A breast cancer patient from East Sussex died following a routine operation to remove a tumour from her adrenal gland after a surgeon mistakenly clipped the wrong blood vessels, cutting off the blood supply to her liver and gut, an inquest has heard.

Nicole Haynes, 35, had previously undergone an operation in 2011 to remove a cancerous tumour from one of her breasts when a further mass was spotted in one of her adrenal glands in early 2012, East Sussex Coroner Alan Craze was told.

The financial assistant, from Pevensey Bay, near Eastbourne, had keyhole surgery to remove the tumour on March 27 2012 because the doctors at Eastbourne District General Hospital were concerned the mass could be a secondary tumour related to Mrs Haynes' breast cancer.

During the operation, anaesthetist Naomi Forder noticed that Mrs Haynes' heart rate was slightly raised but put it down to adrenaline being released while the adrenal gland was handled as the tumour was removed, the inquest heard.

Her blood gases were also slightly abnormal but were not deemed to be unusual at the time, the hearing at Eastbourne Town Hall was told.

Steve Garnett, the urological surgeon who operated on Mrs Haynes, told the inquest he believed he had identified the blood vessels which needed to be clipped and that the operation had gone well.

But, he said, following Mrs Haynes' death it was discovered that he had "misidentified the vessels of the adrenal gland and clipped the wrong vessels", which were the main blood supply to the gut and liver, the inquest heard.

The hearing was told that, without the blood supply, the tissues had started to die and there would have only been a small window to correct the mistake before it was too late.

But because Mrs Haynes was under a general anaesthetic, the problem was not identified until much later on in the day when she was in pain and her condition deteriorated, the inquest heard.

Mr Garnett was called back to the hospital that night and said it was "clear that she was extremely unwell", Mr Craze was told.

Doctors ordered an immediate CT scan to find out what was going on but Mrs Haynes had to be transferred to the Conquest Hospital in St Leonards on Sea, because the scanner at the EDGH was broken, the hearing was told.

Once she returned to the EDGH she was transferred to King's College Hospital in London where she was operated on during the morning of March 28 2012, the inquest heard.

Mr Garnett said research he had undertaken following Mrs Haynes' death suggested that he could have become disorientated by the position of the cameras inside her body because the field of view was small.

He said: "In retrospect I was disorientated but I did not realise that at the time.

"If I had, I would have stopped the operation, reorientated the cameras and got a colleague to help.

"If I still wasn't sure, I would have opened up (to operate)."

Mr Garnett told the inquest that there had been no visual signs during the operation that the wrong blood vessels had been clipped.