A widespread computer fault meant that nearly 6000 hospital patients' electronic discharge documents, which can include instructions for the next steps in medical care, were not sent to their GPs.
The problem was identified after GPs noticed that anticipated discharge summaries were not arriving from hospitals, said the Canterbury District Health Board, attributing the failure to an intermittent fault in three of Health Connect South's five computer servers.
"Calls were received from a few GPs on Friday 26 June who hadn't received discharge summaries for their patients who had been discharged from hospital," the DHB said.
Between May 18 and June 26, discharge summaries failed to be sent for 4638 patients who had attended hospitals in Canterbury; 218 on the West Coast; and 1071 in South Canterbury.
The discharge document summarises a patient's symptoms, treatment and medications and provides instructions on any required follow-up.
In Canterbury, most patients are given a printed copy in addition to the electronic version that is sent to their general practice.
All of the un-sent electronic summaries have now been identified and sent to the patients' GPs.
The failure is being reviewed to learn how to prevent its re-occurrence.
"We are very sorry that this issue occurred and we apologise to everyone impacted," said Canterbury DHB chief medical officer Dr Nigel Millar, "particularly GPs, who are now receiving a large number of discharge summaries to review at once."
"If any patients are adversely affected by this delay I will be in touch with them individually."