What is an arterial ulcer?
An ulcer is an area of full-thickness skin breakdown. An arterial ulcer is due to inadequate blood supply to the affected area. Arterial ulcers tend to occur on the lower legs and feet, and may be acute, recurrent or chronic. Other causes of leg ulceration include venous disease, diabetes, pressure injury, skin cancer and rare causes, such as vasculitis and pyoderma gangrenosum. Ulcers may have multiple contributing factors; these ‘mixed ulcers’ constitute roughly 15% of all leg ulcers.
Arterial ulcers are also known as arterial leg ulcers and ischaemic ulcers.
Who gets arterial ulcers?
Certain lifestyle factors and medical conditions have been associated with the development of arterial ulcers. These include:
- High blood fat and cholesterol
- High blood pressure
- Renal failure
- Rheumatoid arthritis
- Clotting and circulation disorders
- Other arterial disease, such as heart disease, cerebrovascular disease and peripheral vascular disease.
What causes arterial ulcers?
Arterial ulcers are caused by arterial insufficiency; that is, inadequate delivery of oxygen and nutrient-rich blood to the tissues. Arterial insufficiency is caused by high blood pressure and narrowing of the arteries due to atherosclerosis. Atherosclerosis is due to deposits of circulating lipids at the sites of damaged vessel walls as a result of the effects of smoking and high blood pressure. These deposits partially occlude the artery, resulting in reduced blood flow to tissues.
- Most often, an arterial ulcer develops following a minor injury that is slow to heal due to the poor blood supply to the wound.
- In severe arterial disease, spontaneous cell death may cause skin breakdown without a precipitating injury.
- Alternatively, cholesterol deposits lining the blood vessel walls may break off and become lodged in smaller vessels downstream, causing a sudden and complete blockage in flow; this process is called embolic occlusion.
What are the clinical features of arterial ulcers?
Distinguishing features of arterial ulcers include:
- Located on the lower legs and tops of the feet or toes
- A tendency to be painful, particularly at night
- A symmetrical shape with well-defined borders, often described as having a 'punched-out appearance'
- Minimal bleeding when touched or knocked
- Cool, pale or bluish surrounding skin that appears shiny
- Loss of leg hair
- Faint or absent ankle pulses.
Other symptoms of arterial insufficiency may also be present, such as:
- Cramping pains in the buttocks and back of the legs during exercise, relieved by rest (intermittent claudication); this is due to insufficient oxygen supply to meet the increased needs of exercising muscle
- Burning leg or foot pain at rest, which is relieved by lowering the foot and made worse by elevating it.
How are arterial ulcers diagnosed?
The underlying cause for a leg ulcer is diagnosed by taking a thorough patient history and a careful examination. Bedside tests include:
- Capillary refill time — this is the time taken in seconds for small blood vessels in the skin surface (eg, in the toe) to fill with blood after they are compressed. A prolonged capillary refill time may indicate arterial insufficiency in a patient with a lower limb ulcer, but it is a non-specific sign.
- A Buerger test — this involves having the patient lie flat and raising the leg 45 degrees above horizontal for 1 minute. A positive test suggestive of arterial disease is marked by the patient's foot turning pale when elevated and subsequently becoming bright red when lowered below the bed.
- Ankle Brachial Pressure Index (ABPI) — this is where a Doppler probe is used to measure the blood pressure in both the ankle and arm. If the ratio of these two values is < 0.9, arterial disease is likely. A value of ≤ 0.5 suggests severe disease.
- Transcutaneous oximetry — this is a measurement of the skin oxygen content around a wound. Measurements < 40 mmHg indicate vascular insufficiency and < 20 mmHg indicates severe insufficiency.
What is the treatment for arterial ulcers?
The treatment for arterial ulcers involves addressing the relevant factors contributing to arterial insufficiency and subsequent ulcer development in an individual. This may involve:
- Lifestyle changes, such as stopping smoking and change of diet in order to reduce blood lipid and cholesterol levels or control blood sugar
- Wound care — keeping the ulcer clean and moist by regularly changing wound dressings and physical or chemical debridement (removing areas of dead tissue)
- Treating wound infection — it should be noted that although bacteria colonise nearly all leg ulcers, systemic antibiotics are not required unless clinical signs of infection are present.
Signs that a venous ulcer may require treatment with antibiotics include:
- Redness and swelling of the surrounding skin
- Increasing warmth
- Increasing pain
- Increasing wound size
- Increasing discharge from the wound, especially pus
An arterial ulcer can be repaired by skin grafting (where a thin piece of skin is taken from another site, usually the upper thigh, and placed over the wound). A skin flap is an alternative way to cover the wound.
The surgical revascularisation of a limb aims to restore blood flow either by bypassing or angioplasty (re-opening) of narrowed vessels. This improves the healing of an ischaemic ulcer by restoring oxygen and nutrient supply to the tissue.