Jonah Lomu's crippling kidney disease means he won't fight in boxing's Fight for Life next month.
The 36-year-old is on dialysis and the future of his transplanted kidney appears bleak.
At last night's IRB rugby awards ceremony in Auckland, Lomu said that he had withdrawn from the event.
Doctors at Auckland City Hospital have told the former All Black star there is only a slim chance his kidney will survive.
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It is not yet clear whether he will have to return to the transplant list, but tests are being done to see if the failing kidney can be revived.
Lomu played a key role in the Rugby World Cup opening ceremony on September 9 and appeared healthy and active.
But days later, he struggled to hold down his food, a problem that persisted for 10 days.
The rampaging All Black winger was rushed by ambulance to hospital on September 23 after struggling from nausea and weight loss, and is now on daily dialysis in hospital.
A kidney donated to him in 2004 was believed to be shutting down, which meant his body was struggling to clear waste from his system.