Lomu has dialysis three times a week

What does Lomu suffer from?
Lomu has Nephrotic syndrome, a kidney disease which causes a build-up of water in the body and allows protein to leak from the bloodstream into the urine.

How has this affected him?
After his diagnosis in 1996, Lomu had to take time out from rugby while he was put on medication in a bid to control the ailment. He did return to the sport but struggled to maintain his fitness because of the side-effects of the treatment.

And now he has been forced to sit out the New Zealand domestic season after managing just half of a warm-up match for his club Wellington.

Kidney failure and dialysis explained

The condition of his kidneys recently deteriorated to the extent that they now need dialysis to function. He is having dialysis three times a week for several hours at a time.

Can he play rugby during this period?
While Lomu's all-round general fitness should be an advantage, patients respond in different ways to dialysis.

"Some people lead very active lives while undergoing dialysis," says Tim Statham, chief executive of the National Kidney Federation. "I knew of someone who did a charity cycle ride from Land's End to John O'Groats."

But he adds: "It is a different way of life - you are tied to a machine for several hours a day for several days a week."

How long will he be on dialysis for?
Until he can get a kidney transplant.

Doctors in New Zealand are expecting a rush of people offering to donate one of their kidneys to Lomu but it is not that simple as donors must have blood and tissue types that are compatible with his.

A transplanted kidney usually lasts about nine years before it needs replacing.

If he has a successful transplant, will he be able to play international rugby once more?
Again, it depends on how Lomu's body reacts.

After a transplant, there is no reason why patients should not resume an active lifestyle, including playing sports.

However, rugby is a very physical contact sport and the risk of kidney damage means it is doubtful whether Lomu would ever grace the international stage again.

Have Your Say What now for Jonah Lomu?

New Zealand Rugby Union doctor John Mayhew says it is too soon to rule out a return to the sport.

"We'll get Jonah right, get him a kidney and then see what happens. It's feasible; I'm not saying it's probable," he said.

Because of compatibility issues, the average wait for a kidney in New Zealand is three years.

But Lomu himself remains hopeful that he will play top-class rugby again.

"The dialysis is making me feel much better, but unfortunately I can't play rugby yet. But I'm still determined to get back," he said.