In reply to Chris_Mellor: If your leg is swollen to the extent you've described then it sounds like it's a femoral clot.
If you've already seen a doctor and they've suggested surgery then that's the obvious choice. As mentioned previously, normally clots are managed by anticoagulation drugs at a treatment dose, then a maintenance dose plus regular blood tests as a carry-on. Once you get on the regular prevention treatment then it probably won't affect your climbing much, as being able to mobilize is the key to preventing clots. Just be careful when you have to hang in a harness (work a route) for a long time as that'd obviously have a slight impact on blood flow.
Occasionally surgery is required, as perhaps with your case, and although it may seem like it'll cause problems to your climbing in the mean time, it's worth sorting the clot out sooner than later. The risk of clots is that it can dislodge and get moved around in your body, and when it reaches somewhere like a big artery in/near your heart or even up in your brain and then decides to get stuck again that could result in a heart attack or stroke, which the outcomes are obviously, we all know, not nice, and certainly will have a much bigger impact on your climbing.
Anyway, listen to what the medics say and try not to carry out too much "medical research" online
Get well soon!