Helen Reynolds, 51, from Rugeley, Staffordshire, originally visited Spire Birmingham Hospital in 2013 to have a gastric band fitted as part of her efforts to become a fitter person.
But after her initial operation was unsuccessful, she then went to Spire Manchester Hospital.
Desperate to begin her healthy lifestyle, Ms Reynolds had a gastric bypass operation at the end of January 2014.
But just months after the op, she found herself in crippling pain. Doubled over at home, she was startled to find blood in her urine and contacted doctors immediately.
But she was left frustrated after doctors dismissed her concerns as hormonal changes and sent her home. She said: "I suffered for months and months with excruciating pain in my stomach, which I can only describe as like contractions during labour.
"I was doubled up at home with my head in my hands on the floor in pain, it was that bad.
"There was blood in my urine and I was in excruciating pain, but the doctor told me that it was the menopause and trapped wind.
Over the next year, she endured seemingly endless waiting while doctors puzzled over what could be wrong with her. When, eventually, she underwent a sonogram, Ms Reynolds was told that she had what appeared to be cysts on her ovaries and had an operation arranged to inspect them. But she says that after Spire Little Aston Hospital took the trouble to anaesthetise her, they immediately stitched back up again having spotted that the cysts were in fact two-and-half inches of plastic tubing, left inside her from a previous operation.
Ms Reynolds added: "I had a CT scan which revealed that there was a foreign body near my right pelvis bone – I was completely shocked. I was so angry when I found out what it was.
"I was annoyed that I was never believed and told that I was just experiencing the same hormonal changes that most ladies my age developed. You eventually persuade yourself that the doctors are right that it is you who is wrong. But the doctor in Manchester admitted to me that it was his tubing that had been left inside of me.
"When they realised their mistake, they got me into surgery as soon as possible."
After the plastic tubing was discovered, she had to wait another two weeks before she could have the piece of tubing that had caused her so much pain removed. Her ordeal was finally over at the end of May 2015, a year-and-a-half after it began.
A spokesperson for Spire Healthcare said: "At Spire Healthcare, our top priority is always the welfare and safety of our patients. We take this responsibility very seriously and set extremely high standards across our hospitals."