Peripheral arterial disease (PAD) is a circulatory problem affecting blood vessels causing them to narrow which leads to reduced blood flow through the arteries. This typically reduces blood flow to the extremities manifesting as thigh or calf pain during walking or exertion [1]. Peripheral artery disease is a major risk factor for heart attack and stroke [2]. It usually involves atherosclerotic disease in the abdominal aorta, iliac, and femoral arteries.¹As a manifestation of systemic atherosclerosis, PAD is associated with greatly increased cardiovascular morbidity and mortality and impairment in quality of life [3]. Generally speaking, the presence of symptoms in PAD depends on the metabolic demands of the ischaemic tissue during exercise, the degree of collateral circulation and the size and location of the affected artery [4]. Walking pain from PAD is referred to as intermittent claudication which means “to limp.” Many patients with PAD have either no symptoms or atypical complaints that do not strictly conform to the definition of claudication. Others may develop limb-threatening compromise of blood flow, necessitating emergent surgery [1]. PAD has clinical significance as it is a marker of systemic atherosclerosis.

Anatomical Background

The abdominal aorta bifurcates at the level of fourth lumbar vertebra into two common iliac arteries that are large elastic arteries about 5 cm in length passing downward and laterally. The common iliac artery divides at the level of lumbosacral intervertebral disc, anterior to sacroiliac joint into external and internal iliac arteries [5-6]. Microscopically, the innermost layer of arterial wall is tunica intima made up of an endothelium, resting on a basal lamina, and a subendothelial connective tissue layer. The tunica media contains muscle cells, elastic fibres and collagen. The tunica adventitia is the outer coat consists of connective tissue, nerves and vessel capillaries [1]. Thickening of the intima progresses with age and is more marked in the distal than in the proximal segment of the aorta leading to narrowing of arterial lumen [5]. Arterial stenosis or occlusion is commonly caused by atheroma but can occur acutely as a result of emboli or trauma. The lower limb stenosis presents as claudication, rest pain and gangrene with severity of the symptoms related to the size of the vessel occluded and the alternative routes (collaterals) available for blood flow [7].

Case Presentation

A 57 years old male patient presented with pain in calf region and weakness of right leg for one year. The patient was chronic smoker for past 30 years. The pain and weakness was felt on walking and got relieved on rest. The intermittent claudication distance was 150 metres. The right lower limb had absent peripheral pulses. Ultrasound doppler suggested of more than 50% stenosis of right common iliac artery (CIA) near aortic bifurcation with reduced monophasic flow velocities in downstream arteries. CT Angiogram (Figure 1) showed eccentric circumferential mural thickening of the right CIA extending upto its bifurcation and causing 50-70% luminal narrowing. Mild mural thickening was also seen in left CIA with 30-40% narrowing. Focal eccentric mural thickening was also noted in mid left superficial femoral artery causing 50% stenosis of lumen. The remaining arteries of both the lower limbs were normal in calibre. Endovascular stenting of iliac arteries was done, postoperative medications were given and patient was advised to follow lifestyle modifications along with complete cessation of smoking [8-10].

Figure 1: 3D CT Angiography of the Abdominal Aorta and Lower Limb Arteries

The natural history of arteriosclerosis involves an intimal plaque that progressively develops until it eventually causes a significant flow limiting occlusion of the vessel and reduction of blood supply relative to demand. Arteriosclerosis is a systemic disorder affecting the major circulations, with the intimal plaque occurring segmentally in multiple locations [11]. PAD usually affects persons of age more than 40 years but it has been reported in young cases where there is family history of PAD and smoking. The goals of treatment include reducing the symptom of intermittent claudication, improving mobility and quality of life, and halting the progression of atherosclerosis by medications, lifestyle modifications and endovascular stenting. With continued smoking, the placement of stents in the patient’s vessels may induce thrombosis.

The hemodynamic consequences of atherosclerosis depend on the degree of arterial narrowing. A 50% decrease in vessel diameter corresponds to a 75% loss of cross-sectional area which is usually considered flow limiting. Iliac occlusive disease accounts for approximately one third of symptomatic lower-extremity occlusive arterial lesions, while two thirds are located infrainguinally. About four percent of patients with intermittent claudication require intervention.Chronic iliac artery occlusions are primary indications for stent placement. Percutaneous transluminal angioplasty (PTA) has proved very successful in dilating the iliac arteries but endovascular stenting has shown excellent results in the aorto-iliac segment (>90% success) and good results in the superficial femoral segment (90% success and 60–80% patency at 2y) [12]. The anatomical knowledge of arterial supply of lower limb and its collaterals is very important for full assessment of arterial disease and appropriate management by the vascular surgeons.

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