An elderly woman was left unaware she had a tumour in her colon for four months after doctors forgot about her test results, the Health and Disability Commission says.

The 81-year-old woman, who had a history of bowel cancer, was referred for a colonoscopy at a public hospital after complaining of tiredness.

The GP who referred her did not set a reminder on his computer for the test results, as he did not know how to use the task manager system.

A few days later the woman's family asked a different GP to instead organise a CT colonography privately.

The woman's GP did not communicate the change in care to the previous doctor, and also failed to set a reminder on his computer for the results of the CT colonography.

The CT colonography identified a tumour in the woman's colon.

She was not told about it until nearly four months later, when a third doctor finally traced the results.

Surgery to remove the tumour was performed soon after the results were received.

Despite contact from the woman and her family asking for the result, staff at the medical centre had not followed up on it, Deputy Health and Disability commissioner Theo Baker said.

Instead, the woman had been told that "everything was fine".

Neither of the first two GPs had followed up on their referrals, and the results of the radiology service had been lost after initially being sent to the wrong medical centre.

The commissioner found the GPs and the medical centre breached the Code of Health and Disability Services Consumers' Rights because they did not take reasonable steps to follow up their referrals.