The same excuse was used in August when a patient had a kidney taken out "inadvertently" during an operation to remove a pelvic tumour. The reason given was, again, that the patient had a "distorted anatomy".
Last December a woman had her ovaries removed by mistake, potentially triggering an early menopause.
Patients undergoing hysterectomies are often given the option of having their ovaries removed too, if they are at high risk of ovarian cancer.
In this instance the woman had not opted for removal but the surgeon took them out anyway.
In another alarming episode, surgeons got the wrong person altogether. On August 2 last year, a doctor at Great Western Hospital in Swindon, Wiltshire, performed an endoscopy - where a tiny camera on a probe is inserted into the body - on the wrong patient.
It occurred because the patient had the "wrong sticker" on them and there was a mix-up with consent forms, according to documents released under the Freedom of Information Act. The hospital offered "a sincere apology" but said there was "no long-term harm" done to the individual.
Common instances of "wrong site surgery" include wrong teeth being removed or the wrong eye being operated on.
"Wrong site surgery" is one type of "never event" - a mistake so serious it is never meant to happen in the NHS. Others include surgical items being left in the body, misplacement of feeding tubes and falls from poorly protected windows.
Health Secretary Jeremy Hunt is said to take "never events" so seriously, he keeps updated details of them on a whiteboard in his office.
Nonetheless, in 2015/16 there were 345 "never events" across the NHS in England, according to official figures, the highest figure in at least the last five years.
However, a spokesman for NHS Improvement, the new health watchdog, claimed the figures were not directly comparable because the definition of a "never event" had changed over time.
He added that the figures may also have risen because "the NHS has become better at being more open and transparent".
That explanation was also given by the Royal College of Surgeons (RCS), which said: "The drive towards greater reporting and transparency of patient safety incidents in the NHS in recent years may partly explain the rise."
Wrong site surgery could be "devastating for patients and their surgeon, even if no serious harm is done', said an RCS spokesman, who added: 'While these incidents are very rare, never should mean never.
"Learning from mistakes and using best practice and guidance to avoid such errors should be the priority of every medical and surgical team across the country."
