Khloe Kardashian's estranged husband underwent an unspecified procedure at Cedars-Sinai Medical Center, and the operation is said to be connected to a bout of pneumonia, according to People magazine.
"Lamar is in a very fragile state. The infection, that is being aggressively treated with strong intravenous antibiotics, is unfortunately not getting better. There are many concerns about his health," a source said.
"Keeping Up With The Kardashians" star Khloe is the only visitor allowed by his bedside until he improves.
He woke up from a coma a few days later, and on Monday, he was airlifted to Cedars-Sinai, where he has been treated ever since.
The pair reportedly signed a petition asking a judge to dismiss divorce papers that had yet to be finalised. The request was granted and reports suggest their divorce case is now over.