A five-year-old boy allegedly raped on Nauru is one of 90 children who face being returned to the offshore detention centre, where his rapist is still detained, ABC's 7.30 reports.

Paediatrician Karen Zwi has risked prison time to reveal the traumatic case of the young boy ahead of a High Court decision that will likely decide whether the children are sent back to Nauru.

Pediatrician Dr Karen Zwi appeared in the ABC report.

Dr Zwi said the boy suffered from intense mental trauma as a result of the alleged rape.

"Like many other children who are very distressed he regressed, he began bed-wetting, he became very anxious about his mother's well being, he actually began to self-harm, as I've seen several other children do as well, and eventually he was transferred over to the mainland for treatment," Dr Zwi told 7.30 in a report aired Tuesday night.