in traveling exhibitions. Chang and Eng both married and fathered a total of 21 children between them.
While separation surgeries of twins joined at the abdomen and other parts of their bodies, twins joined at the head are at a far greater risk.
The case of two US boys joined at the top of their skulls attracted global attention in 2016 as doctors successfully operated to separate them.