A man is said to have arrived at Auckland City Hospital's A&E last week, reports the New Zealand Herald.
The unidentified patient was sent for X-rays, which revealed that an eel was stuck inside him.
"The eel was about the size of a decent sprig of asparagus and the incident is the talk of the place," a source stated.
"Doctors and nurses have come across people with strange objects that have got stuck where they shouldn't be before, but an eel has to be a first."
The man was later released from the hospital after the eel was successfully removed from his anus.
The Auckland District Health Board confirmed the incident earlier this week.
"We can confirm that an adult male presented at Auckland City Hospital this week with an eel inside him," a spokesman said.
He added: "No further comment will be made out of respect for the patient's right to privacy."
It is currently unconfirmed how exactly the eel became stuck inside the patient.
A man in China had an eel removed from his bladder after it entered his body through his penis last year.