Need help with socially appropriate behavior:

Just received a message from a colleague that their wife (who's also my colleague) had an emergency surgery yesterday and now she's still in pain although now she's home. My colleague said "just wanted to let you know". Now I don't know how to respond to sudden events like this. Should I say something like "thanks for informing me...." Etc? I mean that's weird. I want to say something sensible that can convey my empathy towards the situation. Please help. I should also text the wife. But again I don't know what to say.