Hong Kong's hospital authorities have sought help from the mainland in a rare move to find an organ donor from across the border for a critically ill 37-year-old man suffering from severe liver failure.

The patient is in a critical condition in Queen Mary Hospital, according to the Hospital Authority, which said the man's kidneys are also severely impaired.

He was diagnosed with jaundice in 2019 before his condition worsened. The patient's mother, who's his only kin, was not suitable to donate.

Albert Chan, the director of the hospital's liver transplant centre, on Sunday said it is most ideal to find a suitable organ and conduct the transplant within a week.

"Once the 'golden hour' is passed, there's a possibility of infection or brain damage. Even if there's a liver transplant after that, the surgery will be more risky, and the patient may not fully recover even when it's successful," he said.

"Because the patient is relatively young, our medical staff hope there's a chance to help him... We've applied to the mainland [for a cross-border organ matching mechanism], and we're waiting to hear back."

Chan also said this was a one-off arrangement, hoping that the city could regularise organ donations with the mainland.

The Hong Kong Liver Transplant Patients' Association said some 80 patients are waiting for a new liver, but only 32 transplants were made last year.