I am (or possibly was :() planning on running the Austin Marathon this coming Sunday. Logged plenty of miles during the last couple of months, all in same shoe (replaced when worn), on pavement, running from mid/forefoot. Started to taper down running volume after last 20 miler weekend before last. Went for last long-ish run (12 miles) yesterday in 40-some degree weather. Was warmed up and just cruising along, when suddenly after ~5.5 miles a sharp pain developed in my left lower leg, slightly above and to the left of the Achilles, over ~100 yards. Slowed to a walk, it went away, started running again, it came back. Shifted to the heel, it went away but came back for good after another ~300 yards. So I decided to call it, and walked back home; walking is no problem, I can also point the toe without any pain
Now, I was well rested, warmed up properly at that point, and don't have a history of injuries. Some online research leaves me a bit confused if the painful part is still considered the Achilles, or if it's the soleus. What I'm wondering is if anybody had a similar issue in the past, and what the solution was (I'm icing it and am not running for the time being). I have an appointment with a specialist on Wednesday, but am wondering if there's anything else I could/should be doing, and if the Marathon is a write-off.
Good thing is that I got my base miles from all the running :), and the marathon is just a 'target of convenience', if I have to drop out it's not too big a deal/disappointment.

Thanks for any thoughts!

- Stephan