Why do physicians amputate your limbs if you have gangrene?

We try not to!!: Gangrene is often associated with severe pad (peripheral arterial disease). Frequently, providing better blood flow can help avoid major amputation. Sometimes this can be achieved with a minimally invasive procedure called angioplasty; other times, a bypass surgery is done to bring blood flow around the blocked segments of artery. Any patient with gangrene should be evaluated by a vascular surgeon.

Risk of Infection: Leaving a gangrenous portion of limb poses a high risk for infection and sepsis.

Gangrene: Gangrene represents a loss of circulation. With a loss of circulation the tissues lose the ability to fight off infection. At that point if infection sets into the tissues it can lead to sepsis. This can lead to death. So when gangrene is identified to be wet or infected it needs to be removed. Dry gangrene can be closely observed by well trained professionals.