Diagnosis and management of fibromuscular dysplasia and segmental arterial mediolysis in gastroenterology field: A mini-review

The vascular diseases including aneurysm, occlusion, and thromboses in the mesenteric lesions could cause severe symptoms and appropriate diagnosis and treatment are essential for managing patients. With the development and improvement of imaging modalities, diagnostic frequency of these vascular diseases in abdominal lesions is increasing even with the small changes in the vasculatures. Among various vascular diseases, fibromuscular dysplasia(FMD) and segmental arterial mediolysis(SAM) are noninflammatory, nonatherosclerotic arterial diseases which need to be diagnosed urgently because these diseases could affect various organs and be lethal if the appropriate management is not provided. However, because FMD and SAM are rare, the cause, prevalence, clinical characteristics including the symptoms, findings in the imaging studies, pathological findings, management, and prognoses have not been systematically summarized. Therefore, there have been neither standard diagnostic criteria nor therapeutic methodologies established, to date. To systematically summarize the information and to compare these disease entities, we have summarized the characteristics of FMD and SAM in the gastroenterological regions by reviewing the cases reported thus far. The information summarized will be helpful for physicians treating these patients in an emergency care unit and for the differential diagnosis of other diseases showing severe abdominal pain.

Pancreatectomy and splenectomy for a splenic aneurysm associated with segmental arterial mediolysis

Segmental arterial mediolysis(SAM) is characterized by intra-abdominal, retroperitoneal bleeding or bowel ischemia, and the etiology is unknown. A 44-year-old man complaining of abdominal pain was admitted to our hospital. He had been admitted for a left renal infarction three days earlier and had a past medical history of cerebral aneurysm with spontaneous remission. The ruptured site of the splenic arterial aneurysm was clear via a celiac angiography, and we treated it using trans-arterial embolization. Unfortunately, the aneurysm reruptured after two weeks, and we successfully treated it with distal pancreatomy and splenectomy. We recommended a close follow-up and prompt radiological or surgical intervention because SAM can enlarge rapidly and rupture.

Segmental arterial mediolysis: A clinical-pathologic review, its role in fibromuscular dysplasia and description and differential diagnosis of the masquerader-muscular artery cystic necrosis

Segmental arterial mediolysis (SAM) is an uncommon non-inflammatory iatrogenic arteriopathy caused by alpha-1 adrenergic agonists or Beta-2 agonists able to release norepinephrine from the peripheral nervous system. Causative agents include adrenergic agonists used to control blood pressure, B-2 tocolytic agonists, and ractopamine used as a repartitioning agent in animal husbandry. The liberated norepinephrine both injures and stimulates a robust reparative response in the muscular arteries in the abdomen, brain base, and coronary arteries. This response may be augmented by endothelin-1 formed in the arterial adventitia. Three types of arterial lesions develop in the injurious stage: 1) apoptotic induced mediolysis, 2) separation of the outer media from the adventitia and 3) the formation of arterial gaps. The latter enlarge, particularly in elderly patients, to form gap-aneurysms complicated by dissections and dissecting an- eurysms that when ruptured cause the calamitous hemorrhages that clinically announce SAM. The other types of injury remain clinically silent but with repair develop sequelae and can metamorphose into fibromuscular dysplasia. The sequelae are mainly asymptomatic but may cause arterial stenosis and ischemic lesions. The definitive diagnosis of SAM re- quires histological conformation but misinterpreta- tion of smooth muscle vacuolar change has caused di- agnostic errors. Muscular artery cystic necrosis a newly named non-inflammatory muscular artery ar- teriopathy may be confused with SAM both clinically and pathologically. This arteriopathy represents the muscular artery equivalent of cystic media necrosis of the elastic arteries since it exhibits similar morphol- ogic features and can occur concomitantly with this entity. Adrenergic agents to counter hemorrhagic shock in SAM are contraindicated since they may intensify injury and create new lesions. The use of norepinehrine antagonists introduces a new, but as yet untested, treatment option for SAM.

Segmental arterial mediolysis, reparative phase: An analysis and case report showing conversion to fibromuscular dysplasia with renal infarction

Segmental arterial mediolysis (SAM), an uncommon arteriopathy putatively caused by norepinephrine released by alpha-1 adrenergic agonists or some Beta-2 agonists capable of releasing norepinephrine from the peripheral sympathetic nervous system potentially can present ischemic and organ injury symptoms caused by sequelae created in its reparative phase in lieu of catastrophic hemorrhages announced in its injurious phase. The case documents this presentation—the patient presenting renal infarcts and ischemic lesions causing abdominal angina, hypertension and a nephrectomy event developing 10 years after prolonged ritodrine treatment for premature labor. This agent may have directly caused SAM or sensitized the patient to agonists causing SAM encountered at a latter date. A variety of lesions derived from injurious phase arterial injuries characterize reparative phase SAM. All were encountered in a hilar branch of the resected renal artery. These included side-by-side sequela aneurysms grossly forming a large fusiform aneurysm, granulation tissue filling adventitial medial tear spaces in which a dissecting hematomas developed, medial muscle loss centered to the outer media repaired with fibrous tissue, arterial stenosis created by reparative intimal plaques, and arterial thrombo-embolism. These lesions were mirrored in accompanying radiologic studies. The accompanying renal vein exhibited changes consistent with repair of the spastic venous angiopathy that often accompanies abdominal SAM. This angiopathy, putatively induced by Endothelin-1, suggested that this agent played a role in the genesis of the arterial lesions. Angiographic resolution of non-treated sequelae occurred in 5 months either spontaneously or due to treatment with bosentem. Conclusions: The histologic and angiographic changes demonstrate that the clinical onset of reparative SAM may be significantly delayed to produce ischemic lesions, renal infarction and in this case report, medial fibromuscular dysplasia in the hilar branch of the renal artery.

A diagnostic dilemma:acute abdomen presenting as segmental arterial mediolysis masked by a ruptured hepatocellular carcinoma

A 65-year-old male was brought to our hospital with right upper abdominal fullness sensation and recent body weight loss of about 3 kg.The patient had developed episodes of melena following progressive abdominal muscular guarding and drop of haemoglobin level to 6.3 g/dL.An abdominal computed tomography scan disclosed a ruptured hepatocellular cell carcinoma.A segmental arterial mediolysis was found on the superior mesenteric artery in the process of repairing the ruptured right hepatic artery with the assistance of angiography.Transarterial embolization was carried out and permanent haemostasis was achieved.

Ruptured gastric artery aneurysm:An uncommon manifestation of microscopic polyangiitis

Gastric artery aneurysm is a rare and lethal condition,and is caused by inflammatory or degenerative vasculopathies.We describe herein the clinical course of a patient with a ruptured gastric artery aneurysm associated with microscopic polyangiitis.Absence of vasculitic changes in the aneurysm resected and negative results of autoantibodies interfered with our diagnostic process.We should have adopted an interventional radiology and initiated steroid therapy promptly to rescue the patient.