Update In Management Of Mesenteric Ischemia

Abstract

Mesenteric ischemia occurs when perfusion of the visceralorgans fails to meet normal metabolic requirements. Thisdisorder is categorized as either acute or chronic on the basisof the duration of symptoms. AMI occurs rapidly during hours to days and frequentlyleads to acute intestinal infarction requiring resection. The most common causes are embolization tothe mesenteric arteries and acute thrombosis related to apreexisting plaque. CMI is amore insidious process and progresses during weeks to severalmonths. The most common cause is progressiveocclusive disease of the visceral arteries. Atherosclerosis is the most common cause of CMI, andpatients frequently have a history of smoking, hypertension and hyperlipidemia. Impaired intestinal perfusion in the absence of thromboembolicocclusion is termed nonocclusive mesenteric ischemiaand makes up approximately 5% to 15% of cases. It commonly occurs secondary to cardiac disease, particularlysevere congestive heart failure, and in patients who haveundergone cardiac surgery. MVT constitutes 5% to 15% of all cases of mesentericischemia. Involvement is usually limited to the superiormesenteric vein, but the inferior mesenteric, splenic, andportal veins can also be involved. Presentation of AMI is more dramatic and severe, oftenwith rapid clinical deterioration. Nausea, vomiting, diarrhea,emptying symptoms, and distention can also occur. Classically,the pain is out of proportion to the findings on physicalexamination. Patients with NOMI or MVT typically present with aslower, more insidious clinical course. Frequently, patientswith NOMI are critically ill, hospitalized, intubated patientswho experience a sudden deterioration in their clinical condition. Postprandial abdominal pain and progressive weight loss arethe most common symptoms in patients with CMI. Pain isoften described as dull and crampy and located in the midepigastricregion. Doppler ultrasound is a useful tool for the early, noninvasive diagnosis ofvisceral ischemic syndromes. The intestinal wall can also beassessed with a high degree of accuracy by high-resolution transabdominal ultrasound. Computed tomography is an accurate, noninvasiveimaging modality for diagnosis of mesenteric ischemia. Although MRA takes significantly longer to perform thanCTA, it avoids the radiation exposure associated with CTA.Patients with hypersensitivity to iodinated contrast agentsmay also benefit from MRA. Standard workup includes DUS toscreen those thought to have CMI. CTA is used routinelybefore intervention for AMI, CMI, and MVT. The goal of therapy for patients with mesenteric ischemia isthe prompt restoration of blood flow to the visceral organs. Medical treatment alone is not effective in patients withsymptomatic mesenteric ischemia Before operation, aggressive fluid resuscitation with restorationof adequate urine output is required owing to thefrequent finding of severe dehydration on presentation. Electrolyteabnormalities and metabolic acidosis should also becorrected Broad-spectrum intravenous antibiotics withaggressive fluid resuscitation can lead to decreased mortality. Laparotomy with visceral revascularization can be used totreat patients with both AMI and CMI. Patients presentingwith signs and symptoms of AMI require urgent abdominalexploration, assessment of bowel viability, and revascularization. After vascular reconstruction and reperfusion, the bowelshould be reassessed. Most patients should undergo “second-look” laparotomyin 24 hours to reassess bowel viability and the needfor further resection. The majority of open mesentericrevascularizations consist of bypass with a bifurcatedsynthetic graft from the supraceliac aorta to the celiac arteryand SMA. Advances in endovascular techniques have greatly expandedthe role of percutaneous interventions for patients with mesentericischemia in recent years. Balloon angioplasty withstenting has surpassed open surgery as the dominant methodof revascularization for CMI, and an endovascular approachis now generally accepted as primary therapy. In contrast,the adoption of endovascular modalities for treating AMI hasbeen slower. This is likely because mostpatients with AMI have some degree of bowel ischemiaand many require laparotomy for adequate evaluation andpotential resection.