I've been meaning to post this here. This is well over a year ago. This is my own IV complication story; a pretty bad abscess at my mainline. Keep in mind I always did it "by the book," fresh works, alcohol swabs, etc. So this can happen to anyone. (This is shooting NYC powder dope from a dealer I'd been using for a long time and was always consistent.) But with this, I felt something wrong within a few minutes(this is not always the case btw) and within 24 hours there was a tennis ball size swollen abscess right there.
Before, and this is not a very good picture, my mind was not on taking a good picture, believe it or not

while this was going on … this is roughly tennis ball sized, ~1.5-2cm elevation, and produced 250-300mL of purulent discharge within the first 12 or so hours, lesser but consistent afew mounts over the next 24-36 hours, and eventually just a manageable amount on each dressing change which could be done about every eight hours, when initially needed to be done every two or so; at worst it was associated with a 101~102.5° degree fever, which broke within ~24 hours of drainage. This is not necessarily a typical course; medical care is required, probably not hospitalization, but definitely a visit to the ER unless you know what you're doing. I wound up doing the incision & drainage myself, at home, but I am professionally trained to do this sort of thing, and keep a lot of medical/surgical kit at home. Even then, I *should* have gone to the ER. If this happens to you, you *should*must* go to the ER even if you're a doctor yourself. A lot of people in the medical professions like to just treat themselves (a lot are very serious about their revular checkups by their own provider, too, this is much wiser but I fall into the former group) it's not generally a good thing especially if you're an addict on the side. This is bad news stuff.
Here it is after incision, drainage, irrigation with sterile saline, etc. and dressing changes, and eventually healing (some months after the above) there is about a 20mm deep crater of induration which is composed of mostly smooth skin over hardened, fibrous tissue. I expect it to stay more or less like this for a long time, and never go away. With a suitable sized needle, the vein is, in fact, accessible, with a not inconsiderable amount of difficulty as this is hardened, fibrous tissue, but to use it again with any frequency would be unwise to say the least.
As a result, the prospect of me wearing short sleeve shirts in a work environment questionable at any time in the remotely near future.
This is it today, almost 18 months later: