An 85-year-old woman who entered a Hong Kong hospital for a procedure to relieve a cancer-related bowel obstruction died weeks later after a surgeon mistakenly operated on the wrong organ, an error that investigators later described as the result of confirmation bias.

The woman, who was being treated for obstructive sigmoid colon cancer, was admitted to Tseung Kwan O Hospital in February for a transverse colostomy, a procedure to divert a section of the large intestine through an opening in the abdomen to bypass a blockage.

Instead, her surgeon inadvertently brought a part of her stomach to the abdominal surface and created a stoma, an opening on the outside of the body connecting to an internal organ.

The mistake went undetected for weeks.

A root-cause analysis released by the hospital noted that during the operation on 7 February, the surgeon wrongly identified structures inside the abdominal cavity, and proceeded without taking additional steps to verify the anatomy. The surgeon had fallen victim to confirmation bias, it said, becoming convinced he had identified the correct section of intestine and failing to seek further confirmation, The Standard reported.

The patient initially appeared stable after surgery. Her vital signs were normal, but clinicians observed unusually high output from the stoma – a warning sign that, investigators noted, should have prompted closer scrutiny.

Nine days after the procedure, on 16 February, she was transferred to Haven of Hope Hospital for rehabilitation.

There, the abnormal stoma output continued.

According to the analysis, healthcare workers failed to recognise the significance of the trend, while rehabilitation staff lacked sufficient experience caring for patients recovering from stoma surgery. Communication between the rehabilitation staff and surgeons at Tseung Kwan O Hospital too was inadequate, delaying reassessment and intervention, according to The Standard.

The woman’s condition deteriorated dramatically two weeks later.

On 1 March, she developed hypotension and tachycardia. She was transferred back to Tseung Kwan O Hospital where imaging scans finally revealed the devastating mistake: the stoma had been created in her stomach rather than her colon.

In spite of further treatment, she died from complications roughly three weeks after the operation.

The findings have sparked renewed criticism of patient safety standards within Hong Kong’s public healthcare system.

“The investigation findings were unbearable,” former lawmaker Michael Tien Puk-sun said after the report was released, according to the South China Morning Post.

“The authority says it will make improvements all the time following blunders. When will we really see improvement?”

Calling the error a “rookie mistake”, Mr Tien argued that it had damaged Hong Kong’s reputation as a centre for medical services and urged authorities to consider stronger disciplinary action against the surgeon involved.

Hospital officials accepted all of the investigation panel’s recommendations and said measures were already being implemented to strengthen patient safety.

Among the proposed reforms are a review of clinical governance within the surgery department, closer involvement of surgical teams after patients are moved to rehabilitation facilities, and a new system requiring specialist stoma and wound-care nurses to assess patients and rapidly report any concern back to surgeons.

The hospital has also begun restructuring its surgery department under a cluster-based management model intended to improve oversight and accountability.

While hospital authorities did not publicly disclose what disciplinary measures had been taken, local media cited sources familiar with the matter saying the professional performance of the surgeon, an associate consultant, was now under review. Options reportedly being considered include demotion, non-renewal of employment, or referral to the Medical Council of Hong Kong.