Yuvraj`s mother, Shabnam Singh, made the revelation in a formal statement on Saturday.
"We didn`t have an intimation about this thing that came up. I was pretty surprised to know that this was the problem. I personally didn`t know this was the problem. I was very surprised and I wish him a speedy recovery. All of wish well for him and he is such a dear member to the team," Kohli said.
Yuvraj had declared himself unavailable for the one-day series against the West Indies because of the illness and was also not picked for the Test series in Australia. A golf-ball size lump has been found over Yuvraj`s left lung, according to his mother.
Kohli, who was picked at Yuvraj`s expense for the third Test against the West Indies, silenced his critics with fifties in both innings.
The Delhi player thanked Sachin Tendulkar who advised him to stick to his natural game. "I spoke to Sachin Tendulkar for about half an hour in the practice session before the game (Mumbai Test). I explained to him what mindset was in the West Indies, how I put myself under too much pressure, how I became too cautious. He helped me out immensely. He asked me not to change myself just because I am playing Test cricket," Kohli told `NDTV`.
Kohli was naturally satisfied with his performance in the third Test, especially after a none-too-impressive outing in the West Indies. "It`s pretty satisfying. To be honest, I didn`t have a great outing in the West Indies, and it was more of a disappointment for me as well as people who had expected a lot. I mean this was one format where I really wanted to make a dent. This is just the beginning. It really feels nice to have contributed in the one game I got in the series, and looking forward to Australia," he said.
Asked if would target any particular bowler in Australia, Kohli responded in negative. "We have seen all of them, played all of them. There is no particular bowler who can be targetted because they all are quality bowlers, quick bowlers. We need to give bowlers respect and put the loose deliveries away. That is Test cricket. We can`t take anyone lightly. I will take a lot of temperament and character to perform there."