SDHB chief medical officer Dr Nigel Millar said the external report, released today, reviewed 20 cases from recent years, which were selected because of concerns about their management.
The report - the Assessment of Diagnostic and Treatment Times for Endoscopic Cases - identified delays in diagnoses in 10 of those cases, during a period when "many thousands'' of colonoscopies were performed.
The 50-page report raised "important issues that need to be better understood'', but changes were already happening, Dr Millar said.
The SDHB had already moved to align its processes for accessing colonoscopies at Dunedin and Southland Hospitals, he said.
It would also be undertaking a further review and investing in "building stronger internal relationships'' to improve the handling of cases in which endoscopies were requested, but standard criteria were not met.
The further review would look at 102 cases where questions have been raised around patients' care pathways.
Dr Millar said any case of delayed care needed to be taken "seriously'', but bowel symptoms - such as pain and bloating - were for many people not the result of gastrointestinal tumours.
It was "impractical'' to investigate everyone with symptoms, so additional risk factors were applied to narrow the field.
"Unfortunately, there is always a possibility this misses some cases in people who are referred, but not accepted, for publicly funded colonoscopy.
"However, widening access to colonoscopy, to investigate symptoms that have been shown to be less likely to be due to gastrointestinal tumours, has the unintended consequence of developing longer waiting lists, and delaying access to those patients with symptoms shown to be more likely to be associated with a cancer diagnosis.
"This is a challenging balance to strike, and we appreciate the sincere concern all clinicians experience, and have shared with us, in managing this.''
The challenge was why it was "so important'' the SDHB had joined the national bowel screening programme, and had participation rates among the highest in the country, particularly for Maori.
The programme had so far detected 80 cancers that would not otherwise have been detected, and polyps - or pre-cancerous lesions - in over 700 patients.
