A jury at Southport Coroner's Court returned a rare verdict of misadventure contributed to by neglect on Thursday.
Nineteen-year-old Karen Murray from Southport, Merseyside, collapsed while in holiday in Corfu in 1998.
During the post-mortem five plastic surgical clips and strips of surgical gauze were found in her abdomen.
A jury at Southport Coroner's Court returned a rare verdict of misadventure contributed to by neglect on Thursday.
It said she had been killed because five nine-inch square medical swabs had been gradually strangulating her bowel since an operation at Liverpool's Alder Hey Children's Hospital years earlier.
Karen had two operations for a rare bowel problem in September and December 1990.
The inquest heard that all the swabs used had been accounted for but a document to say they had been counted back in after the operation had not been signed.
She had an x-ray at Southport and Formby Hospital in 1996, after being admitted with severe abdominal pains, which indicated that there were foreign objects in her stomach.
Fear of doctors
But the surgeon who examined her believed she had eaten something which would pass through her body and did not consider her to be in any danger, the inquest heard.
Karen, who was said to have a fear of doctors, failed to turn up for three hospital appointments to investigate the problem further.
Paul Walker, Miss Murray's brother, said after the verdict: "It has been a long two-and-a-half year emotional and traumatic period for the family.
"We would like to thank everyone for their support and I speak myself for the rest of the family.
"We are happy with the verdict that has been given. When more time has passed we will evaluate the verdict."