The medical history initiates the physician-patient relationship, guides the uncovering of relevant physical findings, facilitates appropriate vascular testing, and then assists treatment choices. Per one report, a skilled history can lead to the correct diagnosis 75 % of the time [1]. The most common presenting symptom for limb ischemia is pain, and knowing its severity, location, frequency, exacerbating, and/or relieving factors along with the duration assists in distinguishing vascular vs nonvascular leg discomfort.

A distinction must be made between chronic critical limb ischemia (cCLI) and acute critical limb ischemia (aCLI).aCLI is a medical emergency related to abrupt arterial occlusion which requires immediate treatment. The pathophysiology of cCLI is related to slowly progressive, inadequate arterial limb perfusion that is below the threshold needed to meet the metabolic demands of the limb, resulting in resting ischemia with pain, skin breakdown, and eventual tissue necrosis [2].

aCLI most commonly occurs due to embolism or in situ thrombosis . Arterial dissection or trauma can also cause aCLI but at a much lower rate. Unfortunately, the presenting symptoms do not predict the cause of aCLI. Patients can present with an asymptomatic loss of pulse, acute deterioration in previously stable claudication or as sudden onset of severe rest pain in the affected limb. These symptoms may develop over several days or over few hours. Acute arterial occlusion may result in any one or all of the notorious five “Ps”:

These manifestations typically occur due to lack of collateral blood flow and reestablishment of primary arterial flow in timely fashion is the key.

The pain in aCLI may be evanescent and pallor may quickly give way to cyanosis. This discomfort is very different than that of cCLI. For instance, it is not localized to the acral portion of the foot and is not affected by gravity. The pain is usually diffuse and can extend above the ankle in severe cases. It is usually of sudden onset and may quickly increase in intensity when caused by arterial emboli (Fig. 6.1). Patients can describe the feeling as being struck in the limb after which they feel weak. In case of arterial thrombosis, the pain develops less rapidly, but patient is aware of some change in their baseline status. The rapid peak in pain intensity is also absent in arterial thrombosis. However, in the case of massive arterial thrombosis where the limb is threatened, the pain quickly and unexpectedly changes in intensity. The pain may subside in intensity after the initial vasospasm subsides and collateral flow is recruited. Finally, the discomfort may completely resolve if the collateral supply is able to meet the functional demands of the foot or it may convert into the pain typically seen in cCLI patients.

Pulses are usually difficult to palpate since the majority of this patient population have preexisting peripheral arterial occlusive disease.

The sensory deficit may be minimal and can easily be missed early in the course of presentation. Patients may lose sensation of light touch, the ability to differentiate two points, and experience altered vibratory perception and proprioception before deep pain ensues. Loss of motor function may present very late in the process as the majority of foot movements are produced by muscles originating below the knee. It can be challenging to test for the motor function of the foot as these muscle groups may not be developed at baseline in many PAD patients. The tests that are generally advocated in evaluating the intrinsic foot muscles are the paper grip test and intrinsic positive test :

More objective testing can be performed in centers that have access to a handheld dynamometer. This instrument can measure toe flexor strength [5].

The persistence of pain, particularly if followed by numbness and/or weakness suggests the threat of limb loss.

Inability of the blood flow to meet the functional demands of tissue produces pain that has two very distinct characteristics: intermittent claudication and ischemic rest pain.

Intermittent claudication is discomfort associated with exercise that is relieved by rest. Depending on the anatomical location and extent of arterial occlusive disease, the patient may present with buttock, thigh, and/or calf claudication. Calf claudication is the most common presenting symptom and is reported as cramps in the calf that are brought on by walking. This should not be confused with nocturnal cramps that some elderly people manifest. These cramps have no known vascular origin and are thought to be the result of an exaggerated neuromuscular response to stretching. Chronic exertional compartment syndrome can also produce calf tightness provoked by exercise, but the distinguishing feature is that the patient is usually a younger athlete without atherosclerotic risk factors and large calf muscles. Increased muscle pressure due to impaired venous outflow is usually the cause and this pain is not relieved quickly by rest.

Thigh and buttock claudication is different than calf claudication as the exertional pain is much less pronounced. Instead, patients typically complain of an exertional ache or discomfort that is associated with weakness. Patients might say that their hip or thigh “gives out” or “tires” after they have walked a stereotypical distance. Thigh and buttock claudication may be somewhat similar to the pain of hip osteoarthritis, but the amount of exercise that provokes discomfort in osteoarthritis is variable; the pain does not subside promptly upon cessation of activity, and there is considerable day-to-day pain variability. Neurospinal compression may also cause exertional buttock and thigh pain, but the main differentiating feature from claudication is associated limb numbness and that the symptom complex can also be produced by prolonged standing. Additionally, the pain and numbness of neurospinal compression can also involve the perineum. Affected patients often relate their symptoms are improved with truncal flexion such as when they shop in the supermarket and lean on the shopping cart. However, straightening of the lumbar spine is likely to exacerbate their symptoms. Since patients presenting with lumbar neuroforaminal compression are often elderly, coexistent PAD with claudication can confound the diagnosis and it is paramount that the predominant complaints be matched to the disease. Treating mild arterial occlusive disease in this patient will not relieve their symptoms. Thigh claudication can also be part of the postthrombotic syndrome that usually occurs when the patient has history of ilio-femoral deep vein thrombosis (DVT ) and the collateral venous outflow fails to match the increased arterial inflow during exercise. The pain is often described as “bursting” or a severe tightness or heavy sensation that is relieved by cessation of exercise, but the improvement is not as rapid as in arterial claudication.