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," a source tells the publication. "The infection, that is being aggressively treated with strong intravenous antibiotics, is unfortunately not getting better. There are many concerns about his health."

Keeping Up With The Kardashians star Khloe is the only visitor allowed by his bedside until he improves, according to E! News.

Khloe has been by the athlete's side since he was hospitalised in Las Vegas on 13 October (15), after he was found unconscious at a brothel in nearby Crystal, Nevada. He woke up from a coma a few days later, and on Monday (19Oct15), he was airlifted to Cedars-Sinai, where he has been treated ever since.

On Wednesday (21Oct15), 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.