Introduction
Mesenteric ischemia. CT scan in a 72-year-old man with bright-red blood per rectum and abdominal pain shows thickening of the ascending colon and hepatic flexure. The differential diagnoses included conditions with an infectious etiology versus ischemia. Magnetic resonance angiography was performed, and images showed stenosis at the origin of the superior mesenteric artery.
Mesenteric ischemia. CT scan in an 83-year-old woman obtained after suggestive sonographic findings of portal venous air were observed confirms the presence of air in the portal-venous system and proximal small bowel mucosal edema. These findings suggest ischemia of the affected bowel.
Background
Mesenteric ischemia is characterized by inadequate blood flow to or from the involved mesenteric vessels supplying a particular segment of bowel. The organs typically affected are the small bowel or colon. The source of blood that is lacking can be arterial or venous, and hemodynamically, the cause can be occlusive or nonocclusive. Mesenteric ischemia can be acute or chronic.1
The diagnosis of mesenteric ischemia often is a challenge to both clinicians and radiologists. Patients with inflammatory bowel disease and infectious colitis can present with similar physical signs and symptoms, including cramping abdominal pain, diarrhea, leukocytosis, and hematochezia. Bowel wall thickening is a finding common to all 3 types of disease; however, the pattern of vascular distribution can sometimes narrow the differential diagnosis.
Related eMedicine topics:
Chronic Mesenteric Ischemia
Acute Mesenteric Ischemia
Mesenteric Ischemia (from Emergency Medicine)
Presentation
Demographics
- Mesenteric ischemia can have many causes and presents with a wide variety of clinical and radiologic findings. Arterial sources far outnumber venous sources by a ratio of approximately 9 to 1. Similarly, arterial occlusive disease occurs more frequently than nonocclusive disease by a ratio of approximately 9 to 1.
- The major cause of mortality in patients with mesenteric ischemia is bowel necrosis. Mortality from all causes is as high as 70%. However, several factors (particularly, the adequacy of collateral vessels) account for variability in mortality rates in different patient populations.
- Most patients who develop mesenteric ischemia are older than 50 years. Venous causes tend to affect a wider range of patients.
Presentation and natural history
The etiologies of mesenteric ischemia are many. Arterial causes account for most cases and include atheromatous plaque formations with the development of intimal calcifications, embolic phenomena from cardiac disease, abdominal aortic aneurysms with dissection into the superior mesenteric artery (SMA), and hypoperfusion secondary to hypovolemic shock or low-flow cardiac failure. Chronic arterial disease results from atherosclerosis, fibromuscular dysplasia, and vasculitis. Both occlusive and nonocclusive subtypes can occur; however, occlusive disease is more frequent than nonocclusive disease in the acute setting. The SMA and the inferior mesenteric artery (IMA), including corresponding smaller colic and intestinal branches, typically are involved more frequently than the celiac artery.
Venous causes of mesenteric ischemia are encountered less frequently. In these cases, bowel ischemia results from decreased mesenteric outflow of deoxygenated blood rather than from decreased perfusion of oxygen-rich blood. The particular cause of venous ischemia in a patient often is not clear. Predisposing risk factors are associated with thrombosis and include recent abdominal surgery, infection, and hypercoagulable states. Mortality rates in this subset of patients generally are low. The superior mesenteric vein (SMV) is involved more often than the inferior mesenteric vein (IMV).
Additional rare causes of mesenteric ischemia include small bowel herniation, adhesions, intussusception, and, rarely, antiphospholipid antibody syndrome (APS). APS is associated with hypercoagulable states secondary to circulating immunoglobulins that interact with phospholipids in cell membranes. The 2 known circulating immunoglobulin antibodies are anticardiolipin antibody and lupus anticoagulant antibody. These 2 entities have been linked to deep venous thrombosis, cerebrovascular accidents, and recurrent spontaneous abortions. APS also has been shown to be associated with abdominal vascular thrombosis and ischemia. In a recent study by Kaushik et al, 13 (31%) of 42 patients with APS had CT findings of bowel ischemia.2
Large or smaller segments of bowel may be involved, depending on the location of the occlusion. The underlying mechanisms of injury are identical whether the source is complete occlusion or hypoperfusion. With diminishing blood flow, the susceptible bowel mucosal layer becomes anoxic, leading to cell fragility and irreversible cell death. Eventually, the mucosa becomes edematous and inflamed and begins to slough and ulcerate. Then, the patient experiences malabsorption, which causes diarrhea and rectal bleeding. If collateral circulation is adequate, perfusion may be restored with resultant fibrosis.
The evaluation of patients who present to the emergency department with an acute abdomen is often a challenge. Symptoms are usually nonspecific and may be confused with other causes of abdominal pain, including diverticulitis, appendicitis, Crohn disease, peptic ulcer disease, and pelvic inflammatory disease. Classic acute mesenteric ischemia presents with acute abdominal pain that initially is characterized as cramping pain, followed by a continuous dull pain.Unlike diverticulitis and appendicitis, in which the pain is typically in the lower quadrants, the pain in mesenteric ischemia is usually more diffuse. However, depending on the particular segment involved, the pain may be more localized to one side of the abdomen. Ischemic pain that involves the SMA tends to be more diffuse because both the small bowel and the right colon may be involved, corresponding to the vascular territory. Ischemic pain toward the left side more often involves the distribution of the IMA. However, if only small contributing arterial branches are involved, such as the right colic branch, the pain may be located on the right.
As ischemia progresses, mucosal sloughing and necrosis ensue. Bloody diarrhea, gross bleeding per rectum, and/or leukocytosis are delayed manifestations. In addition, diagnostic symptoms may be further confused if peritoneal signs resulting from bowel infarction and necrosis are noted.
Patients with chronic mesenteric ischemic disease present with postprandial abdominal pain, typically within several minutes of a meal. These patients typically are aware of the precipitating events that lead to the symptoms and, thus, are reluctant to eat, as with patients who have peptic ulcer disease. Symptoms correspond to the chronicity of disease and include weight loss and chronic diarrhea from malabsorption.
Treatment
- The treatment of acute occlusive mesenteric ischemia is usually surgical resection of the infarcted bowel segment.
- Chronic mesenteric ischemia resulting from poor collateral circulation is not a surgical emergency and may be treated conservatively.
- Nonocclusive mesenteric ischemia usually is treated nonsurgically.
- Depending on the cause, direct arterial vasodilatation can be used to improve bowel perfusion.
Preferred Examination
Pertinent history and a physical examination can narrow the differential diagnosis in patients with an acute abdomen, particularly when considering the timing of the event, localizing signs and symptoms, and vascular distribution of the pain.
Unless the patient is unstable, imaging is the criterion standard for diagnosis.
- Upright and supine plain abdominal radiographs typically should be requested first to evaluate for free air, obstruction, ileus, intussusception, or volvulus.
- Eventually, a computed tomography (CT) scan using oral and, preferably, intravenous contrast material may be needed if the cause is not apparent on plain radiographs.
- Sonography, barium enema study, and angiography are typically reserved for inpatient use after the patient is admitted from the emergency department, depending on the availability of resources and the findings on the CT scans.
Limitations of Techniques
- Plain abdominal radiographs are helpful initial screening tools for excluding certain manifestations of disease. Although findings in plain radiographs may be sensitive, they are typically nonspecific. For instance, the presence of mucosal edema, small-bowel dilatation, and free air on plain radiographs are sensitive findings; however, these findings are not useful in localizing or determining the etiology of the event.
- CT scans are more specific regarding the cause of the findings, and CT scans may occasionally reveal additional findings, such as the presence of portal venous gas, which may be missed on plain radiographs.
- Nonenhanced CT scans have an inherent limitation. CT scans obtained without oral contrast enhancement are not helpful in differentiating mucosal thickening from nonopacified bowel loops.
- Although CT findings may help in localizing a diseased segment of bowel, differentiating a venous origin from an arterial origin in thrombosis often is difficult, even with the proper intravenous administration of contrast material.
- In addition, differentiating ischemic colitis from infectious colitis often can be difficult using CT scans.
Differential Diagnoses
| Appendicitis | Necrotizing Enterocolitis |
| Bowel, Trauma | Pneumatosis Intestinalis |
| Colitis, Pseudomembranous | Typhlitis |
| Colon, Adenocarcinoma | Ulcerative Colitis |
| Colon, Diverticulitis | |
| Crohn Disease |
More on Mesenteric Ischemia |
 Overview: Mesenteric Ischemia |
| Imaging: Mesenteric Ischemia |
| Follow-up: Mesenteric Ischemia |
| Multimedia: Mesenteric Ischemia |
| References |
| Next Page » |
References
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Kaushik S, Federle MP, Schur PH, et al. Abdominal thrombotic and ischemic manifestations of the antiphospholipid antibody syndrome: CT findings in 42 patients. Radiology. Mar 2001;218(3):768-71. [Medline].
Cademartiri F, Palumbo A, Maffei E, Martini C, Malagò R, Belgrano M, et al. Noninvasive evaluation of the celiac trunk and superior mesenteric artery with multislice CT in patients with chronic mesenteric ischaemia. Radiol Med. Oct 29 2008;[Medline].
Lee SS, Ha HK, Park SH, Choi EK, Kim AY, Kim JC, et al. Usefulness of computed tomography in differentiating transmural infarction from nontransmural ischemia of the small intestine in patients with acute mesenteric venous thrombosis. J Comput Assist Tomogr. Sep-Oct 2008;32(5):730-7. [Medline].
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Zalcman M, Sy M, Donckier V, et al. Helical CT signs in the diagnosis of intestinal ischemia in small-bowel obstruction. AJR Am J Roentgenol. Dec 2000;175(6):1601-7. [Medline].
Burkart DJ, Johnson CD, Ehman RL. Correlation of arterial and venous blood flow in the mesenteric system based on MR findings. 1993 ARRS Executive Council Award. AJR Am J Roentgenol. Dec 1993;161(6):1279-82. [Medline].
Baccoli A, Manconi AR, Sau P, Pisu S, Serra C, Sau M. [Duplex US evaluation of mesenteric vessels in acute abdomen. Perspective study on 325 patients]. G Chir. Oct 2008;29(10):449-54. [Medline].
Lim HK, Lee WJ, Kim SH, et al. Splanchnic arterial stenosis or occlusion: diagnosis at Doppler US. Radiology. May 1999;211(2):405-10. [Medline].
Roobottom CA, Dubbins PA. Significant disease of the celiac and superior mesenteric arteries in asymptomatic patients: predictive value of Doppler sonography. AJR Am J Roentgenol. Nov 1993;161(5):985-8. [Medline].
Further Reading
Keywords
mesenteric ischemia, bowel infarction, bowel ischemia, intestinal angina, ischemic colitis, bowel necrosis, bowel ischemia
