Acute mesenteric ischemia: an emergency that requires a ...

Original article Anales de Radiolog?a M?xico 2015;14:66-88.

Acute mesenteric ischemia: an emergency that requires a comprehensive diagnostic approach.

Motta-Ram?rez GA1, S?nchez-Garc?a JC2, Ontiveros-Rodr?guez A3, L?pezRam?rez MA4, Rebollo-Hurtado V5, Garc?a-Ruiz A6, Noyola-Villalobos H7

Abstract

BACKGROUND: Acute mesenteric ischemia is a vascular emergency with mortality over 60%, which requires timely treatment. However, due to its heterogeneous pathophysiology and differences in degree and extent of ischemic damage, the clinical and radiological manifestations are varied and often nonspecific; consequently, a thorough analysis of medical background, laboratory studies, and clinical and radiological findings is recommended in order to establish a timely diagnosis.

OBJECTIVE: Identify the most common findings, direct and indirect, by computed tomography and determine low, intermediate, and high probability of a patient suffering from acute mesenteric ischemia on the basis of risk factors and clinical, biochemical, and radiological findings.

MATERIAL AND METHODS: We performed a retrospective, observational, cross-sectional study, with analysis of findings from computed tomography images of a series of cases of patients with diagnosis of acute mesenteric ischemia in a period of 9 years, 3 months and literature review. The purpose was to analyze the risk factors and clinical and biochemical data most commonly associated with acute mesenteric ischemia.

RESULTS: Our universe included tomographic studies of 27 cases of acute mesenteric ischemia, with average age of 60.8 years. The most common clinical finding was acute abdominal pain syndrome in 19 patients (70%); the most commonly associated history was type 2 diabetes mellitus and systemic high blood pressure in 7 (26%) patients each; 13 patients (48%), according to the clinical file, had laboratory studies, of whom 11 (85%) had leukocyte values of 9,200 to 68,000; the most commonly identified findings were: arterial filling defect 48%, intestinal pneumatosis 29%, venous filling defect 22%, bowel obstruction syndrome 22%, and identification of free fluid 22%.

CONCLUSION: It is advisable to conduct a quantitative analysis giving a specific value to the different findings, including risk factors, physical examination, laboratory studies, and image findings, to determine the risk of acute mesenteric ischemia in a patient with acute abdominal pain syndrome. CTA is the study with the greatest diagnostic precision.

KEYWORDS: mesenteric vascular occlusion; superior mesenteric artery; emission computed tomography

1 Radiologist. Postgraduate course on Sectional Imaging of the Body, from the Ionizing Radiation Department, CAT scan subsection. 2 Medical doctor, 3rd. year Resident of the Specialty Course and Residency in Radiology and Imaging. Escuela Militar de Graduados de Sanidad. 3 Medical doctor, 3rd year Resident of the Specialty Course and Residency in General Surgery. Escuela Militar de Graduados de Sanidad. 4 Medical doctor 4th year Resident of the Specialty Course and Residency in General Surgery. Escuela Militar de Graduados de Sanidad. 5 Radiologist. Postgraduate course on Sectional Imaging of the Body, staff doctor from the Ionizing Radiation Department, Head of the CAT scan subsection. 6 Medical doctor. Postgraduate course on Advanced Laparoscopic Surgery, staff doctor of the General Surgery Department. 7 Medical doctor. Postgraduate course on Advanced Transplant surgery, Head of the General Surgery Department. Hospital Central Militar, Blvd. Manuel ?vila Camacho s/n Lomas de Sotelo, Miguel Hidalgo, 11200 M?xico, D. F. 55573100, extensiones 1406 y 1928.

Received: Janueary 8, 2015

Accepted: January 20, 2015

Correspondence Gaspar Alberto Motta-Ram?rez radbody2013@.mx

This paper must be quoted as Motta-Ram?rez GA, S?nchez-Garc?a JC, OntiverosRodr?guez A, L?pez-Ram?rez MA, Rebollo-Hurtado V, Garc?a-Ruiz A et al. Isquemia mesent?rica aguda: urgencia que exige un abordaje diagn?stico integral. Anales de Radiolog?a M?xico 2015;14:66-88.

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Motta-Ram?rez GA et al. Acute mesenteric ischemia

INTRODUCTION

Acute mesenteric ischemia is not an isolated clinical entity but rather involves a complex group of abnormalities that include mesenteric artery embolic thrombosis, mesenteric venous thrombosis and non occlusive mesenteric ischemia.1 Table 12 and Figures 1-2.

Acute mesenteric ischemia is a disease that mainly involves patients over 60 years of age, with a male gender predominance occurring in 1 of every 1 000 hospital admissions; some series report up to 5% hospital mortality.3 Among the multiple factors that account for an increased incidence we find a more frequent diagnosis due to the growing elderly adult population as well as an increase in the number of patients in critical condition. In spite of advances of knowledge in pathophysiology, laboratory diagnosis and imaging studies, acute mesenteric ischemia is a potentially

lethal vascular emergency, associated to a mortality over 60% 1,4-6 if diagnosis takes more than 12 hours, and over 90% if it takes longer than 24 hours;7 its diagnostic approach is a clinical challenge.8

The challenge is to establish a timely and reliable diagnosis, in order to have a rapid intervention allowing to re-establish the mesenteric blood flow, thus preventing intestinal necrosis. Due to the heterogeneity in its pathophysiology and to the differences in grade and extension of ischemic damage, the clinical and radiological manifestations are diverse and often nonspecific. The key to an efficient management of this syndrome follows three principles: 1) high clinical suspicion; 2) proper selection of available imaging techniques to establish the diagnosis: 3) knowledge of factors that increase surgical efficacy when indicated. This approach must prevail to have a better outcome in caring for this disease. 3

Table 1. Three causes of acute mesenteric ischemia

Types of mesenteric ischemia

Acute mesenteric arterial embolism

Disease

Atrial fibrillation, myocardial infarction, valvular disease,

left ventricular aneurysm

Acute mesenteric arterial thrombosis

Atherosclerotic disease, trauma, infection

Clinical findings Early

Sudden onset of abdominal pain, irrelevant physical findings

Gradual postprandial pain, nausea, intestinal changes, irrelevant physical findings

Mesenteric venous thrombosis

Hypercoagulable state, closed trauma, infection, portal hypertension, pancreatisis, malignant focal

liver lesion

Subacute onset of abdominal pain, irrelevant physical

findings

Late

Increased abdominal pain, distention, absent bowel sounds, disturbances in mental status,

peritoneal signs, sepsis

Diagnostic test

Angiogram

Treatment

All sorts of hemodynamic support, correction of acidosis, antibiotics, gastric decompression

Superior mesenteric embolectomy, chronic anticoagu-

lation

Surgical revascularization

Anticoagulant treatment (heparin)

Intestinal infarction

Surgery

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The atheroma plaques are typically found in the first 2.5 from the origin of the superior mesenteric artery

Inferior pancreaticoduodenal artery

Middle colic artery

Right colic artery Emboli almost always lodge in sites of major branches

Ileocolic artery

Jejunal branches

Straight vessels

Figure 1. Vascular anatomy of acute mesenteric ischemia. Modified from reference 36.

Pathophysiology

Acute mesenteric ischemia involves an inadequate condition of tissue perfusion that prevents from meeting the metabolic demands from one or more of the organs included in the mesenteric circulation. It is estimated that the main cause of acute mesenteric ischemia is arterial occlusion with a thrombus in approximately 50% of cases.1,6,8,9 Most of the thrombi originate in the atrium or left ventricle from detachment of a mural thrombus or from valvular lesions. These thrombi are often associated with cardiac arrhythmias such as atrial fibrillation or hypokinetic regions resulting from a previous infarction. Around 15% of embolisms lodge in the origin of the superior mesenteric artery (Figures 1 and 2, Table 210) while the rest can lodge 3 to 10 cm distal to the origin of the middle colic artery. In up to 20% of cases the embolism that originates in the superior mesenteric artery is associated with concurrent emboli in some other vascular bed.10,11 Modified Table 2.10 It is important to consider that intestinal ischemia due to an embolism can be found with reactive mesenteric vasoconstriction reducing the collateral flow with exacerbation of the ischemic damage.

Risk factors

The risk factors that most often have been associated, in different case series, with this disease are atherosclerosis (90%), heart disease (85%), systemic hypertension (85%), atrial fibrillation (75%), smoking (50%), digitalis use (50%) and obesity (40%).1,2,6,9

Clinical presentation

Figure 2. Pathophysiology of acute mesenteric ischemia. Modified from reference 30.

Acute mesenteric ischemia involves a complex group of abnormalities that include mesenteric arterial embolic thrombosis, mesenteric venous thrombosis and non-occlusive mesenteric ischemia.1 The clinical picture is nonspecific.

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Motta-Ram?rez GA et al. Acute mesenteric ischemia

Tables 1 and 312 and Figures 1 and 2. Some authors have called it "acute mesentery artery syndrome"13 and in our hospital the term mesenteric stroke is used, which we try to include and recognize as acute mesenteric ischemia in the current paper, referring to the symptoms that most frequently are associated to this disease:

1. In the initial phase, hyperperistalsis, characterized by rapid intestinal transit, with severe abdominal pain syndrome and no clinical correlation with other abdominal diseases, diffuse, and location can be related to the ischemic site; for example, if it is found in the anterior bowel: periumbilical; middle bowel:

Table 2. Bowel regions, irrigation and collateral connections

Region

Irrigation

Collateral connections

Anterior bowel

Distal esophagus to the ampulla of Celiac artery Vater

Pancreatoduodenal arteries and distally the arc of Buhler

Middle bowel

Duodenal region of the ampulla of Superior mesenteric Pancreatoduodenal arteries and proximally the arc of Buhler,

Vater to the splenic flexure of colon artery

marginal artery of Drummond and the arc of Riolan

Posterior bowel

Splenic flexure to the distal portion of Inferior mesenteric Marginal artery of Drummond and the proximal arc of Riolan.

the sigmoid colon

artery

Distally, superior and middle hemorrhoidal arteries

Cloacal origin

Branches of the infe- Proximally the superior and middle hemorrhoidal arteries rior hypogastric artery

Table 3. Clinical features and CT findings in mesenteric ischemia

Features Incidence Onset Risk factors

Arterial occlusion

Venous occlusion

Non occlusive

60-70% of AMI

5-10% of AMI

20% AMI

Acute

Subacute

Acute or subacute

Arrythmia, myocardial infarc- Portal hypertension, venous Hipovolemia, low heart out-

tion, valvular disase, athero- hypercoagulopathy, right heart put, digoxin, hypotension,

sclerosis, prolonged hyper- failure

alpha adrenergic agonists

tension

Abdominal wall

Thin, unchanged or thickened Thickened with reperfusion

Unchanged or thickened with perfusion

Attenuation of the abdominal Not characteristic wall in simple phase

Low with edema; high with Not characteristic bleeding

Enhancement of the abdomi- Reduced, absent, in target or Reduced, absent, in target or Reduced, absent, with heter-

nal wall in contrast phase high with reperfusion

increased

ogenous distribution

Intestinal dilatation Mesenteric vessels

Mesentery

Not evident

Moderate to prominent

Not evident

Defect or defects in arteries, Defect or defects in veins, No defects, arterial constric-

arterial occlusion, SMA diam- congestive veins

tion

eter > SMV

Homogenous until an infarc- Heterogenous with ascites tion occurs

Homogenous until an infarction occurs

SMA: superior mesenteric artery; AMI: acute mesenteric ischemia; SMV: superior mesenteric vein.

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infraumbilical; posterior bowel: pelvic; pain does not increase with palpation and is not associated with abdominal stiffness. It is accompanied by nausea, vomiting (75% and abdominal distention (25%).8,13-16

2. All this makes an early diagnosis of this condition difficult because of the similarity to other intra-abdominal processes.

Laboratory tests

They can be useful in the diagnosis of acute mesenteric ischemia, but only in its late stage. Total leukocyte count above 20 000 may be useful, with 80% sensitivity and 50% specificity, metabolic acidosis (38% sensitivity, 84% specificity) and high D dimer (40% sensitivity, 89% specificity).5 It has also been shown that low lactate concentrations can help to rule out the possibility of acute mesenteric ischemia and avoid unnecessary laparotomies, especially in elderly patients. Enzymes such as creatinine kinase, lactate dehydrogenase (LDH) and alkaline phosphatase may be useful in the diagnosis of a transmural infarction, but they have low sensitivity in early stages of acute mesenteric ischemia.2,5 In current times, the role of laboratory markers in acute mesenteric ischemia is limited.5 Table 3.12 Lactate dehydrogenase has been said to be a marker that suggests acute mesenteric ischemia;17 it originates from bacteria such as Escherichia coli in the intestinal luman. The hypothesis is that concentrations are increased during acute mesenteric ischemia due to bacterial translocation and bacterial overgrowth after a lesion in the intestinal mucosa. However, in a recent review, sensitivity and specificity of lactate dehydrogenase proved to be only 0.82 y 0.48, respectively.17 Table 4.18

Imaging studies

A simple X-ray can be normal in up to 25% of cases5-7 with nonspecific findings in 50% and,

in the remaining 25%, it is feasible to identify, 12 hours after the initiation of acute mesenteric ischemia, mural digital impressions resulting from edema or bleeding, pneumatosis, pneumobilia and gas in the portal vein. Evaluation with positive oral contrast agent (barium) is contraindicated.1,2,5,9

Ultrasound plays a limited role in the evaluation of acute mesenteric ischemia due to the fact that an important number of patients have air distention and dilated bowel loops making this imaging method technically difficult or impossible. It can be more useful in the on invasive evaluation can be more useful in patients with symptoms of chronic acute mesenteric ischemia.19 Doppler ultrasound can show the stenotic area, the occlusions in the celiac trunk or in the superior mesenteric artery with 92-100% sensitivity and 70-89% specificity. Doppler ultrasound is not a recommended study in patients with high suspicion of acute mesenteric ischemia.14,15

CT scan with intravenous contrast, called CT angiography (CTA), facilitates the diagnosis of primary acute mesenteric ischemia with 83.3% sensitivity and 95.5% specificity.1,4,5 It is considered to be the method of choice to reach1,5,7-9 this diagnosis:1 it is a non invasive study, with 100% positive predictive value and a negative predictive value of 94%.14,20 Figure 3.11 Images are obtained from the lung base to the symphysis pubis with a collimation of 0.5 a 2.5 mm and a 1.0-2.0 pitch. For reconstruction, images should have sections of 0.7 mm thickness. The thinnest 1-2 mm sections, in arterial phase, will be used in the multiplanar reconstructions to evaluate the origin of the mesenteric arteries and their variants. For the arterial phase, 100-150mL of IV non ionic contrast at a rate of 2-3.5 mL/s, scanning is started with 30 and 60 second delays. 21-23 The study must be multiphasic, since it is necessary to recognize indirect findings starting from the simple phase, such as vascular calcification sites, increased vascular density from clotting and in-

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