Former manager Phil Kingsley Jones said "like everybody else in the world" he was wishing for Lomu to recover quickly.
"Jonah Lomu is a special person to us - not because he's famous but because of the person he is," Mr Kingsley Jones said.
"If you know him at all he's a great guy and we just wish him all the best. We hope he will come right - he's been through so much - and our thoughts are always with him."
All Black assistant coach Steve Hansen said the whole team were behind Lomu.
"[It's] really sad news. And obviously we don't know too much about it other than that he's in hospital. So the thoughts are with the big fella and hopefully he makes a speedy recovery."
Kidney Health New Zealand education manager Carmel Gregan-Ford said the condition Lomu had suffered from was one of many that could lead to kidney failure.
There were 2500 people in the country on dialysis and up to 400 on waiting lists for kidney transplants, Ms Gregan-Ford said.
"It's just luck of the draw - any member of the general public could be at risk."
Nephrotic syndrome was characterised by the loss of protein in urine, and in many cases a new kidney should make it go away, she said.
"People with transplants can last a year to 20 years [or more]. It just depends on the kidney.
"With transplants there's always a risk of rejection, or somebody can get a virus or infection like in any part of the body. You can certainly have more transplants if one stops working, but you deal with the risks every time.
"There are more people donating kidneys than there used to be, but supply doesn't equal demand."
Simple blood and urine tests could detect many kidney problems, she said.
