The neuro-ischemic diabetic foot

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The foot is a complex organ that performs its function by providing the information to the brain in the shape of sensations and by receiving motor orders from the brain.
A person has diabetic foot when the diabetic neuropathy and/or arteriopathy of the lower limbs compromise the foot function or structure.
These two situations, which are also defined as neuropathic foot or ischemic foot, are deeply different from each other: however, in most patients who are mainly of age, both neuropathy and vasculopathy coexist: this is when we talk about neuro-ischemic foot.

A serious complication of a diabetic foot that has an open ulcer is the infection, which is often the real cause that leads to amputation.
Peripheral artery occlusive disease (PAOD) is caused by plaques of lipids and other substances that narrow the vessel lumen. In diabetic patients, both legs are affected, mainly the arteries below the knees. Arteries are very often calcific; vessel total closure (occlusion) prevails over
partial closure (stenosis), stenoses are frequently multiple in the same artery (figure 9).

A typical characteristic in diabetic patients is the absence – due to the simultaneous presence of neuropathy – of the earliest symptom of peripheral artery disease: “claudication”.
Claudication is the pain that affects the calf after a given number of steps.
This pain results from the fact that the leg arteries receive less blood than the amount that is necessary for the effort to walk because they are obstructed.
The number of steps that can be taken before pain appears depends on the seriousness of the artery disease: they can be a lot or very few.
Also due to this reason – as well as other reasons – the diagnosis of peripheral artery disease in diabetic patients is not easy. There is a risk that its first sign may be an ulcer that does not heal or, in the most serious cases, gangrene. We resort to several diagnostic methods used simultaneously.

First of all, the presence of peripheral pulses must be assessed. The absence of posterior tibial or pedal pulse requires resorting to more sophisticated diagnostic methods. A simple method is the determination of pressure at the level of the malleolus: at present, there are very practical portable Doppler instruments that facilitate the use of this method. If the ratio between the pressure at the ankle and the pressure at the arm is below 0.9, there will most likely be a peripheral artery disease; the lower the ratio, the more serious the disease.
In this case, it is necessary to perform an eco-Doppler, which shows the location of the stenoses or occlusions. Perhaps the most important parameter is the transcutaneous oximetry, which measures the amount of oxygen that reaches the foot.

According to the results of these tests, the decision of whether to perform an arteriography or not is made. The arteriography is essential in order to decide whether the only therapy that is truly effective is feasible: revascularization, with angioplasty or with by-pass.

The critical point is the precise indication for revascularization: in fact, there may be an excessive indication but, above all, an underestimate of indication.
In practice, our indications are very precise: in case of claudication with a good free walking interval – for sure if it is above 200 metres – we prefer healing patients by giving them indications such as to increase physical exercise, to stop smoking, or to use antiplatelet and lipid-lowering drugs.

On the other hand, in presence of:
• pain while resting or claudication < 50 m
• ulcer or gangrene that require surgery

we give indications for revascularization, starting with angioplasty, which – when possible – is performed when the arteriography is performed.

Angioplasty is conceptually very similar to cardiac angioplasty: the exact position of the stenoses and occlusions is determined with the arteriography, and the obstructive plaques are dilated with a balloon. This procedure does not require general anaesthesia, it is not painful, it is very effective on the pain and on the possibility of healing the ulcer or of letting the ulcer heal, if necessary, by means of surgery. Complications are rare but still exist and must be explained to the patient. If the angioplasty is not possible, the possibility of a surgical bypass is assessed. It is very effective, but it requires a thorough assessment of the surgical risk. The important thing to be done when a foot ulcer is found is not underestimating the presence of artery disease: the risk is performing surgeries that – if a peripheral artery disease that has not been neither diagnosed nor revascularized is present – lead to further interventions until reaching the need to amputate the leg.

We would like to thank Dr. Giacomo Clerici (www.giacomoclerici.it) and Dr. Ezio Faglia for their kind contribution in clarifying concepts and providing explanations on this topic.

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