When a pair of conjoined twin girls arrived at a New England hospital last year, doctors were presented with a gut-wrenching case.
In an extremely rare occurrence, the twins were connected by the abdomen and pelvis. They had three legs, one of which had a misshapen foot. Imaging tests showed they shared a single liver, while each child had one complete, which drained into a single bladder, and one undersized kidney. The gastrointestinal tracts were fused together. There was one anus and one vagina.
With the help of a non-profit organization the girls' parents brought them to the United States to seek treatment. They were 22 months old at the time.
One twin was larger than the other and was alert and interacting with caregivers, while the smaller twin was less active and less able to engage.
Requests were sent to around 20 hospitals across the country. Doctors at Mass General Hospital for Children agreed to take on the case, which they detail in a new report published in the New England Journal of Medicine.
The doctors were quickly hit with the realization that the smaller child, referred to as "Twin A," was dying – and not only that, she was slowly killing her sister, "Twin B."
"Twin B is normal and living relatively healthy and we know that she can live without her sister, whereas Twin A relies completely on her sister. Her sister is her life support," lead study author Dr. Allan Goldstein, M.D., surgeon-in-chief at Mass General Hospital for Children, told CBS News.
Testing showed Twin A's heart was undersized and had significant. She had underdeveloped blood vessels between her heart and lungs and relied on the blood supply from her sister.
Twin A became progressively sicker, with several episodes of respiratory distress that required admission to the pediatric intensive care unit.
It became clear to the doctors that Twin A would not survive surgery for separation. But her declining health made it likely she would die even if the twins remained conjoined. Her death would mean the inevitable death of her twin. There was also the chance that if separation surgery were performed, both twins would die.
The decision on whether or not to operate posed a complicated ethical question for the doctors. A pediatrics ethics committee was assembled to wrestle with the issues and weigh their options. Their discussions determined that, while each twin should be regarded as a distinct individual, there was little to no chance of saving the smaller twin; yet not attempting the separation surgery would risk her sister's life, as well.
Ultimately, after discussions with the team of doctors and support from a religious leader, the parents made the decision to proceed with the surgery.
"They were in a position where they felt that they couldn't continue with the same situation," Goldstein said. "They really wanted something done and knowing the high risk of the operation they said they would accept that risk."
"It was our job to say, is it feasible surgically and is it appropriate ethically?" he continued. "We're fortunate that ultimately we came to the decision that the parents' decision was not only by definition the right one because it was their decision but also it was appropriate from all other perspectives that we considered."
Still, the prospect was anything but easy for Goldstein and his team.
"We as doctors are trained to do everything we can to save every life we encounter," he said.
The 14-hour surgery went as expected. After the separation of the pelvic structures, the surgeons divided the arterial connection and Twin A's blood pressure and oxygen levels dropped, resulting in her death.
"I left the operating room and cried," Goldstein said. "I cry thinking about it now. It was not easy. But I don't regret it and I don't think anybody on the team regretted it because there's this beautiful 3-and-a-half-year-old girl and her parents are thrilled."
Arthur Caplan, Ph.D., the founding head of the Division of Medical Ethics at NYU School of Medicine, said that when it comes to the decision about whether to perform, "there's no one-size-fits-all answer."
"The issue is how are the twins conjoined," he told CBS News. "If they're really intermingled in a way where one twin has most of the vital organs and the other doesn't, and the parents want to separate, it becomes easy to know what to do."
And while medical principles say it is immoral to kill one person to save another, the cases ofcan be different.
"It's not a matter of killing A to save B," Caplan said. "What you're really asking is if A is going to kill B, is it OK to remove A? That's from different from making a choice between two equally valuable lives."
Goldstein said the surviving twin, who still comes in for regular visits and physical therapy to help her with walking, is now healthy and thriving. "She's eating and growing. She's happy. She's always smiling. She has a very funny sense of humor," he said.
The parents released a statement to the New England Journal of Medicine saying that their daughter is "doing very well."
"Everyone here was united for our family's cause," they said. "We couldn't be prouder or happier of how we all came together for the well-being of our child."