Fibromuscular Dysplasia


2.4.1 Basics

Arterial fibromuscular disease encompasses a heterogeneous group of nonatherosclerotic vascular occlusive and aneurysmal diseases. A principal forum of fibrodysplastic stenoses includes:

• Intimal fibroplasia

• Medial hyperplasia

• Medial fibroplasia

The first two are distinctly different pathological entities, whereas the latter two appear to represent a common disease in evolution. Compounding this classification are hypoplastic dysplastic vessels occurring as true developmental lesions. Various combinations of dysplastic lesions exist, as do other less easily categorized vessel wall derangements. It is also important to distinguish primary arterial fibrodysplasia from secondary disease found in vessels subjected to earlier inflammatory attacks, physical insults and other distinct disease entities. Anatomy

Fibromuscular disease affects the following:

• Renal arteries

• Extracranial and intracranial cerebral arteries

• Axillary, subclavian and brachial arteries

• Coeliac, superior mesenteric and inferior mesenteric arteries

• Iliac, femoral, popliteal, tibial and peroneal arteries

Venous involvement is extremely rare. There have been reports of the disease in superficial veins of the lower extremities as well as in the renal veins. However, the existence of primary venous fibrodysplasia is controversial. Physiology, Pathophysiology Renal Arteries

Renal artery fibromuscular disease was first described in 1938 and is second only to atherosclerosis as the most common cause of surgically correctable hypertension [15].

Intimal Fibroplasia

• Intimal fibroplasia of the renal artery affects male and female patients with equal frequency.

• It accounts for approximately 5% of all dysplastic renal artery stenoses and is observed in infants, adolescents and young adults.

• Most often it affects the main renal artery, usually occurring as a smooth focal stenosis.

• Segmental vessel involvement is a more uncommon manifestation of intimal disease [13].

Intimal Hyperplasia

• Once a haemodynamically important arterial stenosis develops, progression of intimal hyperplasia appears a likely consequence of abnormal blood flow, even if the initiating aetiological factors have resolved.

• The specific cellular messengers responsible for this tissue proliferation have not been identified.

• Intimal lesions appear to progress at a much slower rate than do medial fibroplastic stenoses.

Medial Hyperplasia

• Medial hyperplasia without associated fibrosis is an unusual cause of renal artery stenosis.

• In fact, the existence of this particular dysplastic disease is subject to discussion.

• It has been most often described in women during their fourth and fifth decades of life.

• If indeed this type of lesion actually exists, it accounts for fewer than 1% of dysplastic renovascular lesions.

• Focal stenoses caused by medial hyperplasia usually involve the mid-portion of the renal artery, not its branching or segmental vessels.

Medial Fibrodysplasia

• Medial fibrodysplasia accounts for nearly 85% of dys-plastic renovascular disease.

• More than 90% of patients with medial fibrodysplasia are female.

• The morphological appearance of renal artery medial fibrodysplasia ranges from a solitary focal stenosis to its more common presentation as a series of stenoses with intervening aneurysmal outpouchings.

• The latter, which cause a string-of-beads appearance, has not been observed in female patients before men-arche, with the exception of a single case report.

• Medial fibrodysplasia most commonly affects the distal main renal artery, with extensions into first-order segmental branches occurring in approximately 25% of cases.

• Progression of medial fibrodysplasia appears to occur in 12-66% of patients with main renal artery lesions.

• Progression is thought to be more likely to affect pre-menopausal women, but some authors have noted no differences related to age.

• Hypertension develops in approximately 26% of cases.

• In 18% of cases the disease progressed to complete occlusion, although acute changes are uncommon.

• Two histological forms of renal artery medial fibrodysplasia are well recognized: the first is evident by disease of the outer media (peripheral form) and the second by disease throughout the entire media (diffuse form).

• The second form is noted twice as often as the former.

• The peripheral form is usually encountered in younger patients.

• This observation lends support to the tenet that both forms represent the same disease process.

Perimedial Dysplasia

• Perimedial dysplasia is the dominant abnormality affecting approximately 10% of dysplastic renal arteries.

• It may coexist with medial fibrodysplasia.

• Most patients with this type of disease are female in their fourth or fifth decade of life, and these lesions present as either focal stenoses or multiple constrictions involving the midportion of the main renal artery without mural aneurysms.

• Excessive elastic tissue at the junction of the media and the adventitia is the distinguishing feature of perimedial dysplasia.

Extracranial and Intracranial Cerebral Arteries: Carotid and Vertebral Arteries

Arterial fibrodysplasia in these arteries is a clinical entity of potential importance, although controversy exists beyond the simple assertion that certain lesions cause symptoms of cerebral ischaemia.


• The precise incidence of this disease is poorly defined, although lesions of the extracranial internal carotid artery (ECICA) were noted in 0.42% of 3600 patients undergoing cerebral arteriograms [3].

• This finding was identical to the 0.4% reported from the Mayo Clinic [16].

• Many of these examinations were for suspected cere-brovascular disease and thus the true frequency of ECICA fibrodysplasia in the general population would be expected to be lower.

• Unfortunately the much lower 0.02% incidence of the disease among necropsy examination is likely to be too low, because of the uncommon removal of distal segments of the ECICA during routine autopsies.

• Vertebral artery disease is even less common, having been noted in approximately 20% of patients manifesting ECICA fibrodysplasia.

Aetiology/Pathology of Carotid Artery Disease

• Various pathologic processes have been categorized as ECICA fibrodysplasia.

• The two major subgroups include: (1) intimal fibrodysplasia and (2) medial fibrodysplasia.

• The intimal form is often associated with elongation, kinking and coiling of the carotid artery and appears for the most part to be a secondary rather than a primary dysplastic process.

• This seems to be particularly true of intracranial intimal fibroplasias.

• Occasional atypical lesions appear as isolated webs of the ECICA.

• Medial fibrodysplasia of the ECICA was first documented arteriographically and histologically more than three decades ago.

• These lesions invariably occur in female patients.

• Medial fibrodysplasia of the ECICA typically involves a segment of 2-6 cm of the mid-carotid artery adjacent to the second and third cervical vertebrae.

• The serial stenoses are often evident on examination of the external surface.

• Bilateral disease has been reported to occur in 35-85% of patients with these lesions, with an average incidence of approximately 65%.

• Involvement of the ECICA at its origin with the classic form of this dysplastic lesion has not been described.

• Carotid arteries affected by medial fibrodysplasia are often elongated, and kinking occurs in approximately 5% of cases.

• Typical medial fibrodysplastic lesions of the anterior intracranial arteries are uncommon.

• Similar lesions of the external carotid artery or its branches have been reported, but they are exceedingly rare.

Aetiology/Pathology of Vertebral Artery Disease

• Vertebral artery disease, in the form of either multiple stenoses or nonocclusive mural aneurysms, has often been overlooked.

• These lesions develop in the lower vertebral artery at the level of the fifth cervical vertebra, or higher at the level of the second vertebra.

• They exhibit marked irregularities and are often accompanied by eccentric mural aneurysms, but they do not manifest the typical string-of-beads appearance noted in other muscular vessels affected with medial fibrodysplasia.

• Dysplastic lesions of the basilar artery are an uncommon form of intracranial medial fibrodysplasia.

Involvement of Other Vessels

• Noncerebrovascular medial fibrodysplasia occurs in many patients with ECICA lesions.

• Renal artery involvement affects as many as 25% of these individuals.

• The frequency of simultaneous ECICA and renal artery dysplasia may be even higher, and it has been reported to be 50% in patients who underwent arteriography assessments of both vessels.

• Similar lesions have also been observed in the external iliac and superior mesenteric arteries.


• Coexistent intracranial aneurysms have been documented in 12-25% of patients with ECICA medial fibrodysplasia.

• Solitary intracranial aneurysms are present in 80% of these patients, with multiple aneurysms occurring in the remaining 20% of cases.

• A meta-analysis of 18 series, excluding those with subarachnoid haemorrhage, revealed a 7.3% prevalence of cerebral aneurysms in patients with carotid or vertebral fibrodysplasia.

• Although intracranial arteries are occasionally the site of dysplastic disease, aneurysms do not develop in the involved vessel. Instead they appear to evolve as a generalized dysplastic arteriopathy, manifested by weakening in arterial branches, which increases the likelihood of berry aneurysm formation. These aneurysms tend to occur on the same side as the ECICA disease.

• The anatomical distribution of aneurysms in patients with medial fibrodysplasia is the same as that in patients not affected with dysplastic ECICA.

• Hypertension may contribute to the evolution of these aneurysms, but it has not been identified as a dominant factor in their pathogenesis.


• Complications occurring with medial fibrodysplasia of the ECICA appear to be related to:

• Encroachment on the lumen that causes flow reduction.

• Occasional collection of thrombi within the cul-de-sacs.

• Potential distal embolization.

• Dissections and rupture with arteriovenous fistula formation.

• The precise incidence of these complications has not been determined, but they appear to occur in fewer than 10% of cases.

• Frequently, dissection obliterates clear evidence of the underlying fibrodysplastic process, and many individuals experiencing this complication are thought to have suffered from spontaneous dissections.

• Progression of ECICA medial fibrodysplasia may approach 30%, but the exact rate has yet to be defined.

• Complications occurring with medial fibrodysplasia of the vertebral arteries are rare and are usually related to thromboembolism or dissections.

Iliac, Femoral, Popliteal and Tibial Arteries

• The third vessel most commonly affected with medial fibrodysplasia is the external iliac artery.

• Serial stenoses with intervening mural aneurysms typically affect the proximal third of this vessel.

• These lesions are similar to those of the renal and ECICA vessels and may in fact occur in patients with other lesions.

• Fibroproliferative processes primarily involve the medial tissue adjacent to areas of relative thinning.

• Occasional fibrodysplastic lesions of the iliac vessels appear as solitary dilatations.

• Complications of external iliac artery fibrodysplasia usually reflect encroachment on the lumen, with restriction of blood flow or the development of micro-thrombi that embolize peripherally.

• Acute dissection may occur with these lesions, but it is not common.

• Although exceedingly rare, similar lesions reflecting the systemic nature of medial fibrodysplasia have been reported to affect the femoral, popliteal and tibial vessels of the lower extremity.

• In some instances, these extremity lesions have thrombosed; in others they have been associated with aneurysmal changes [19].

Axillary, Subclavian and Brachial Arteries

• The most common dysplastic lesion affecting upper extremity vessels appear to be intimal hyperplasia, which is usually manifested by smooth focal or long tubular stenoses.

• There is a slight predominance of women among patients with these dysplastic lesions [7].

• Dysplastic disease compatible with medial fibrodys-plasia, with characteristic dilatations and constrictions or histological confirmation of this form of dysplasia, may affect the subclavian, brachial, radial and ulnar arteries.

• However, these particular lesions of the upper extremity arteries are too uncommon to be rigorously classified as to type and clinical importance.

Splanchnic Arteries: Coeliac and Mesenteric

Intimal Fibroplasia

• Intimal fibroplasia may affect the origins of the three principal splanchnic vessels: coeliac, superior and inferior mesenteric.

• The basis of these lesions is unknown, but this fibrodysplasia may reflect a secondary phenomenon occurring in developmentally narrowed vessels.

• Ostial fibrodysplastic lesions are quite common in patients with intestinal angina and often exhibit associated atherosclerotic changes.

• Intimal fibroplasias tend to occur more often in women than in men, with nearly equal involvement of the coeliac and superior mesenteric artery (SMA) [20].

Medial Fibrodysplasia

• Medial fibrodysplasia is rare within the splanchnic circulation, although histological evidence of it has been reported.

• When present, this form of splanchnic vascular disease is often associated with similar renal or carotid lesions.

• Histological evidence of medial dysplasia is also common among patients with splenic artery aneurysms. In fact the development of these aneurysms may be a reflection of compromised vascular integrity due to the disruptive dysplastic process.

• Similar aneurysms have been noted in other splanchnic vessels, including the SMA.

• The proximal SMA may exhibit medial fibrodysplastic occlusive disease a few centimetres beyond its origin as it exits beneath the pancreas over the top of the highest point of the duodenum.

Other Vessels

• Most other vessels affected with dysplastic disease involve intimal fibroplasia. Exceptions are: medial fibro-dysplasia also affecting coronary arteries and exhibiting dissections as well as thromboses.

• Other dysplastic lesions have been noted, among patients ranging from neonates to the elderly, in large arteries the size of the aorta to very small vessels such as the coronary sinus node artery.

• It is unlikely that the changes in these vessels represent a systemic arteritis in its active stage, although they may represent an end stage of an earlier arteritis.

• Again, experience with these rare forms of arterial dysplasia is so meagre as to preclude rendering of any firm conclusions about their aetiology or clinical relevance. Organ-related Questions

For renal fibroplasia, organ-related questions regarding the special case history include the search for:

• arterial hypertension (headaches, dizziness, tinnitus)

• arterial infarction (sudden severe pain) or

• renal insufficiency.

For cerebrovascular fibroplasia, organ-related questions regarding the special case history include the search for symptoms of:

• transient ischemic attacks

• carotid dissection (stroke).

For fibroplasia of the arteries of the lower extremities, organ-related questions regarding the special case history include the search for:

• intermittent claudication

• blue toe syndrome resultant from acute thromboem-bolism. Principles of Clinical Examination

Clinical examination includes a search for signs of arterial hypertension:

• measurement of arterial blood pressure

• fundoscopy for lesions of the retinal vessels.

Carotid Disease

• Neurological examination for neurological deficits from a previous event (stroke), Horner's syndrome and cranial nerve palsies.

• Intracranial or extracranial cerebrovascular fibromus-cular dysplasia may be discovered incidentally as the cause of a cervical bruit.

Lower Extremity Disease

• Palpation of peripheral arterial pulses.

• Examination of capillary circulation and critical limb ischaemia. Technical Diagnostic Procedures

Renal Fibromuscular Disease

• Duplex imaging of the renal arteries can accurately detect elevated blood-flow velocities, especially in the distant portion of the arteries, which are most often due to fibromuscular dysplasia.

• Computed tomography may play an important part in the diagnosis and follow-up of renal artery fibromus-cular dysplasia, but is inferior to catheter-based angiography at present [8, 9].

Cerebrovascular Fibromuscular Dysplasia

• Duplex ultrasonography of the carotid arteries may demonstrate irregular patterns of stenosis and aneu-rysm.

• Since fibromuscular dysplasia affects the middle and distal portions of the carotid and vertebral arteries, it may be difficult to visualize these lesions by means of Duplex ultrasound, which has a lower sensitivity than angiography.

Lower Extremity Fibromuscular Arterial Disease

• Duplex ultrasonography may demonstrate high velocities due to arterial stenosis or give a low ankle/brachial blood pressure index. Organ-specific Radiology

Renal Artery Disease

• Catheter-based angiography remains the most accurate method for diagnosing fibromuscular dysplasia.

• Although captopril renography was once the noninvasive diagnostic method of choice for patients with renal artery disease, it has now been relegated to use in secondary screening, since the quality of noninvasive methods is so high.

• The role of magnetic resonance angiography in the evaluation of the disease remains uncertain, since its resolution remains inferior to that of catheter angiog-raphy.

Cerebrovascular Disease

• Angiography has a higher resolution than Duplex ul-trasonography for the detection of cerebrovascular fi-bromuscular disease.

• There has been little experience with computed tomography or magnetic resonance angiography, but the latter should be performed to rule out the presence of intracranial aneurysms in patients with dysplasia.

Lower Extremity Disease

• Digital angiogram is the method of choice depicting fibromuscular lesions in the lower extremities.

2.4.2 Organ-related Diseases

• Arterial hypertension

• Cerebrovascular insufficiency

• Lower extremity insufficiency

• Splanchnic ischaemia. Synonyms

• Arterial dysplasia

• Arterial fibrodysplasia

• Arterial fibromuscular dysplasia (FMD). Definition

• Nonatheromatous noninflammatory vascular disease most commonly affecting the renal and internal carotid arteries, but described in almost every arterial bed in the body. Epidemiology/Aetiology

• The precise incidence of renal artery disease in the general population is unknown, but it is less than 0.5%.

• The frequency among black hypertensive patients appears to be even lower.

• Renal artery dysplasia is second only to atherosclerosis as the most common cause of surgically correctable hypertension.

• The pathogenesis of medial fibrodysplasia and perimedial dysplasia has been the subject of much speculation.

• Hormonal effects on smooth muscle, mechanical stresses on the vessel wall and a peculiar distribution of vasa vasorum in arteries exhibiting these lesions are all considered to be contributing factors. The exact relation of these factors to each other, or their association with other unrecognized pathogenetic mechanisms, remains unknown.

• Because of the familial nature of the disease, a genetic-related autosomal dominant aetiology has been suggested, but not established. Genetic factors may play a part in the development of FMD, since the disease is more common among the first-degree relatives of patients with FMD of the renal arteries and among persons with type-I angiotensin-converting enzyme (ACE-I) [4, 10].

• Hormonal influences seem likely in view of the unusual female predilection pertaining to arterial dysplasia. More than 95% of patients exhibiting medial and perimedial disease are women.

• Pregnancy is not an obvious aetiological factor in arterial fibrodysplasia.

• Also no association between antiovulants or oral contraceptives and the disease was demonstrated.

• It is speculated that physiological preconditioning of vascular smooth muscle cells to a secretory state by normal circulating oestrogens associated with the reproductive cycle may account for the more frequent occurrence of medial dysplastic disease in females.

• Unusual physical stresses due to ptosis of the kidneys may be associated with fibrodysplastic changes in the renal arteries.

• A final aetiological factor may be related to mural ischaemia in dysplastic arteries. The renal, extracranial internal carotid and external iliac arteries are the three vessels most likely to develop medial fibrodysplasia. The latter two arteries, in particular, have relatively few branches compared with similar-sized vessels. Compromise of vasa vasorum in these vessels, in which scarcity of these nutrient vessels already exists, may lead to significant mural ischaemia.

• Cigarette smoking has been implicated as an important aetiological factor in this disease, although the mechanism has not been defined.

• Medial fibrodysplasia of the ECICA was first documented arteriographically and histologically more than three decades ago. These lesions invariably occur in female patients, with a mean patient age at the time of recognition being approximately 55 years. Similarly, these lesions, like those of the renal artery, have been infrequently recognized among Afro-American patients.

• The pathogenesis of ECICA medial fibrodysplasia is poorly understood, but it appears to be similar to that occurring in the renal vessels. The role of mural ischaemia may be greater because very few muscular branches have origins from the extracranial portion of the internal carotid artery, thus reducing the number of intrinsic vasa vasorum in this vessel. Certainly, unusual traction or stretch stresses that occur with hyperextension and rotation of the neck appear to be another dominant factor in the development of these lesions.

• Trauma has been cited as an aetiological factor in instances of vertebral artery fibrodysplasia. In fact, unrecognized adventitial bleeding due to vertebral artery injury during birth may be important in the later development of these lesions.

• Most individuals with medial fibrodysplasia of the iliac vessels have been women in their fifth or sixth decade of life, about 10 years older than those presenting with similar renovascular disease. The aetiology of dysplastic lesions of the iliac and femoral arteries may be related more to a paucity of vasa vasorum than to any physical stretch or traction stresses.

• The incidence of external iliac artery fibrodysplasia in the general population is unknown, but this condition has been reported to occur in 1-6% of patients with renal artery fibrodysplasia.

• Intimal fibroplasia of the external iliac artery, as well as that of the femoral, popliteal and tibial vessels is usually considered to be a secondary pathological phenomenon rather than a primary aetiological process. Although most instances of intimal disease affecting these vessels may be the consequence of prior trauma, the result of thromboembolism with recanalization of intraluminal thrombus, or the sequela of prior arthritis, certain cases appear to represent primary intimal hyperplasia.

• The most common dysplastic lesion affecting upper extremity vessels appears to be intimal hyperplasia. There is a slight predominance of women. Speculation exists as to the aetiology, although the most likely underlying cause is related to an arteritis. Other intimal fibroplastic lesions affecting the subclavian and axillary vessels may be a consequence of injury (that associated with repetitive subclavian trauma at the thoracic outlet) or of abnormal flow associated with anatomical bands causing vascular narrowing.

• Dysplastic disease compatible with medial fibroplasias with characteristic dilatations and constrictions may affect the subclavian, brachial and radial and ulnar arteries. However, these lesions are common.

• Characteristic medial fibrodysplasia is rare within the splanchnic circulation. The basis of these lesions has not been established, although unusual stretch forces at the root of the mesentery may contribute to dysplastic changes. Symptoms

• Hypertension may be present in renal disease.

• Cerebrovascular fibromuscular dysplasia may be asymptomatic or associated with a variety of nonspecific symptoms, including headache, tinnitus, vertigo, light-headedness and syncope.

• The more specific neurological syndromes of transient ischaemic attack, amaurosis fugax, stroke, Horner's syndrome and cranial nerve palsies may be the first presentation of FMD involving the carotid or vertebral arteries.

• In lower extremity disease intermittent claudication is the common symptom, but critical limb ischaemia or peripheral microembolism may also present.

• Intestinal angina may occur when at least two of the major mesenteric arteries are obstructed. In unusual cases, the stenosis progresses to total occlusion, leading to acute intestinal ischaemia.

• In upper extremity disease, patients experience weakness, paraesthesias, or claudication in their arms.

Imaging and Laboratory Tests

Additional useful diagnostic procedures include:

• Duplex ultrasonography

• Computed tomography

• Catheter-based digital angiography

• Magnetic resonance angiography

• Plasma renin activity and angiotensin II determination for evaluation of renal sufficiency. Complications Renal Disease

• Hypertension (cerebral haemorrhage or cardiac insufficiency).

Cerebrovascular Disease

• Rupture of an intracranial aneurysm.

• Cerebral embolism originating from intravascular thrombi in stenotic regions.

Lower Extremity Disease

• Peripheral atheroembolism or critical limb ischaemia.

Splanchnic Disease

• Intestinal ischaemia or necrosis. Diagnosis


• Inspection for the presence of neurological deficits in cerebrovascular disease or the presence of ischaemia of the lower extremities.

• Palpation of peripheral arterial pulses.

• Auscultation for bruits in the neck or in the abdomen or femoral areas.

• Arterial pressure measurements. Treatment Conservative Treatment

• Pharmacological therapy for hypertension in patients with renal artery FMD should follow the Recommended European standard therapeutic steps.

• Clopidogrel (75 mg daily) or acetylsalicylic acid (ASA) alone or in combination could be given for cerebro-vascular FMD to prevent stroke. These drugs may also help in peripheral arterial disease.

Recommended European Standard Surgical Procedures

• Revascularization should be considered for certain types of hypertensive patients:

• Those with a recent onset of hypertension in whom the goal is to cure the hypertension.

• Those in whom blood pressure control has proved difficult despite the use of a comprehensive antihy-pertensive regimen.

• Those with an intolerance of antihypertensive medications.

• Those whose blood pressure has been difficult to control because of noncompliance.

• Those who have lost renal volume because of isch-aemic nephropathy.

• Before the advent of percutaneous transluminal angioplasty (PTA), surgical revascularization was the primary therapeutic alternative for patients with refractory hypertension.

• Overall, the technical success rates ranged from 89% to 97%.

• Hypertension was cured in 33-63% of patients, improved in 24-57% and failed to improve in 3-33%.

• A longer duration of hypertension, concomitant atherosclerotic disease and complex branch-vessel repair all adversely affect the results of surgical revasculariza-tion.

• Although there are no available prospective data demonstrating the superiority of PTA over surgical revas-cularization, the percutaneous approach has emerged as the mainstay of treatment for patients with FMD who meet the criteria for intervention.

• Although stents have been used extensively for the treatment of atherosclerotic renal artery stenosis, the use of stents for FMD has been reserved as a "bailout" procedure in cases in which there are suboptimal results with balloon angioplasty or in which renal artery dissection occurs.

• There is no role for stent implantation as a primary treatment for FMD, since angioplasty alone is quite efficient [1, 14, 18].

• For patients with aneurysms or complex occlusive lesions of the renal artery, renal autotransplantation (RAT) is a well-established alternative to PTA in cases where catheter-based techniques are contraindicated [6].

• Similarly, before the use of PTA became widespread, surgery was the mainstay of therapy for patients with symptomatic cerebrovascular FMD. The surgical techniques used depended on the type of lesion and its location, but the most widely used procedure was graduated intraluminal dilatation.

• Other procedures that have been used include intraoperative PTA, placement of a polytetrafluoroethylene-covered endograft, resection of the diseased segment and primary anastomosis, grafting of autogenous sa-phenous vein, resection of the aneurysm and carotid endarterectomy.

• During the last 10 years, PTA has become the preferred treatment for symptomatic cerebrovascular FMD. There have been no randomized, controlled trials comparing surgery with balloon angioplasty in this condition.

• The use of cerebral protection devices may reduce the frequency of ischaemic neurological events during stenting of the carotid artery [12].

• For symptomatic FMD in the arms or legs, treatment consists of PTA.

• Treatment options for FMD of the visceral arteries include PTA and surgical by-pass. Differential Diagnosis

• Atherosclerosis generally occurs at the origin or proximal portion of the artery in older patients with typical cardiovascular risk factors.

• Ehlers-Danlos syndrome (type IV) has been associated with medial fibroplasias in patients with multiple aneurysms in addition to the typical angiographic findings of FMD. There have been isolated reports of FMD associated with Alport's syndrome, phaeochro-mocytoma, Marfan's syndrome and Takayasu's arteri-tis.

• Vasculitis is an inflammatory process, associated with anaemia, thrombocytopaenia or abnormalities of acute-phase reactants. Large-vessel vasculitis may occur in the absence of changes in acute-phase reac-tants in up to 40% of cases. When histological proof or markers of inflammation are not available, it may be difficult to distinguish between these entities, because their angiographic appearance may be similar.

• Although MR angiography may show wall thickening in patients with giant-cell arteritis or Takayasu's arte-ritis, it is not useful in patients with renal or intestinal FMD, because the resolution of MR angiography is inadequate for the visualization of branch-vessel involvement.

• In some cases intravascular ultrasound may help to distinguish FMD from vasculitis. Prognosis

• Although the loss of renal mass occurs in up to 63% of patients with renal artery FMD, renal failure is rare in these patients.

• Multiple-organ involvement in FMD is particularly troublesome, since ischaemia may be associated with increased risk of complications and death. Exemplary Surgical Procedures

Procedure 1

Aortorenal By-pass

• An extended flank or subcostal incision is reserved for unilateral fibrodysplastic lesions.

• The supracoeliac aorta may be selected as an in-flow source for the unilateral aortorenal by-pass.

• With the ipsilateral flank elevated, the incision is extended from the opposite semi-lunar line into the flank, between the costal margin and iliac crest.

• A left or right visceral mobilization allows access to the renal vasculature and the aortic crus.

• If necessary, the crus can be divided, and an extrapleural dissection of the descending thoracic aorta can provide access to the lower thoracic aorta for proximal control and anastomosis.

• Exposure of the distal portion of the right renal artery is achieved by colonic and duodenal mobilization.

• Mobilization of the left renal vein by ligation and division of the adrenal, gonadal and lumbar veins allows exposure of the entire left renal artery to the hilum.

• The autologous saphenous vein is used as a graft.

• When an end-to-side renal artery by-pass is performed, the anastomosis between the renal artery and the graft is performed first with a 6-0 or 7-0 monofilament polypropylene continuous suture (Fig. 2.4.1).

• Following this, the aortic anastomosis is performed, removing an ellipse of the anterolateral aortic wall. Sometimes an end-to-end anastomosis between the graft and the renal artery provides a better reconstruction.

• If the vein is small or sclerotic, a synthetic prosthesis preferable. A 6-mm thin-walled PTFE graft is quite satisfactory when the distal renal artery is of large calibre (> 4 mm).

Possible Complications of the Surgical Procedure

• Haemorrhage and/or thrombosis of the graft are the main complications of aortorenal by-pass, as is transient or permanent worsening of renal function [5].

Procedure 2

Dilatation of the Internal Carotid Artery

• The carotid bifurcation is dissected through a longitudinal incision in the neck along the anterior border of the sternocleidomastoid muscle.

• A graduated dilatation of the internal carotid artery is performed through a small arteriotomy, using arterial dilators.

Possible Complications of the Procedure

• Haemorrhage through perforation of the carotid artery is possible, and also thrombosis of the artery and cerebrovascular episode (stroke). Special Remarks

As is the case with most rare diseases, it is difficult to conduct a prospective study of various treatment options for fibromuscular dysplasia. Therefore, most treatment decisions are based on data derived from retrospective case and anecdotal reports.

Thanks to advances in imaging methods and enhancement of the interventional armamentarium, treatment has become less invasive and is now at least as effective as previous surgical approaches, while being associated with lower morbidity. Further study of the pathogenesis of fibromuscular dysplasia is needed in order to gain a better understanding of this disease.


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