In a brief statement responding to news from the Otago District Health Board that the Southern Cancer Network audit of up to 32 referrals is unlikely to be public before Christmas, Mr Ryall said he had not thought it would take as long as it had.
He said he understood there were "some clinical issues".
The public was interested in the report and "so am I", he said.
Mr Ryall called for an urgent report on the issue in mid-October when issues raised by 26 Otago general practitioners became public after an informal survey conducted by South Link Health.
The board responded by organising the audit of the referrals causing concern to the GPs.
The GPs had expressed concern about access to the colonoscopy service, including some cases where they said patients who had all the accepted signs of bowel cancer had been denied the diagnostic test, only to later be found to have the disease.
Other concerns involved the change in access to routine surveillance colonoscopies for people considered to have increased risk of the disease.
Mr Millar said he shared the minister's frustration about how long the matter was taking, but the board also needed to ensure that clinicians had a fair chance to review the preliminary report and comment on it.
Board chief executive Brian Rousseau, in an email response to the Otago Daily Times, said the clinical service was developing its response to the preliminary report.
Then he expected the audit review team would consider the comments and amend or make final the report.
He would be "extremely surprised" if the report were made final before Christmas.
Asked if he could give any indication of the tone of the report, he said he did not believe it would be wise to comment on the preliminary report.
He added the board was looking at ways it could increase the number of colonoscopies and potentially other colonic evaluations, such as CT colonography and barium enemas.
Once the report was made final, it would be provided to South Link Health for distribution to the GPs who raised concerns, he said.
Not all patients from the GPs' survey or their families gave consent for the audit team to have access to their full clinical records, which meant they were not included.
The audit was to have been completed by the end of November, but this was extended until last Friday because auditing patient notes took longer than expected.
The executive director of South Link Health, Prof Murray Tilyard, did not respond to calls.
