| Education Material for Health Care Professionals: Newsletter Version
THE FEET AND DIABETES
The tragedy is that many of us do not pay adequate attention to the feet of our patients. How often do we instruct patients to examine feet daily and even take the trouble to show them how this should be done? For that matter, how often do we insist that the feet of the patient be examined every time they come to us?
Unfortunately even in specialised institutions which may pay attention to foot problems, the patient either gets some rapid oral instructions about foot care or may even be given a small slip of paper detailing briefly the instructions. Whilst, this may be better than doing nothing, it still does not solve the problem, because more often than not, the oral instructions are forgotten by the time the patients reache home and the small piece of paper is either filed or lost. Even if the patient were to remember the instructions to inspect the feet, does this really mean much to the patient? What is the patient supposed to look for? How are they supposed to look for any problem and how often? How can they care for the feet? What are they supposed to do in case of any problem, and possibly, more important, what are they NOT supposed to do!
So basically, whether your patient smiles or cries depends a lot on you!
Before we discuss the "do's and don'ts" about foot care, it would be worthwhile to consider briefly some of the mechanisms which predispose the patient to foot problems. This would allow us to instruct the patient in a much more rational manner rather than just giving him some "commandments" to observe.
Predisposing factors for limb-threatening lower extremity infections and ulcerations include neuropathy, macrovascular and microvascular impairments, as well as decreased resistance to infection, which is often referred to as immunopathy.
Nerve damage in diabetes affects the sensory, motor, and, the often forgotten, autonomic fibers.
Involvement of the sensory nerves going to the feet brings about many varied symptoms and signs but many patients have a marked reduction in the pain sensations and a significant number of the patients go on to have insensitive feet, and are incapable of feeling any type of sensation. The patient may not feel any pain or other uncomfortable sensations. Therefore, often they may not be aware of any the presence of any injury or infection until these may have progressed to a severe stage, or they are pointed out by a relative or the doctor. Thus it may not be possible to detect the presence of any injury or infection at a stage when management may be a lot easier.
Although diabetic neuropathy more commonly affects the sensory nerves, the motor nerves may also be involved. Motor neuropathy causes muscle weakness, atrophy, and paresis. The motor nerves which innervate the small muscles of the feet help in maintaining the shape and the "arches" of the foot. When these nerves are affected, there is a wasting of the small muscles of the feet and this may change the configuration of the foot. The toes may become “cocked” up and the area of the sole near the heads of the metatarsals comes to bear most of the weight of the body. This is made worse by changes taking place in the small joints of the foot due to diabetic nerve and bone damage. The change in the normal architecture of the foot accompanied by a decrease in the sensitivity is one of the most important predisposing factor in diabetic foot disease.
One aspect of neuropathy that is rarely given its due is the autonomic nerve involvement. They regulate the blood supply to the limbs, determine sweating and also maintain the normal texture of the skin. When these nerves are affected in diabetes, it may lead to a reduction or even a complete absence of sweating in the feet and the lower legs. A reduction in sweating causes the outer layers of the skin to become dry and this makes the skin of the feet, especially the skin on the soles of the feet, to become brittle, liable to develop cracks which may form entry points for infecting bacteria. The skin also loses its ability to stretch and therefore any change in the shape of the feet also tends to cause the development of breaks and cracks in the skin.
In some people, the clinical picture may be completely reversed. With the skin showing excessive sweating. This again leads to the skin becoming “soggy” and macerated, thus, making it more prone to injuries and allowing for easy entry of bacteria
The autonomic nerves are also responsible for regulating the blood supply to the feet and this supply is affected when the nerves are involved. Surprisingly, feet that are affected with autonomic neuropathy may appear warm and have been shown to have an increased blood supply. This increase in the warmth leads many to mistakenly feel that the circulation in the limb is adequate. This is definitely not the true situation. It is known that although the total blood going to the leg and feet may have increased, most of this blood is shunted directly from the small arteries to the veins, bypassing the capillaries. Therefore, although the total quantity of blood flow to the feet may appear to increase in diabetic neuropathy, this is of no real use and one could say that in practical terms there is a lack of blood supply to the feet.
Autonomic dysfunction (and denervation of dermal structures) also results in loss of skin integrity, which provides an ideal site for microbial invasion.
This can be further compromised by the presence of peripheral vascular disease, which is much more common amongst diabetics than in a non-diabetic.
We have already discussed how autonomic nerve involvement may lead to a real decrease in the supply of nutrients and defensive mechanisms in the foot although the peripheral arteries may be well palpable.
The earliest symptom of this could pain in the legs whilst walking, Some patients get pain at night when they are lying down but this can be relieved by hanging the foot over the edge of the bed and is increased if the patient gets up and walks around. The feet may feel cold, skin appears dry and parched, the nails lose their lustre and the small amount of hair on the toes may be lost.
We have seen that the feet of a diabetic with autonomic neuropathy appear warm whilst with peripheral vascular disease, the skin is cold. This may sound confusing but it should be realised that diabetics do not have a clear cut demarcation between those that have only a neuropathy and those that have only peripheral vascular problems. Most of them have varying degrees of both, and the clinical picture would depend upon the relative severity of the two conditions in any individual patient. In any case, neuropathy and vascular disease, in severe forms, presenting in the same patient is dangerous because the patient becomes prone to painless ulcers which are quite resistant to treatment.