Understanding diabetic foot ulcers 2: Diagnosis and care (2024)

The diagnosis of a diabetic foot ulcer requires careful examination of the patient’s feet. This includes the top (dorsum), sole (planta) and sides of both feet, areas between the toes (interdigital), around the nails and the back of heels. Although neuropathic and neuroischaemic foot ulcers present at typical sites and display certain characteristics (see part 1), there may be atypical presentation.

INSPECTION

Hard skin and callused areas are signs that high pressures are occurring. If a callus is not reduced, the skin itself becomes hard enough to cause injury and the skin breaks down beneath the callus and ulcerates.

At this stage there may be no external sign of ulceration visible to the patient. However, close inspection of callused areas may alert a healthcare professional to imminent ulceration. Skin becomes discoloured in various ways. Sometimes a yellowish, halo-like appearance occurs and occasionally there will be signs of blood staining within the skin. With ischaemic ulcers, the skin usually reddens before ulcerating (Edmonds and Foster, 2005).

VASCULAR ASSESSMENT

Taking a good history from the patient may highlight symptoms that will aid clinical decision-making. For example, a patient with resting pain (indicating advanced disease) would require a more urgent vascular referral than a patient with stable intermittent claudication.

The initial practical step in assessing the contribution of ischaemia to a diabetic foot ulcer is palpation of two foot (pedal) pulses. The dorsalis pedis can be located by placing the fingers between the first and second toes and moving up to the area over the arch of the foot. The posterior tibial pulse is located in the hollow behind the medial malleolus. Absence of a pulse should be noted.

The next stage of vascular assessment is to perform an ankle brachial pressure index using doppler ultrasound.

NEUROLOGICAL ASSESSMENT

It is useful to begin a neurological assessment by taking a patient history with the emphasis on assessing pain sensation (Prodigy, 2006). For a useful practical guide, see Baker et al (2005).

Practitioners wishing to perform a neurological assessment should ensure that they have access to the relevant equipment. Tuning forks have been superseded by the neurothesiometer/biothesiometer. These are expensive items and not usually found in primary care.

It is likely that primary care practitioners will use the 10g monofilament. Although there is contention about the number of sites on the foot that should be tested with the 10g monofilament, my opinion is that it is better for a novice assessor to begin with the simplest method as described by the International Working Group on the Diabetic Foot (1999). This restricts the test to three sites on the forefoot. Inability of the patient to detect that the 10g monofilament is in contact with the foot signifies a neuropathic component to any presenting ulcer.

ADVICE FOR PREVENTION

Education

Patients need to be actively supported to self-manage their feet. This can involve daily checking of feet and awareness of the signs of infection (Berendt and Lipsky, 2003).

However, many patients at risk of diabetic foot ulcers will have other complications such as retinopathy, and this must be taken into account.

It may be necessary to engage relatives/carers in the self-management process (International Working Group on the Diabetic Foot, 1999).

Regular podiatry

Foot protection programmes (FPP) offering regular podiatry for patients who are at risk of foot ulceration, as well as footwear, hosiery checks and education have been shown to limit the effects of diabetic foot ulcers (McCabe et al, 1998). Health professionals in primary care have an important role to play in referring patients to FPPs and reinforcing the importance of regular attendance.

Skin care

Skin changes such as dry skin should be identified. Patients may need advice on the use of moisturising or emollient preparations.

Such products should not be applied between the toes as they can cause the skin in this area to become too moist. This may lead to splitting and fissuring, making it easy for bacteria to enter and the foot to become infected.

The effects of tinea pedis (athlete’s foot) can lead to breaks in the skin that become infected by bacteria. Tinea pedis should always be treated in people with neuropathy or ischaemia.

Footwear

In the early stages of diabetic foot disease when neuropathy or ischaemia are diagnosed but there is no ulceration, general footwear advice may be all that is required. This should be reinforced with leaflets (Edmonds and Foster, 2005). Details of local stockists can be useful. When deformity or ulceration have occurred referral to a podiatrist or orthotist for a specialist opinion is recommended (NICE, 2004).

PRINCIPLES OF TREATMENT

Treatment of diabetic foot ulcers depends on whether they are neuropathic or predominantly ischaemic. Detailed guidelines on treatment (Prodigy, 2006) recommend immediate referral to a multidisciplinary foot clinic. Basic principles of treatment include assessment for:

• Peripheral arterial disease;
• Infection;
• Pressure relief;
• Wound care;
• Blood glucose control;
• Education.

If tissue damage has occurred and the wound is non-healing or deteriorating, this increases the urgency of the referral. A pink or pale, painful, pulseless foot can indicate a critically ischaemic foot and hospital admission may be necessary (Prodigy, 2006). In patients with peripheral arterial disease, diabetic foot ulcers are at risk of rapid deterioration. This should be considered when deciding on treatment intervals or review appointments.

Infection

Infection in the diabetic foot already complicated by neuropathy or ischaemia will cause major tissue destruction if left untreated (Edmonds and Foster, 2005). An accurate appraisal of the wound and commencing appropriate treatment can often prevent a critically colonised wound from deteriorating into spreading infection.

PRESSURE RELIEF

Every attempt should be made to offload the ulcer and redistribute pressure away from the affected area. This often begins with reducing a callus using scalpel techniques. Callus contributes to increased pressure on the insensate foot (Steed et al, 1996). Other treatments vary from adapting patients’ own footwear to specialist plaster casts.

WOUND CARE

Tissue viability nurses are a source of advice on wound care products. There is a wide range of products available.

Many of the more interactive/advanced products have been of benefit to patient care but there remains a lack of robust evidence that one product is superior to another. Products used to treat diabetic foot ulcers should be chosen for their ability to:

• Protect against contamination of the wound by potential pathogens;
• Minimise bulk and reduce pressure;
• Handle wound exudate.

In neuropathic ulcers, drainage of wound exudate can be facilitated by debridement of the wound. Debridement of slough and necrotic tissue from the wound margins and within the wound bed reduces sites for micro-organisms and lessens the chances of infection.

Hyperglycaemia and wound healing

Hyperglycaemia affects many of the biochemical pathways of the body. The ability of an ulcer to progress through the phases of wound healing involves a number of complex cellular processes, actions and interactions.

Patients with continually high blood glucose levels have impaired white blood cell activity, which leads to delayed wound healing (Senior, 2000). Part of diabetic foot ulcer treatment should be aimed at optimal blood glucose control.

Education

Instruction in dressing technique is necessary if the patient is caring for a foot ulcer. It is important that both patient and healthcare professional recognise the signs of deterioration and infection and always check for these when re-dressing ulcers:

• Change in the colour of the foot, for example, redness signifying infection or blue/black signifying necrosis;
• Change in wound bed from viable tissue to friable granulation tissue or slough (European Wound Management Association, 2005);
• Swelling of the foot;
• Increased discharge or change in viscosity;
• Fever or flu-like symptoms.

CONCLUSION

Diabetic foot ulcers can be neuropathic in origin or predominantly ischaemic. The effects of neuropathy can be dry skin and callus formation, especially over areas of the foot subject to high walking pressures. Ischaemia leads to delayed healing.

Both neuropathic and ischaemic ulcers will deteriorate in the presence of infection, with serious consequences. Therefore it is important to diagnose diabetic foot ulcers early and involve all members of the multidisciplinary team in their treatment.