A pair of twins sharing common organs is much more difficult to deal with. In some cases there is no possibility of being able to separate them, while in others separation will certainly mean the death of one child. Sometimes twins only have a shared liver. This is helpful to surgeons because, unlike other organs, the liver can grow back to normal size after a large part of it has been cut away. In such a case the liver is drained of blood before being divided, using an ultrasound probe to detect blood vessels, which are sealed with a medical glue.
Infection is a constant worry for surgeons.
In 1995 Chloe and Nicole Astbury, who were joined at the breastbone and shared a liver and bowel, died from infection despite the best attempts by doctors to save them. London's Great Ormond Street children's hospital is one of the few centres that has had any success separating Siamese twins. Professor Lewis Spitz, professor of paediatric surgery, has operated on six sets of twins at the hospital. At least seven of the 12 children have survived.