ROT in hell!”

That was former child actor Macaulay Culkin’s shocking reaction to news that his father had suffered a massive stroke that left him at death’s door, say sources.

The troubled “Home Alone” star, 33, and his 69-year-old father, Kit Culkin, have been estranged for nearly 20 years, and while sources say Kit had hoped to mend fences, that’s not likely to happen.

“To Mac, there’s too much bad blood,” a close source reveal

Kit reportedly suffered a massive stroke on Jan. 21 at his home in Grants Pass, Ore., and was hospitalized in “very bad shape.” He’s lost almost all motor function and the prognosis is poor, according to a family source.

Two days after Kit was stricken, Mac could be found playing the kazoo with his band Pizza Underground at the MOSCOT Gallery in New York.

The actor hasn’t laid eyes on his dad since 1996, when Kit lost a highly publicized custody battle for his seven children and their $50 million fortune to their mother, Patricia Brentrup. Mac has claimed his alcoholic father physically abused him, and his semi-autobiographical 2007 novel, “Junior,” features an abusive father.

In a wide-ranging ENQUIRER interview in 1999, Kit said their rift began when he slapped then 15-year-old Mac during an argument over grades. At that time, we also reported that Kit, himself a former child star, had been diagnosed with ankylosing spondylitis, an incur­able spinal disease. Despite their estrangement, Kit broke down when we contacted him before publishing a bombshell report in August 2012 revealing that Macaulay was secretly addicted to heroin and struggling with a $6,000-a-month drug habit.

Although Macaulay’s reps denied the story at the time, Kit told The ENQUIRER: “I don’t want to see him die!

“Tell him he’s got to get off that stuff. Heroin will kill you. I made a lot of mistakes that I regret, but I still love him and it breaks my heart.”

Kit’s longtime live-in girlfriend, Jeanette “Cookie” Krylowski, told The ENQUIRER: “When Kit saw photos on TV of Mac looking skinny and sick, it ripped him up. He had to turn away. Despite all the years that have passed, Kit still has love for all his kids. But they completely abandoned him. When his daughter Dakota died, they didn’t even tell him. He had to hear about it from TV reports.”

Dakota passed away in 2008 after being struck by a car. Another daughter, Mac’s half sister Jennifer Adamson, died from a drug overdose in 2000.

Despite the animosity, the source said Kit longed to reconcile with his famous son.

“Once, when Mac appeared in a show in New York City, Kit traveled all the way from Oregon to watch from the back of the room,” said the source. “It’s unclear if Mac ever knew his dad was in the audience, but that’s the last time Kit saw him.”