Mesenteric Arterial Disease



Mesenteric Arterial Disease


Stefanos Giannopoulos

Ehrin J. Armstrong*


* Ehrin Armstrong, MD, is a consultant to Abbott Vascular, Boston Scientific, Cardiovascular Systems Incorporated (CSI), Medtronic, Philips, and PQ Bypass. All other authors have no relationship to disclose.



INTRODUCTION


Epidemiology

Mesenteric ischemia constitutes overall a rare entity that commonly presents among the elderly, and is attributed to reduced blood flow in the intestinal circulation that does not meet the metabolic demands of the corresponding viscera.1 Depending on the clinical scenario, mesenteric ischemia is divided into two types: acute and chronic mesenteric ischemia. The pathophysiologic mechanisms resulting in reduced blood flow include (1) mesenteric venous thrombosis; (2) arterial thrombosis; (3) nonocclusive mesenteric ischemia; and (4) arterial embolism.1,2 Independent of the underlying cause, both types (ie, acute mesenteric ischemia and acute on chronic mesenteric ischemia) of mesenteric ischemia eventually lead to intestinal wall necrosis, perforation, peritonitis, and death.2 The prevalence of acute mesenteric ischemia is estimated to be around 0.1% of all hospital admissions; however, the mortality associated with the disease rises to 80% in certain cases. Hence, early diagnosis and treatment are crucial to alter the disease’s course.3


Risk Factors

Atherosclerosis is one of the main causes of chronic mesenteric ischemia (almost 90% of cases), and therefore populations with a higher prevalence of comorbidities or conditions that are predisposed to advanced atherosclerosis (eg, smoking, hypertension, dyslipidemia, diabetes mellitus, metabolic syndrome, sedentary lifestyle) are at higher risk for chronic mesenteric ischemia. On the other hand, acute mesenteric ischemia has been attributed to embolic occlusion in 40% to 50% of cases, to arterial thrombosis of a stenosed mesenteric vessel in 20% to 35% of the cases, and to arteritis in almost 5% of the cases.1 Thus, several other factors that predispose to thrombus formation or embolization have been correlated with mesenteric ischemia as well, including but not limited to cardiac diseases (ie, arrhythmias, congestive heart failure, recent myocardial infarction, valvular disease), hypovolemia, and intra-abdominal tumor.1,2,4 Additionally, there has been observed an association between acute mesenteric ischemia incidence and increased age and female sex.5


PATHOGENESIS

Mesenteric ischemia is caused by an imbalance between intestinal blood supply and oxygen demand, which occurs either acutely or is a chronic process. Insufficient perfusion of the large and small intestines can be caused either from embolic/thrombotic arterial occlusion, venous thrombosis, or from nonocclusive entities, such as arterial vasospasm, hypovolemia, reduced effective blood flow (eg, congestive heart failure, states of low cardiac output), and reduced oxygen-carrying capacity from red blood cells (eg, anemia, methemoglobinemia, carboxyhemoglobinemia).1,2 Less frequently, dissection of the superior mesenteric artery is the trigger of acute mesenteric ischemia.6,7 The result of reduced arterial or venous blood flow is a hemorrhagic infarction and the severity of the disease depends on (1) the vessels affected; (2) the duration of occlusion/ischemia; (3) the overall hemodynamic status (ie, systemic blood pressure, volume status, blood flow); and (4) the collateral blood supply. Thus, damage to the intestinal vessel wall varies from reversible ischemia to permanent injury owing to transmural infarction, eventually causing bowel wall necrosis, perforation, and peritonitis.


CLINICAL PRESENTATION


Common Signs and Symptoms

Patients diagnosed with chronic mesenteric ischemia usually have a long-standing history of progressive, worsening epigastric postprandial pain (ie, 10-180 min after a meal), which leads to avoidance of eating and subsequent significant weight loss.8 Additionally, patients with chronic mesenteric ischemia often have history of vascular disease, including cerebrovascular accidents, coronary artery disease, and symptomatic peripheral artery disease.8 Nonspecific symptoms are gastrointestinal discomfort, experienced as nausea with/without vomiting and changes in bowel habits, such as diarrhea/constipation and flatulence.8,9,10

Patients with acute mesenteric ischemia present differently from those with chronic mesenteric ischemia, with the most important observation being the disproportionate pain that the patient experiences compared to physical examination findings. Traditionally, the pain associated with acute
mesenteric ischemia is described as diffuse, constant, difficult to localize, and moderate to severe in intensity. Related gastrointestinal symptoms that commonly present synchronously with the pain include nausea with/without vomiting in almost three quarters of acute mesenteric ischemia cases and abdominal discomfort/distension with/without diarrhea. As the bowel ischemia persists, intestinal bleeding, obstipation, and signs of sepsis may become more apparent. Among the different pathogenic mechanisms of acute mesenteric ischemia, acute arterial embolization is the most rapidly evolving and is associated with the most painful and robust presentation.

Patients presenting with acute mesenteric ischemia owing to intestinal arterial thrombosis usually have a history of chronic mesenteric ischemia with postprandial pain, whereas coronary artery disease and peripheral vascular disease are also commonly observed in this population. Thus, those patients usually develop acute mesenteric ischemia on a background of chronic mesenteric ischemia. However, due to the chronic course of the disease, collateral blood flow is better developed and, as such, the signs/symptoms at presentation are less severe than cases of arterial embolization. Similarly, patients with acute mesenteric ischemia attributed to nonocclusive arterial or venous disease (often elderly) usually develop symptoms of intestinal ischemia (eg, postprandial pain, acute abdominal pain, obstipation, intestinal bleeding) over several days and often these are preceded by a prodrome of intestinal irritation, discomfort, and/or malaise. The fourth type of acute mesenteric ischemia, caused by mesenteric venous thrombosis, usually affects the small intestine and is observed among younger patients with hypercoagulable states (eg, coagulopathies, malignancy, immobility, drug-induced hypercoagulability). It is characterized by insidious onset (over several days) and less severe abdominal pain compared to the other types of acute mesenteric ischemia.


Physical Examination Findings

The examination findings are relevant to the type of mesenteric ischemia, the different pathogenic mechanisms, and the progress of the disease at the time of presentation.1,2 Thus, the main findings of chronic mesenteric ischemia are signs of malnutrition, owing to the postprandial pain and fear of eating, whereas in some cases signs of peripheral vascular disease are apparent (eg, intermittent claudication, stable angina, decreased distal pulses).8,11 However, patients with chronic mesenteric ischemia may also present with acute on chronic mesenteric ischemia. The pathognomonic finding of acute mesenteric ischemia is that the patient complains of severe abdominal pain, although the abdominal examination is inconclusive. Nonetheless, if the disease has progressed (ie, intestinal wall infarction with necrosis and perforation), signs of peritonitis may be present. Moreover, in severe cases the patient may present with signs of sepsis and hemodynamic instability.1,2,11


Differential Diagnosis

Owing to the indolent course and nonspecific symptoms at onset, a high degree of clinical suspicion is required. Because most patients present with abdominal pain, all conditions that can cause abdominal pain should be considered in the differential diagnosis. See Table 83.1 for a list of differential diagnoses for abdominal pain. In addition, because of presenting signs of malnutrition, chronic mesenteric ischemia should be differentiated from malignancies and malabsorption syndromes.










May 8, 2022 | Posted by in CARDIOLOGY | Comments Off on Mesenteric Arterial Disease
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