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Blood Flow in Diabetic Feet

Dry gangrene of the toes

Grass grows where there is water. Without water, it will dry up. The same thing happens to our body if deprived of blood, and our toes start developing dry gangrene. However, there are lots of things that has to happen before gangrene develops. There are also warning signs to look for that we will discuss. Let’s start from the beginning.

1) It begins with small blockages of the arteries


Diabetes causes problems with blood flow by creating blockages in the arteries, called atherosclerosis. At first, blockages are small. We can’t see or feel them. If they get big enough, they make the inside of the arteries smaller, which means less blood flow.

2) Next, we get leg cramps

When we are sitting down, we don’t need much blood to our leg muscles. When we walk however, our leg muscles are working much harder than when sitting, and so there is a bigger need for blood. A small blockage in an artery may allow enough blood to the leg muscles when sitting, but may not deliver enough blood when walking. The result is experiencing a leg cramp. This part is important. Leg cramping is the ONLY symptom that can warn you of problems with blood circulation. At first, the cramps will only be there with walking or exercise. During exercise, the muscles of our legs and feet use up more oxygen than can be delivered. If we stop to take a break, the cramps go away. After walking again for a bit, the legs cramp come back. This pattern is called intermittent claudication. If you have this, do NOT stop walking or exercising.

If the blockage worsens, we will start getting leg cramps even when we’re sleeping. This is called rest pain. The cramps will go away when we dangle the leg off the edge of the bed. This is because dangling uses gravity to help bring blood back into our legs. If you have this, I recommend you see a foot doctor or vascular surgeon. A test tells us if your pain is related to blood flow is called an ankle-brachial index (ABI). It is basically a blood pressure test of your legs compared to the blood pressure of your arm, and will tell the doc if you have a blood flow problem.

3) Blockages can worsen

If you become less active because of the leg pain and cramping, then blood supply to the feet will start to decrease. Our body follows this rule: If you don’t use it, you lose it.

Here are a few things that can be done for people with intermittent claudication or rest pain.

Stent angioplasty

Vein bypass surgery









4) Development of gangrene

Exercise and surgery can help bring blood to the foot. However, if it gets to the point where the arteries are completely blocked, there will be no blood flow. When there is no blood flow, flesh will start to die. The skin will look black, dry, and shrunken. This is called dry gangrene. However, dead flesh can easily get infected if not taken care of. Once it gets infected, there will be a lot of drainage oozing from the border between living and dead flesh. This is called wet gangrene and is a surgical emergency because the infection can spread rapidly.

Bringing It All Together

Leg cramping is the first and only sign of a problem with blood flow. Gangrene takes place long afterterwards, when the blockages get so bad that there is no blood flow.

This animation puts all of this information together. We start with a small blockage which we won’t notice. If it grows big enough, we will start getting leg cramps. If we stop exercising, the blood vessels will start to shut down. If enough blood vessels shut down, gangrene begins to develop. There is a lot going on inside the blood vessels that we can’t see or feel. The first and ONLY thing we would notice is leg cramping. From there, a lot still has to happen before we reach the point of developing gangrene. There are also things we can do to avoid reaching that point, such as exercise and seeing a vascular surgeon.

In summary, if you have no leg pain, keep exercising. If you intermittent claudication, keep exercising and consider seeing a foot specialist or vascular surgeon. If you have rest pain, definitely keep exercising, also definitely see a foot specialist and vascular surgeon.

Medical Information Disclaimer:

I am a podiatrist, not a vascular surgeon. You should follow the advice of your vascular surgeon if you have these problems.

Dr Haywan Chiu, DPM Haywan Chiu

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