CHRISTINA'S HELLISH NEW HEALTH BATTLE

Fears kidney anguish is tipping point in battle with MS

- 

COURAGEOUS Christina Applegate has been hit with a severe kidney infection on top of her ongoing ordeal with multiple sclerosis (MS) and people close to her say it's taking all the guts she can muster to keep on fighting.

"So much pain. I'm screaming, and they ordered me an emergency CT at 2 in the morning," said the former Married ... With Children actress, now 53, of a hospital scan showing that the infection spread to her left kidney, too.

"This has hit her like a ton of bricks and caused her unbearable pain, but she's a trouper and showing incredible resilience," says an insider.