Red insisted on coming in too, and closely supervised the proceedings - any time I looked, there was Red's eye at one of the gaps between the stall boards.
After palpating it - which didn't bother him much - she said it felt like there was torn muscle. She wanted to do an ultrasound to confirm and also determine the character of the fluid to rule out an abscess. And in fact there was a significant muscle tear - mostly along the fascia line between one muscle segment and the next, although there was also some minor tearing of the muscle itself. That explains why it doesn't bother him much - the significant tear along the fascia doesn't hurt in the way that a tear of muscle fibers does. The fluid looked good - no sign of infection - mostly clear serum with a few fibrin blood clots. She recommended against draining it - it's clean in there right now and we don't want to risk introducing bacteria, and it is likely draining would provoke additional bleeding. So cold packs for a few days, then cold/hot, and Traumeel ointment. The swelling should subside over time, but he'll likely have a permanent bump. That's all good news to me.
And, since I was taking pictures of Pie's lump, here is some Red and Pie photo spam - the theme seems to be ears.
Fuzzy Red ears with a sprinkling of hay:
Skeptical Pie ears:
And Pie ears against the horizon: