An individual with diabetes and an untreated an infection inside a foot or leg may build gangrene. Gangrene includes tissues dying due to extreme infection or reduced blood source. What to do about this: Should you have (or suspect you've) any of such ailments and spot new or persistent swelling https://www.sgvascularctr.com/swollen-leg-why-do-i-have-it-and-what-can-i-do/