A surgeon potentially saved the life of an old schoolfriend by diagnosing his symptoms for appendicitis on Facebook.
Rahul Velineni, from the Princess of Wales Hospital, Bridgend, saw Peter Ball's status update on his stomach pains and his trouble walking.
He sent the 30-year-old from Cheshire a message telling him he should see a doctor immediately.
By the time surgeons operated, Mr Ball's appendix was already perforated, which could have been fatal.
He has thanked his old schoolfriend for offering crucial advice at exactly the right time.
Mr Ball had been suffering from stomach ache for a while and at first thought he had pulled a muscle.
As his symptoms became worse, he decided to put himself to bed, posting an update that he was "walking like an old man" on his Facebook page.
He said: "I woke at about half-three in the morning in pain and saw I had a message from Rahul asking me to call him and saying he thought I might have appendicitis.
"The message really hammered home how important it was that I get this checked out."
Deciding not to disturb Mr Velineni in the early hours, Mr Ball instead took himself to his GP first thing and was referred to Macclesfield General Hospital.
He said: "By 7.30 that night I was in the operating theatre having my appendix out.
"The doctors said it had already ruptured. It was surprisingly serious.
"When I got home I phoned Rahul and thanked him profusely - I definitely owe him a few drinks for this."
Mr Velineni said that appendicitis was often difficult to diagnose, but he had thought his friend's status update sounded "odd".
"At once a light bulb went off in my head and I took the decision to get in touch with him.
"Thankfully he went to see his GP and the cycle started, because he had a nasty appendix and it was taken out."
The surgeon remained modest, however: "I think the people in the operation saved his life - I just gave him a kick in the right direction."
Mr Ball said he generally only used Facebook for staying in touch with friends.
"Something like this shows it can be about saving lives too," he said.