An anaesthetist who faced being charged with sexual assault after rectally examining an unconscious patient at the behest of the operating surgeon says he was motivated by “clinical curiosity”.

The doctor had been involved in an operation on a 37-year-old man who had been admitted for a colonoscopy and biopsy of a posterior rectal mass at a Sydney hospital last year.

A tribunal was told the colorectal surgeon had invited him to examine the man because it was “a once-in-a-lifetime opportunity to feel” a large gastrointestinal stromal tumour.

It was claimed that the surgeon took photographs using his mobile phone of him performing the examination and promised to send them to other anaesthetists.