Demographics, Diagnosis, Management, and Outcomes of Non-occlusive Mesenteric Ischemia: a Substudy of a Prospective Multicenter Observational Study (AMESI)
Conditions: Non-Occlusive Mesenteric Ischemia
Sponsor: University of Tartu

 
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Demographics, diagnosis, management, and outcomes of non-occlusive mesenteric 
ischemia: a substudy of a prospective multicenter observational study (AMESI) 
 
Principal investigator 
Vladislav Mihnovitš, MD 
Tartu University Hospital, Department of Anesthesiology and Intensive care 
Estonia, Tartu City, Puusepa 8 
+37253715953 
vladislav.mihnovits@ut.ee  
 
Sub investigators 
Annika Reintam Blaser, MD, PhD 
Luzerner Kantonsspital, Switzerland 
Associate Professor of Anesthesiology and Intensive Care, University of Tartu, Department of 
Anesthesiology and Intensive Care 
Estonia, Tartu City, Puusepa 8 
+3725142281 
annika.reintam.blaser@ut.ee  
 
Kadri Tamme, MD, PhD 
Tartu University Hospital, Department of Anesthesiology and Intensive Care 
Estonia, Tartu City, Puusepa 8 
+3727318414 
kadri.tamme@kliinikum.ee  
 
Joel Starkopf, MD, PhD 
Tartu University Hospital, Department of Anesthesiology and Intensive Care 
Estonia, Tartu City, Puusepa 8 
+37253318400 
joel.starkopf@ut.ee  

 
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Merli Mändul 
Institute of Mathematics and Statistics, University of Tartu 
Estonia, Tartu City, Narva mnt 18 
merli.mandul@ut.ee  
 
Funding Sponsor 
Study is funded by Grant PRG 1255 (duration 2021-2025). 
Document date 
18.04.2025 
Summary 
Title: Demographics, diagnosis, management, and outcomes of non-occlusive mesenteric 
ischemia: a preplanned analysis of AMESI study.  
Protocol number: 1 
Study Design/Methodology: Prospective multicenter observational study 
Study duration (recruitment period): 06 June 2022 – 05 April 2023 
 
Objectives: The primary objective of this study is to describe the demographic profile, 
clinical presentation, and laboratory findings of patients with non-occlusive mesenteric 
ischemia (NOMI). The secondary objective is to find independent risk factors for NOMI and 
to outline the diagnostics, management strategies, and outcomes of these patients, including 
in-hospital results and outcomes at 90 days and one year.  
Number of subjects: Patients with NOMI (n= 55), arterial occlusive AMI (n=231), venous 
occlusive AMI (n=73), unclear mechanism of AMI (n=48) and patients with suspected but 
not confirmed AMI (n=159), in total 566 patients. 2 
Eligibility criteria: all at least 18-year-old patients with acute mesenteric ischemia or patients 
suspected of acute mesenteric ischemia that was not confirmed.  
 
 

 
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Background 
The current study is a preplanned substudy of a prospective observational multicenter study: 
Incidence, diagnosis, management and outcome of acute mesenteric ischemia: a prospective, 
multicenter observational study (AMESI Study) [1].  
Non-occlusive mesenteric ischemia (NOMI) is a subtype of acute mesenteric ischemia (AMI) 
where insufficient mesenteric perfusion occurs without occlusion of large mesenteric arteries 
[2]. AMI is a rare condition. According to a systematic review and meta-analysis published in 
2022, the mean incidence was 6.2 cases per 100 000 person-years [3]. Out of all AMI cases, 
NOMI accounts for 7 - 30% [1–5]. NOMI was identified in only 13 of the 32 sites in the 
AMESI study, with proportions varying from 0% to 50%. Furthermore, 11.5% out of all 
confirmed AMI patients had an unclear mechanism, which might represent NOMI. One 
reason for variability in NOMI identification stems from both a lack of awareness and the 
inherent difficulty in diagnosing the disease [6]. Due to its rarity, there is a lack of descriptive 
information available in the literature and consistent demographic, clinical, and laboratory 
patterns are not recognized.  
NOMI is challenging to diagnose due to its non-specific symptoms and lack of large vessel 
occlusion. Clinical examination and routine laboratory tests are of only little value in 
reaching an early and reliable diagnosis of NOMI [5]. Computed tomography (CT) 
angiography is considered a gold standard for detecting arterial occlusive mesenteric 
ischemia [7]. Unfortunately, the diagnostic accuracy of CT angiography in detecting NOMI is 
relatively low. In a study by Bourcier et al., 25% of patients diagnosed with NOMI showed 
no signs of mesenteric ischemia on the CT scan [8,9]. One of the reasons for this is the 
absence of specific diagnostic criteria [5]. The diagnostic ambiguity means the true incidence 
of NOMI could be higher than currently reported. By outlining the diagnostic patterns 
observed in patients with NOMI, we may uncover clinical, imaging, or laboratory findings 
that improve the recognition of this condition.  
There are currently no specific management guidelines for NOMI. Consequently, the 
treatment of this condition is based on limited evidence and varies across different 
institutions and clinicians [5]. Describing the management of NOMI patients might contribute 
to the development of more systematic and evidence-based management strategies.  
The aim of this substudy is to describe the demographic profile, clinical presentation, and 
laboratory findings of patients with non-occlusive mesenteric ischemia in comparison to 

 
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other subtypes of acute mesenteric ischemia and patients with suspected but not confirmed 
acute mesenteric ischemia. Furthermore, we aim to identify independent risk factors of 
NOMI and to describe the diagnostics, management strategies, and outcomes of these 
patients.  
 
Study questions 
1. What are the differences in demography, chronic and acute health conditions, clinical 
symptoms, laboratory values, time factors, diagnostics, management, and outcomes 
between patients with NOMI and those with other subtypes (arterial occlusive, 
venous) of AMI? 
2. What are the differences in demography, chronic and acute health conditions, clinical 
symptoms, laboratory values, time factors, and outcomes between patients with 
NOMI and AMI with an unclear mechanism? 
3. Which demographic, chronic and acute health conditions, clinical symptoms, and 
laboratory values are independently associated with NOMI compared to patients with 
suspected but not confirmed AMI? 
3.1.Subgroup analysis: NOMI vs suspected but not confirmed AMI in the ICU 
patients.  
4. Which diagnostic methods are used to identify NOMI, and which for AMI with an 
unclear mechanism?  
5. Which management strategies are used for NOMI, and which for AMI with an unclear 
mechanism? 
6. What are the differences in demography, chronic and acute health conditions, clinical 
symptoms, laboratory values, and outcomes between NOMI patients managed 
surgically and conservatively? 
6.1. Which factors predict the effectiveness of conservative management (survival 
without abdominal surgery)? 
7. What are the outcomes in patients with NOMI? 
8. What are the risk factors of mortality in patients with NOMI?  
7.1. What are the risk factors of mortality in patients with NOMI who received 
treatment without withdrawal of care? 
Study design and methods 

 
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Inclusion criteria for the substudy 
- 
Patients with arterial occlusive AMI 
- 
Patients with non-occlusive mesenteric ischemia 
- 
Patients with venous occlusive AMI 
- 
Patients with unclear mechanism of AMI 
- 
Patients with suspected but not confirmed AMI 
Exclusion criteria for the substudy 
- 
Patients with other specific form of AMI (e.g dissection) 
- 
Confirmed strangulating bowel obstruction 
Study groups 
- 
Patients with non-occlusive mesenteric ischemia. 
- 
Patients with arterial occlusive AMI 
- 
Patients with venous occlusive AMI 
- 
Patients with unclear mechanism of AMI 
- 
Patients with suspected but not confirmed AMI 
- 
Patients with suspected but not confirmed acute mesenteric ischemia 
- 
Patients with suspected but not confirmed acute mesenteric ischemia 
treated in the ICU 
The comparative groups are presented in Annex 1, and the variables included in the study are 
presented in Annex 2. 
 
Study question analysis 
1. What are the differences in demography, chronic and acute health conditions, clinical 
symptoms, laboratory values, time factors, diagnostics, management, and outcomes 
between patients with NOMI and those with other subtypes (arterial occlusive, 
venous) of AMI? 
Patients with NOMI, arterial occlusive, venous occlusive AMI will be analysed. These 
patients will be divided into groups – NOMI vs other subtypes (arterial occlusive, venous 
occlusive) of AMI. The groups (NOMI vs arterial occlusive; NOMI vs venous occlusive) will 
be compared with each other. Normality will be assessed with the Kolmogrov-Smirnov test. 

 
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If the variables follow a normal distribution, means and standard deviations will be used to 
present the data. However, if the data is not normally distributed, medians and interquartile 
ranges will be used instead. Categorical data will be represented with n (%). To compare the 
two groups, a t-test, a Chi-square test, or Mann-Whitney U test will be used. Statistical 
significance will be defined as p < 0.05. 
Parameters used for analysis are depicted in Annex 2 subsections, A. NOMI vs arterial 
occlusive AMI and B. NOMI vs venous occlusive AMI. The variables included are the 
following: demographic description, chronic health conditions, acute health conditions, 
symptoms supporting AMI diagnosis, laboratory values, time factors, diagnostics, 
management, and outcomes.  
2. What are the differences in demography, chronic and acute health conditions, clinical 
symptoms, laboratory values, time factors, and outcomes between patients with 
NOMI and AMI with an unclear mechanism? 
Patients with NOMI and unclear mechanism of AMI will be analysed. These patients will be 
divided into groups – NOMI vs unclear mechanism of AMI. The two groups will be 
compared with each other. Normality will be assessed with the Kolmogrov-Smirnov test. If 
the variables follow a normal distribution, means and standard deviations will be used to 
present the data. However, if the data is not normally distributed, medians and interquartile 
ranges will be used instead. Categorical data will be represented with n (%). To compare the 
two groups, a t-test, a Chi-square test, or Mann-Whitney U test will be used. Statistical 
significance will be defined as p < 0.05. 
Parameters used for analysis are depicted in Annex 2 subsection C. NOMI vs unclear 
mechanism of AMI. The following categories are included: demographic description, chronic 
health conditions, acute health conditions, symptoms supporting AMI diagnosis, laboratory 
values, time factors, and outcomes.  
3. Which demographic, chronic and acute health conditions, clinical symptoms, and 
laboratory values are independently associated with NOMI compared to patients with 
suspected but not confirmed AMI? 
All NOMI patients and those with suspected but not confirmed AMI will be included in the 
analysis. These patients will be divided into groups – NOMI vs suspected but not confirmed 
AMI. The two groups will be compared with each other. A separate subgroup comparison will 

 
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be conducted between patients with NOMI and ICU patients with suspected but not 
confirmed AMI. Normality will be assessed with the Kolmogrov-Smirnov test. If the 
variables follow a normal distribution, means and standard deviations will be used to present 
the data. However, if the data is not normally distributed, medians and interquartile ranges 
will be used instead. Categorical data will be represented with n (%). To compare the two 
groups, a t-test, a Chi-square test, or Mann-Whitney U test will be used. Statistical 
significance will be defined as p < 0.05. 
To find demographic, acute, and chronic health variables, symptoms, and laboratory tests that 
are independently associated with the occurrence of NOMI, univariable regression models for 
the occurrence of NOMI will be fitted. All risk factors with p-value < 0.1 will be entered into 
multivariate regression model to determine the independent associations. Variables showing 
p-values < 0.05 in the multivariable model will be considered independent risk factors for the 
occurrence of NOMI.  
Parameters used for analysis are depicted in Annex 2 subsection D. NOMI vs suspected but 
not confirmed AMI and E. NOMI vs suspected but not confirmed AMI in the ICU. The 
following categories are included: demographic description, chronic health conditions, acute 
health conditions, symptoms supporting AMI diagnosis, and laboratory values.  
 
4. Which diagnostic methods are used to identify NOMI, and which for AMI with an 
unclear mechanism?  
Patients with NOMI and unclear mechanism of AMI will be analysed. These patients will be 
divided into groups – NOMI vs unclear mechanism of AMI. The two groups will be 
compared with each other. Data will be presented as numbers and proportions. To compare 
the two groups, the Chi-square test or Fisher’s exact test will be used, as appropriate. 
Statistical significance will be defined as p < 0.05. 
Parameters used for analysis are depicted in Annex 2 subsection C. NOMI vs unclear 
mechanism of AMI. Only the diagnostics category will be included in the analysis.   
5. Which management strategies are used for NOMI, and which for AMI with an unclear 
mechanism? 

 
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Patients with NOMI and unclear mechanism of AMI will be analysed. These patients will be 
divided into groups – NOMI vs unclear mechanism of AMI. The two groups will be 
compared with each other. Data will be presented as numbers and proportions. To compare 
the two groups, the Chi-square test or Fisher’s exact test will be used, as appropriate. 
Statistical significance will be defined as p < 0.05. 
Parameters used for analysis are depicted in Annex 2 subsection C. NOMI vs unclear 
mechanism of AMI. Only the management category will be included in the analysis.   
6. What are the differences in demography, chronic and acute health conditions, clinical 
symptoms, laboratory values, and outcomes between NOMI patients managed 
surgically vs conservatively? 
All patients with NOMI will be included in the analysis. NOMI patients will be separated into 
two groups based on management – surgical vs conservative. Data will be presented as 
numbers and proportions. A separate subgroup comparison will be made between patients 
with effective conservative management (defined as hospital survival without surgical 
intervention) and those who died during conservative management or required surgical 
intervention after initial conservative management. For continuous variables normality will 
be assessed with the Kolmogrov-Smirnov test. If the variables follow a normal distribution, 
means and standard deviations will be used to present the data. However, if the data is not 
normally distributed, medians and interquartile ranges will be used instead. To compare the 
two groups, a t-test, Chi-square test, or Mann-Whitney U test will be used. Statistical 
significance will be defined as p < 0.05. 
Parameters used for analysis are depicted in Annex 2 subsections, F. Conservatively managed 
NOMI vs surgically managed NOMI and G. Effective conservative NOMI management vs 
ineffective conservative and surgically managed. The following categories are included: 
demographic description, chronic health conditions, acute health conditions, symptoms 
supporting NOMI diagnosis, laboratory values, and outcomes.  
7. What are the outcomes in patients with NOMI?  
Only patients with NOMI will be analysed. Data will be presented as numbers and 
proportions. If the variables follow a normal distribution, means and standard deviations will 
be used to present the data. However, if the data is not normally distributed, medians and 
interquartile ranges will be used instead. 

 
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Parameters used for analysis are depicted in Annex 2 subsection H. NOMI outcomes. Only 
the outcomes category will be included in the analysis. 
8. What are the risk factors of mortality in patients with NOMI?  
Only patients with NOMI will be analysed. To find the potential risk factors we will enter all 
potential risk factors for mortality among NOMI patients into univariable model. A separate 
subgroup analysis will be performed among NOMI patients who received treatment without 
withdrawal of care. All variables showing p-values <0.1 will be entered into multivariable 
regression model to determine the independent associations. Variables showing p-value < 
0.05 will be considered independent risk factors for mortality among NOMI patients.  
Parameters used for analysis are depicted in Annex 2 subsections, I. Surviving NOMI vs 
deceased NOMI and J. Surviving NOMI vs deceased NOMI without withdrawal of care. 
NOMI. The following categories are included: demographic description, chronic health 
conditions, acute health conditions, symptoms supporting NOMI diagnosis, laboratory 
values, time factors, management, and ICU management.  
 
Ethical considerations 
Since this is an analysis of a pseudonymized database from an Ethics Committee approved 
study (EC of the University of Tartu, 357/T-8 and 364M-7), no separate ethical approval is 
required. 
 
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and outcomes of acute mesenteric ischaemia: a systematic review and meta-analysis. BMJ 
Open. BMJ Publishing Group; 2022.  

 
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