Pathophysiology, clinical features and diagnosis of vascular disease affecting the limbs
Introduction
The term ‘peripheral arterial disease’ (PAD) is often employed to mean obstructive (‘obliterative’) disease of major lower limb arteries causing ischaemia. However, a range of vascular disorders can cause symptoms in upper and lower limbs, and a broader term ‘peripheral vascular disease’ (PVD) includes any disease of arteries, veins or lymphatics outside the heart. This chapter concentrates on lower limb vascular-related problems as they are much more common; upper limb symptoms are outlined in Table 40.5 (p. 488).
Vascular insufficiency of the limb (Table 40.1)
Table 40.1
Pathophysiology of arterial and venous insufficiency—the clinical consequences of vascular diseases affecting the lower limb*
*Aneurysms are covered in Chapter 42 and varicose veins and thrombophlebitis in Chapter 43.
Acute arterial insufficiency means inadequate arterial blood supply to a limb over hours or days. It may be caused by embolism into a normal artery, in which thrombus originating in the heart or other proximal site detaches and is swept distally until it lodges and obstructs the vessel. It can also occur by in situ thrombosis of an atherosclerotic plaque in lower limb arteries, by thrombosis of a popliteal aneurysm or by an aortic dissection extending into the lower limb vessels. Any disorder can manifest in several ways—see Table 40.2 for the various manifestations of popliteal aneurysm.
Symptoms and signs in the limb
An accurate initial diagnosis depends almost entirely on skilled and methodical clinical evaluation rather than on special investigations. Preliminary assessment notes obvious major risk factors (Table 40.3). Detailed history taking is covered in Table 40.4 and examination in Figure 40.1. In a suspected vascular case, the student or doctor tries to decide if the problem is arterial, venous or lymphatic, or has some other cause.
The principal symptoms and signs of vascular disease are pain, changes in skin texture, colour and temperature, tissue loss including ulceration, and swelling. The upper limb is affected by a largely different range of disorders with signs and symptoms with only a small overlap (see Table 40.5).
Pain
Most limb pain is due to musculoskeletal disorders such as arthritis or trauma rather than vascular disease. Where lower limb peripheral ischaemia is the working diagnosis, a full cardiovascular workup is needed (see Table 40.4 and Fig. 40.1).
• Lower limb—patients may have itching and aching with varicose veins, or have exercise-related pain or severe and constant pain caused by obliterative arterial disease. Where the history is short, acute ischaemia may be the cause
• Upper limb—vascular-related pain is uncommon. Aching and swelling may be caused by subclavian vein thrombosis. Claudication is rare and acute ischaemia is usually due to embolism. Thoracic outlet syndrome is also rare. The brachial plexus may be compressed as it passes between the clavicle and first rib (or extra cervical rib) causing nerve root symptoms. Even less commonly, the condition may cause arterial or venous obstruction at the thoracic outlet
Intermittent claudication
After a thorough history, only cauda equina claudication or pseudo claudication might be mistaken for ‘true’ claudication. This is caused by compression of the cauda equina in the spinal canal by central disc protrusion or canal stenosis. Lower limb pain is also brought on by exercise but there are important differences—see Table 40.6.
