Diabetes & The Body

Diabetic Foot Ulcers

What causes diabetic foot ulcers?

Diabetic foot ulcers are caused by neuropathic (nerve) and vascular (blood vessel) complications of the disease.

Nerve damage due to diabetes causes altered or complete loss of feeling in the foot and/or leg. This is known as peripheral neuropathy. Pressure from shoes, cuts, bruises, or any injury to the foot may go unnoticed. The loss of protective sensation stops the patient from being warned that the skin is being injured and may result in skin loss, blisters and ulcers.

Vascular disease is also a major problem in diabetes and especially affects very small blood vessels feeding the skin (microangiopathy). In this situation a doctor may find normal pulses in the feet because the arteries are unaffected. However other diabetic patients may also have narrowed arteries so that no pulse can be found in the feet (ischaemia). The lack of healthy blood flow may lead to ulceration. Wound healing is also impaired.

What are the signs and symptoms?

It is not unusual for patients to have had diabetic foot ulcers for some time before presenting to doctors because they are frequently painless.

Depending on severity diabetic foot ulcers may be rated between 0 and 3:

• 0: at risk foot with no ulceration
• 1: superficial ulceration with no infection
• 2: deep ulceration exposing tendons and joints
• 3: extensive ulceration or abscesses

Tissue around the ulcer may become black due to the lack of healthy blood flow to the foot. In severe cases partial or complete gangrene may occur.

Diabetic foot problems

Diabetics are also very prone to secondary infection of the ulcer (wound infection) and surrounding skin (cellulitis).

What is the management of diabetic foot ulcers?

Management of diabetic foot ulcers is primarily aimed at preventing them. Strategies include:

Optimise diabetes control to reduce neuropathic and vascular complications Preventive skin and nail care: examine the skin of both feet carefully and trim toenails regularly. See your doctor for advice if you have any skin problems such as athlete's foot, cracks or dermatitis.

Comfortable footwear: properly fitting soft shoes or made-to-measure insoles Once ulcers have developed, the cause should be determined. Is it neuropathic, vascular or both?

Neuropathic ulcers must be protected from further injury until they heal, and strenuous efforts must be made to avoid another ulcer by wearing correct footwear and frequent skin examination.

Vascular or ischaemic ulcers should be evaluated by a vascular surgeon to determine the extent of damage and whether surgery is necessary; in severe cases this may entail partial amputation of the limb.

Whatever the cause of the ulcer, any dead tissue of the surface should be debrided (removed) and the wound should be dressed to ensure a moist environment. Expert advice should be obtained, as the best dressing will depend on the type of ulcer and stage of healing.

Antibiotics may be prescribed if there is significant infection resulting in cellulitis.

Necrobiosis lipoidica

Necrobiosis lipoidica is a rare skin disorder, which can affect the shin of insulin dependent diabetics, although it may occur in non-diabetic subjects as well. The cause is unknown.

Typically, one or more tender yellowish brown patches develop slowly on the lower legs over several months. They may persist for years. They may be round, oval or an irregular shape. The centre of the patch becomes shiny, pale, thinned, with prominent blood vessels (telangiectasia). A minor injury to an established patch can cause it to ulcerate. This is often painless.

Treatment

Not all cases require treatment. The following are sometimes effective:

• Topical steroids, usually under a plastic occlusive dressing
• Intralesional steroid injections or steroid tablets
• Aspirin and dipyridamol combination
• Pentoxifylline tablets
• Oral cyclosporin
• Photochemotherapy (PUVA)

Diabetic dermopathy

The term diabetic dermopathy is used for round brown or purple slightly thinned patches seen on the shins of diabetic patients. Similar lesions are sometimes seen in non-diabetics. They occasionally affect the thighs and arms as well. Their cause is unknown. Treatment is not necessary or useful