Post-op blood clot concerns

So, I’m talking about the same patient from that esophageal cancer post. He had surgery—they removed everything and basically rerouted his stomach up to his throat area, but that’s probably not really relevant to what's happening now—and he was discharged after two weeks. But then, just a few days later, he starts feeling this pain in his right leg, specifically on the outside of the knee. There's a slight swelling that just keeps getting worse over a 24-hour period. His fever shot up past 100.4. They've admitted him to the hospital (this time at Mayo Clinic) and they said they’ll be starting him on injections and some pills. Since I’m only here until Friday before I head out on my vacation—and I'm the one looking after him—I honestly have no clue what medications they're giving him, how long the hospitalization might last, or what the whole treatment plan looks like... Does anyone here have any experience or knowledge regarding this?
By the way, he actually had a deep vein thrombosis in that same leg once before and had surgery for it, maybe 8 or 9 years ago. He also has a long history of circulation issues.
On top of all that, a wound on his back isn't healing (he still has stitches), and now a sore on his heel has opened up too...
Hmm, I don't know... this feels bad, doesn't it?!

I guess I’ll start diving in... when I hear phrases like "why isn't the wound healing" or "the wound reopened," my mind immediately jumps to something like diabetes. Given how massive this surgery was, plus the fact that there was likely some malnutrition before the procedure and then basically "starvation" during recovery, my second thought is hypoproteinemia—it's pretty simple, really; the body just doesn't have enough raw materials to rebuild itself. And as a third possibility, we could be looking at microcirculation issues where the tiny blood vessels are so constricted that getting nutrients to the tissue becomes an uphill battle.
And honestly, it wouldn't be surprising if all those factors are hitting at once.

Regarding the immediate issue with the leg, a vascular surgeon absolutely HAS to evaluate this. That is non-negotiable!
Based on what you've described, it sounds to me like a moderate case of thrombophlebitis or phlebitis—basically inflammation of the vein lining, whether there's a clot involved or not. When you combine that with a recent major surgery, you have to be incredibly careful to avoid something as scary as a pulmonary embolism.
The treatment isn't anything too out there. You need plenty of rest, keeping the affected limb slightly elevated, applying local compresses made of half alcohol and half water, staying on top of pain relief, and most importantly, taking an oral or subcutaneous heparin product (like Lovenox or similar). As for antibiotics, follow whatever a doctor prescribes—never, ever experiment with elastic bandages or compression socks without a physician's okay.
In terms of testing, besides extensive blood work and coagulation panels, doctors usually run a color Doppler ultrasound on the limb to confirm exactly what's going on.

Thanks, thanks, thanks, Trevor. Honestly, I think you’re spot on regarding all three points. He’s been struggling with issues involving small blood vessel narrowing—Burger disease, or something like that, I can't quite remember the exact name—for years now. And because of the surgery, he isn't eating anything at all except for those protein shakes his doctor prescribed.
How long do you think they might keep him in the hospital? Do you have any idea what he might be facing once he's finally discharged?