Conjoined twins from Bhutan were separated at an Australian hospital Friday in a delicate operation that divided their shared liver and reconstructed their abdomens.

The 15-month-old girls, Nima and Dawa, were doing well after the surgery that lasted almost six hours, said Joe Crameri, the head of pediatric surgery at Melbourne’s Royal Children’s Hospital.

“There weren’t any things inside the girls’ tummies that we weren’t really prepared for,” he told reporters.

The girls were joined from the lower chest to just above the pelvis. They shared a liver, but doctors started the procedure unsure if they also shared a bowel. Crameri said there were no major problems with the bowel attachment.

He said the major challenge had been to reconstruct the twins’ abdomens.

Crameri said the girls would be closely monitored and that his team felt “quietly confident that we will have a good result.”

He added that the girls’ mother, Bhumchu Zangmo, was “smiling, very happy, and grateful.”