SALT LAKE CITY, Utah (AP) -- Doctors began separation surgery Monday on 4-year-old conjoined twins in what was described as the first separation attempt on twins with a shared kidney.
Kendra and Maliyah Herrin are fused at the mid-torso and in addition to their kidney, share a liver, a pelvis, a pair of legs and part of the large intestine.
The girls headed to the operating room at 7:15 a.m. after a tearful goodbye with their parents.
The surgery at Primary Children's Hospital is expected to take between 12 and 24 hours, head pediatrician surgeon Dr. Rebecka Meyers said. Doctors at the hospital say it is the first known separation surgery attempted on twins with a shared kidney.
If all goes according to plan, each girl will get one leg and Kendra the kidney. Maliyah will be put on dialysis for three to six months until she's strong enough for transplant surgery, Meyers said. Their mother, Erin Herrin, is the planned kidney donor.
Surgeons also plan to bisect the girls' liver, separate their intestines and reconstruct their pelvis. Conjoined twins also commonly have several duplicate or undeveloped internal organs, which doctors will either fix or remove, Meyers said.
Conjoined twins occur about once in every 50,000 to 100,000 births. Only about 20 percent survive to become viable candidates for separation, and most separation surgeries occur when the twins are 6 to 12 months old.
But doctors advised waiting when they learned the girls shared a kidney. Subsequent plans for surgery were delayed because Maliyah had difficulty gaining weight and because Erin Herrin's pregnancy last year with a set of twin boys, who are not conjoined, made her ineligible to donate her kidney.
The girls, who have sandy-blond hair and blue eyes, have been preparing for surgery since June 23, when doctors implanted 17 expanding balloons into their torso. Filled with saline solution each week, the balloons have been expanding the skin and muscles that plastic surgeons will use in closing their abdomens after surgery.
Because of the significant risks of kidney dialysis and transplant for Maliyah, some ethicists who met with doctors and the girls' parents questioned separating the twins.
But Jake and Erin Herrin -- who also have 6-year-old daughter -- decided in February to proceed. They said the girls see themselves as living separate adult lives.
In a posting on the North Salt Lake family's Web site Sunday, the Herrins said they were "shedding many tears today. Not so much because we are scared or nervous, but because we are mourning their last day conjoined."
The posting also said the girls were excited about surgery and seemed to have no anxiety.
"We cannot believe how brave they are," the Herrins wrote.