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Acute mesenteric ischemia (part I) – Incidence, etiologies, and how to improve early diagnosis

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Abstract

Acute mesenteric ischemia (AMI) is generally thought to be a rare disease, but in fact, it is more common cause of acute abdomen than appendicitis or ruptured abdominal aortic aneurysm in patients over 75 years of age. In occlusive AMI, surgical treatment without revascularization is associated with as high as 80% overall mortality. It has been shown that early diagnosis with contrast-enhanced computed tomography and revascularization can reduce the overall mortality in AMI by up to 50%. However, only a minority of patients with AMI are being treated actively with revascularization in the United States, and the situation is very likely similar in Europe as well. What can we do to improve diagnostic performance, so that more patients get proper treatment? The diagnosis is a collaborative effort of emergency department surgeons, gastrointestinal and vascular surgeons, and radiologists. The etiological categorization of AMI should be practical and guide the therapy. Furthermore, the limitations of the diagnostic examinations need to be understood with special emphasis on computed tomography findings on patients with slowly progressing “acute-on-chronic” mesenteric ischemia.

Introduction

In 1926, A.J. Cokkinis wrote “the diagnosis is impossible, the prognosis hopeless and the treatment useless” [1]. Ninety years later, it is still a common presumption that acute mesenteric ischemia (AMI) is a rare condition which inescapably leads to the death of the patient. The reason for such dreary reputation is not so much based on facts but because AMI is too often found too late when the treatment outcome is inevitably poor. In the early 1990s in Finland, two-thirds of patients with AMI were treated with mere surgical exploration or comfort care resulting in certain death. With good luck, in one-third of the cases, the patient could be treated with bowel resection yielding 50% survival. Open surgical revascularization was attempted in only 7% of the cases and the results were discouraging. The overall mortality of patients with AMI was more than 80% [2].

What has changed in the past two decades? The most important evolutionary step is that today, we have the ability to perform multi-slice contrast-enhanced computed tomography (CT), the most important diagnostic examination in AMI, to nearly all patients with acute abdominal pain at any given time. Second, our endovascular capabilities have taken a leap from the conventional time-consuming catheter-directed thrombolysis to mechanical thrombectomy using dedicated aspiration catheters, and to utilizing stents that are designed especially for visceral arteries. We have seen that with early diagnosis and treatment, more than half of patients with AMI can be rescued [3]. In the United States, endovascular treatment has become nearly as common therapeutic approach as open revascularization in AMI according to studies based on the Nationwide Inpatient Sample (NIS) by Schermerhorn, Lo, and colleagues [4], [5]. The in-hospital mortality of American patients undergoing open or endovascular repair for AMI declined from 51% in year 1995 to 26% in 2010 [5].

However, what does not seem to have changed, is that even today, according to NIS, the overall revascularization rate in AMI was no more than 6% in the year 2010 in the United States [5]. In another study, Beaulieu and co-workers found a total of 23744 hospital admissions for AMI registered in the NIS database from 2005 through 2009. At that time, only 3% received an attempt at open (n = 514) or endovascular (n = 165) revascularization, while 17% were treated with bowel resection alone, and an alarming rate of 80% received no intervention whatsoever [6]. There are no other large population based data of the revascularization rate in AMI, but we can only assume that not all patients in Europe, either, get timely diagnosis and proper treatment.

To overcome the diagnostic-related challenges in AMI, we must first acknowledge that AMI is not a rare entity but actually a quite common condition in elderly patients. Second, we must understand the complex pathophysiology and diverse clinical presentation of the disease. The CT signs at early stages of AMI are often subtle and difficult to detect, and therefore, the key to diagnosis is clinical suspicion. Third, the modern treatment of AMI requires a multidisciplinary team of gastrointestinal surgeons, vascular surgeons, and interventional radiologists. We need a practical etiological categorization of AMI that will guide the treatment and a simple algorithm for the various treatment options in different situations.

Section snippets

Incidence

Between 1970 and 1982 in Malmö (Sweden), autopsies were conducted on as many as 87% of the deceased in the population of approximately 250 000 inhabitants [7]. According to this data, the annual incidence of AMI, diagnosed at autopsy or operation, was 12 per 100 000 inhabitans. The distribution of etiology in AMI was roughly 2/3 thromboembolic occlusive mesenteric ischemia, 1/6 non-occlusive mesenteric ischemia (NOMI), and 1/6 mesenteric venous thrombosis (MVT). Thus, the most common cause of

The classical etiological categorization of AMI

Conventionally, AMI is stratified into four groups by etiology; arterial embolism, arterial thrombosis, venous thrombosis and NOMI [29]. Chronic atherosclerotic obstruction of the mesenteric arteries is traditionally associated with chronic mesenteric ischemia (CMI). This classical categorization has not evolved since the time when angiography was the gold standard diagnostic investigation and bowel resection was the main therapeutic option. Owing to modern CT technology, we now get more

Laboratory tests

Classically, patients with AMI have leukocytosis, metabolic acidosis, elevated d-dimer, and elevated serum lactate. The challenge is that the conventional laboratory tests are very unspecific at presentation such as leukocytosis or d-dimer. None of them can be used to rule in the possibility of AMI. d-dimer may be used as an exclusion test, where a negative test very likely excludes acute thromboembolic occlusion of the SMA at presentation [37], [38]. Arterial lactate is often negative in the

Characteristics of AMI in elderly patients

As shown in Fig. 1, the spectrum of differential diagnoses in acute abdomen is very different in the elderly than in the younger patients. The incidence of AMI is roughly 10-fold in 80-year-old people versus in 60-year-old population [8], [13]. The proportion of patients with atherosclerotic etiology of AMI is significantly higher in the elderly (Table 4). Based on the Kuopio cohort, embolic etiology of AMI was as common as mesenteric arterial occlusive disease in patients aged 75 years or

Prognosis

An active endovascular-first strategy in Kuopio with 76% revascularization rate resulted 42% overall mortality rate in patients with occlusive AMI [3]. In comparison to the previous 82% mortality for AMI in Finland, this is a significant improvement [2]. Even so, it has to be individually considered, when the aggressive treatment is futile and doomed to result in unnecessary suffering. Due to the old age and comorbidities in AMI patients, the long-term survival is poor regardless of the

Summary

AMI appears to be relatively common in elderly patients – more common than appendicitis in patients aged over 75 years (Table 1). This is important to acknowledge, because clinical suspicion is a major factor in the early diagnosis AMI and in the correct interpretation of CT findings. If AMI is suspected, contrast-enhanced CT should be performed without fear of contrast-induced nephropathy, preferably in arterial and venous phases. Clinicians should be aware that the clinical presentation of

Conflict of interest

None.

Acknowledgements

The authors would like to acknowledge Interventional Radiologist of Finland society and Rättimäki Cardiovascular Society for funding the writing of this review. The funders did not have any role in the making of this manuscript.

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