In a story that attracted worldwide attention, the Herald on Sunday in September reported that when the man sought help at the hospital, he was sent for x-rays and a scan.
These showed an eel which a hospital source told the paper was "about the size of a decent sprig of asparagus".
It was unclear how the eel came to be inside the man's rectum. It was believed hospital staff removed it and the man was later discharged.
It is understood staff are alleged to have emailed the x-rays. Media organisations are said to have a copy of one, but have chosen not to publish it. Neither the Herald nor the Herald on Sunday has the image.
"[The management] have investigated anyone who had access to that patient's file and are interviewing the staff concerned as to why they accessed the file," the source said yesterday.
"They are interviewing those who accessed the file who had nothing to do with the patient. There's a feeling in the hospital this is being taken a little far and becoming a bit of a witch-hunt."
Senior doctors' union executive director Ian Powell said: "There has been an over-reaction in that there is no support for anybody who may have leaked it to the media, but for people who have accessed it in a way that they would normally access an interesting and different case for learning purposes, that's going over the top."