Pest controllers were called into a Notts hospital after a rat was found in an operating theatre.
Around 40 operations were cancelled at King's Mill Hospital when the rodent made its way into the room last Tuesday night.
Hospital bosses have assured patients there is no need for concern.
Karen Tomlinson, Director of Operations said: "We are proud of our services and the extremely high quality of care we offer to our patients, so we were extremely shocked to learn that there was evidence of a rodent having entered a decommissioned operating theatre during the night, at a time when the department was not in use.
"As soon as we became aware of this fact the following morning, we immediately took steps to thoroughly clean and sterilise the entire theatre area and called in external pest control experts to completely eradicate the problem.
"Whilst this work was underway, all surgical procedures were halted for one day and just over 40 patients had their operations rearranged. We have apologised to any patients affected for the inconvenience caused.
"I would like to reassure any concerned patient or relative that this was a minor, one-off incident that occurred over a week ago. We took immediate and comprehensive action to rectify matters and to restore services with the minimum of disruption. We are fully operational again. There is no cause for concern."
The incident is the latest in a series of bad news for the debt-ridden hospital, part of the Sherwood Forest Hospitals NHS Foundation Trust.Tracey Doucet, chair of the trust, stood down at the beginning of October. Health watchdog Monitor said in September that it would act over the hospital's increasing debt, and said it was concerned "extremely concerned by the very serious issues facing the trust".At the beginning of October, it also emerged that around 80 breast cancer patients had been given inaccurate results.
