An Indigenous man who died in the aftermath of a misdiagnosis at a regional NSW hospital could have survived if his stomach ulcers were detected, an inquest has been told.

The hearing into the death of Kamilaroi-Dunghutti man Ricky 'Dougie' Hampson Jr, 36, is analysing the circumstances that led up to his death after presenting to the Dubbo hospital emergency department on August 14, 2021, with "ten out of ten" pain and feeling a "popping" sensation in his stomach.

He died from two perforated duodenal ulcers, less than 24 hours after being discharged, having been misdiagnosed with a drug-induced syndrome, despite showing limited symptoms of the condition.

The inquest previously heard emergency doctor Sokol Nushaj admit his diagnosis of cannabinoid hyperemesis syndrome (CHS) for Mr Hampson Jr was wrong. During his evidence, he said "cognitive bias" influenced the error, having had treated other patients with CHS, as well as recognising Mr Hampson Jr's symptoms of agitation and pain.

However, the key symptoms of vomiting and nausea associated with CHS were never displayed by Mr Hampson Jr.

"It was the wrong diagnosis," Dr Nushaj told the coroner last week. "It is a matter of deep regret."

Mr Hampson Jr was given droperidol - an intravenous drug used to reduce vomiting and nausea - along with morphine. Its administration was never recorded by any doctor at the hospital.

In his closing submission, counsel assisting the coroner, Simeon Beckett SC, told the inquest the treatment of Mr Hampson Jr at Dubbo hospital was "inadequate and below the peer-professional standard".

"The diagnosis Mr Hampson Jr had CHS was influenced by the fact that he had used cannabis and Dr Nushaj had seen many Aboriginal people with that syndrome," he said.

"The following conduct of Doctor Nushaj on 14th and 15th of August 2021, constituted, in my submission, that the knowledge, skill, or judgement possessed, or care exercised by him in the practise of his profession, may be significantly below the standard reasonably expected of a practitioner of an equivalent level of training or experience."

Mr Beckett further noted: "It is very likely Dougie's death from the two duodenal ulcers could have been avoided if emergency staff on duty on August 14 had properly investigated his illness and referred him to a surgeon".

His submission mirrored the evidence of Associate Professor Anna Holdgate, who told the inquest on Monday a CT scan should have been ordered for Mr Hampson Jr, followed by "immediately notifying the surgical team, who would recognise it as a surgical emergency".

"If it is recognised early and treated early you would expect him [Mr Hampson Jr] to survive…and live a normal life," Dr Holdgate said.

Deputy State Coroner Erin Kennedy is being asked to consider whether factors such as bias and racism played a role in the medical treatment Mr Hampson Jr received.

Mr Beckett said it would be open for the coroner to find if bias played a role in Mr Hampson Jr's death.

Callan O'Neill, who is acting on behalf of Mr Hampson Jr's parents, Rick Hampson Snr and Lydia Chatfield, agreed with Mr Beckett's submission to the coroner, but expanded on the issue of racism in health settings.

He said the Royal Commission into Aboriginal Deaths in Custody (RCIADIC) was handed down in 1991, when Mr Hampson Jr was seven. He told the inquest if many of the recommendations had been implemented, perhaps Mr Hampson Jr would still be alive.

"Instead, he lived in fear of hospitals, and justifiably so," Mr O'Neill said.

After a series of recommendations to the coroner, including for more culturally safe practices at hospitals for Indigenous people, for Aboriginal liaison officers be stationed at Dubbo hospital 24 hours a day, and a plaque be erected at the hospital to memorialise Mr Hampson Jr, Mr O'Neill repeated the sentiments of Rick Hampson Snr.

"Indigenous people in this country have been hearing sorry for generations," he said.

"This is not a new matter.

"Sorry does not change medical outcomes. Sorry does not bring back loved ones who have died in our institutions and systems.

"Only change can make a difference and only change would be justice for Dougie."

The inquest is due to close on Friday.

13YARN 13 92 76

Aboriginal Counselling Services 0410 539 905