The family also called the ED for help, having visited the department twice with the child, and was told to call Healthline.
The child was taken to the ED a third time, patient services director Dick Bunton said yesterday.
Improved supervision of junior medical staff in the ED had been introduced since the death.
A nurse assessment suggested discharging the child might not be safe, but no-one challenged the discharge.
The ''unexpected death'' last year was one of 33 mishaps causing serious harm or death in 2013-14.
The report includes a 34th event that ''nearly'' caused serious harm.
The Southern District Health Board report released yesterday was part of national reporting that revealed 454 serious adverse events in district health boards in 2013-14. Of the 454 reported cases, 73 patients had died, although not necessarily because of the adverse event.
Non-DHB providers, including private hospitals and aged-care homes, reported a further 104 adverse events.
An investigation into the child's death at Dunedin Hospital found the ED consultant was not sufficiently aware of the resident medical officer's inexperience in paediatrics. The consultant had failed to personally review the patient, the report said.
Mr Bunton said in an interview yesterday the cause of the child's illness could have escaped a senior doctor, too.
''This was a terrible thing to happen to a young child. Whether the clinical course would have been changed by doing something a day earlier, that's open to debate ...''
Asked about the nurse assessment, he said it had differed from that of the doctor.
''I think in general terms you might find that nursing staff are a little reticent to challenge what a doctor is saying, or what a doctor feels, and all we're saying is that everyone should be empowered to [disagree].''
The board planned to hold a workshop about how to challenge decisions in a clinical setting.
There should have been a low threshold for specialist referral for re-presenters to ED, the report said.
The policy of referring patients who call the department to Healthline continued - despite a recommendation to the contrary in an internal report - as to do otherwise would not comply with national guidelines.
A memo had been distributed in the department about paediatric patient discharge.
Other cases included an infant with a delayed diagnosis of subdural bleed. A report into that incident was still in draft form.
An unexpected abnormality noted on a chest X-ray was not followed up.
An alert on the X-ray from the radiology service for a potential chest mass was not noticed in the system by ED staff.
An investigation found that as checked results were not deleted, the report was ''buried'' from the checking physician.
Because the X-ray reporting was being done by an outside provider, calls from the external service were not as frequent as when performed by in-house radiologists.''
This is another important layer of back-up which has effectively been removed,'' the report said.
In one case, a patient was given strong pain medication intravenously instead of orally, and in another a patient was given medication meant for a different patient.
One person received surgery on the wrong eye. Mr Bunton explained that both eyes needed the surgery, but the eye in question had been set down for a different date.
There was no harm to the patient, but lessons were drawn from the mistake.
Also reported are the two big technology failures that hit the board - the loss of thousands of mammograms last year, revealed only in February, and an IT outage that disrupted hospital services in February.
The report lists 11 falls, accounting for nearly a third of the total events.
Nationally, falls accounted for 55% of adverse events.
Health Quality and Safety Commission chairman Prof Alan Merry said the increase in reported events this year was because of improved reporting.
Last year, there were 437 events, compared with 454 this year.
Of particular concern was the rate of falls.''
Ninety-eight people suffered a broken hip in hospital. This rate of harm is far too high, and equates to almost two patients every week suffering such an injury.''
It was disappointing given all the work that had gone into reducing falls, Prof Merry said.
New Zealand Nurses Organisation professional nursing adviser Kate Weston said the rise in adverse events since the reports started in 2007 could not be solely because of increased reporting and also reflected a lack of nurses.''
These accidents are the result of care rationing and sadly it happens every day.
The number of nursing hours is just insufficient to meet nursing needs of patients, both in hospitals and in the community.''
The decision as to what care to prioritise or leave out because of insufficient resourcing is an all too frequent moral dilemma for nurses,'' Ms Weston said.
