"It got worse … he was seeing doctors and specialists and they couldn't seem to get it right, it kept on spreading." Peter told the radio hosts.
"Basically he was told last week, you have a couple of months to live, or if you have your leg amputated, you'll probably have a few years. So, he agreed to have the leg amputated on Saturday."
He then went on to describe it as a "life or death decision that was presented" to the star, and one that would impact the rest of his life with wife, Patti.
"It's a big decision for anyone to make, but it's also a practical thing, because they live in a two-storey place with the bedrooms and the bathrooms upstairs, so they're now having to convert the house downstairs because Patti doesn't want him to go into a nursing home," he said.
Bert has dealt with a myriad of serious illnesses in the past, including several bouts of pneumonia and a stint in intensive care after undergoing quadruple heart bypass surgery.
His most recent hospital stint came in November last year with wife, Patti, sharing a snap of the TV veteran in a hospital ward.
"Bert's been in hospital, all good," she captioned it. "'He's Got a Lot of Living to Do."
After four-and-a-half decades, two children and six grandchildren together, Patti recently told Now To Love she would be lost without Bert.
"We lived and worked everything that was happening on television, we've spent a lot of time together. If anything happens to either of us, whichever one it is will find it very difficult because we've been in one another's pockets for well over 50 years," Patti says.
Bert has previously credited his doting wife for nursing him back to health during one of his many health battles, and we have no doubt she'll be doing the same now.
"Patti takes extra special care of what I do and particularly what I don't do," he said.
This story originally appeared on our sister site, Now To Love.