Normal Lactate and Unenhanced CT-Scan Result in Delayed Diagnosis of Acute Mesenteric Ischemia

Insights into acute mesenteric ischaemia: an up-to-date, evidence-based review from a mesenteric stroke centre unit

Radiologists play a central role in the diagnostic and prognostic evaluation of patients with acute mesenteric ischaemia (AMI). Unfortunately, more than half of AMI patients undergo imaging with no prior suspicion of AMI, making identifying this disease even more difficult. A confirmed diagnosis of AMI is ideally made with dynamic contrast-enhanced CT but the diagnosis may be made on portal-venous phase images in appropriate clinical settings. AMI is diagnosed on CT based on the identification of vascular impairment and bowel ischaemic injury with no other cause. Moreover, radiologists must evaluate the probability of bowel necrosis, which will influence the treatment options.AMI is usually separated into different entities: arterial, venous, non-occlusive and ischaemic colitis. Arterial AMI can be occlusive or stenotic, the dominant causes being atherothrombosis, embolism and isolated superior mesenteric artery (SMA) dissection. The main finding in the bowel is decreased wall enhancement, and necrosis can be suspected when dilatation >25 mm is identified. Venous AMI is related to superior mesenteric vein (SMV) thrombosis as a result of a thrombophilic state (acquired or inherited), local injury (cancer, inflammation or trauma) or underlying SMV insufficiency. The dominant features in the bowel are hypoattenuating wall thickening with submucosal oedema. Decreased enhancement of the involved bowel suggests necrosis. Non-occlusive mesenteric ischaemia (NOMI) is related to impaired SMA flow following global hypoperfusion associated with low-flow states. There are numerous findings in the bowel characterised by diffuse extension. An absence of bowel enhancement and a thin bowel wall suggest necrosis in NOMI. Finally, ischaemic colitis is a sub-entity of arterial AMI and reflects localised colon ischaemia-reperfusion injury. The main CT finding is a thickened colon wall with fat stranding, which seems to be unrelated to SMA or inferior mesenteric artery lesions. A precise identification and description of vascular lesions, bowel involvement and features associated with transmural necrosis is needed to determine patient treatment and outcome.

Acute mesenteric ischemia: which predictive factors of delayed diagnosis at emergency unit?

PURPOSE

Acute mesenteric ischemia (AMI) is frequently diagnosed late, leading to a poor prognosis. Our aims were to identify predictive factors of delayed diagnosis and to analyze the outcomes of patients with AMI admitted in emergency units.

METHODS

All the patients with AMI (2015-2020), in two Emergency units, were retrospectively included. Two groups were defined according to the time of diagnosis between the arrival at emergency unit and the CT scan: ≤ 6 h (early), > 6 h (delayed).

RESULTS

119 patients (mean age = 71 ± 7 years) were included. The patients with a delayed diagnosis (n = 33, 28%) were significantly associated with atypical presentation, including lower rates of abdominal pain (73 vs 89%, p = 0.003), abdominal tenderness (33 vs 43%, p = 0.03), and plasma lactate (4 ± 2 vs 6 ± 7 mmol/l, p = 0.03) when compared with early diagnosis. After multivariate analysis, the absence of abdominal pain was the only independent predictive factor of delayed diagnosis (Odd Ratio = 0.17; 95% CI = 0.03-0.88, p = 0.03). Patients with delayed diagnosis tended to be associated to lower rates of revascularization (9 vs 17%, p = 0.4), higher rates of major surgical morbidity (90 vs 57%, p = 0.1), longer length of stay (16 ± 23 vs 13 ± 15 days, p = 0.4) and, at the end of follow-up, higher rate of short small bowel syndrome (18 vs 7%, p = 0.095).

CONCLUSION

AMI is a challenge for emergency physicians. History of patient, physical exam, biological data are not sufficient to diagnose AMI. New biomarkers, and awareness of emergency physicians should improve and accelerate the diagnosis of AMI.

Improving clinical suspicion of acute mesenteric ischemia among patients with acute abdomen: a cross-sectional study from an intestinal stroke center

BACKGROUND

Early diagnosis of acute mesenteric ischemia (AMI) is essential for a favorable outcome. Selection of patients requiring a dedicated multiphasic computed tomography (CT) scan remains a clinical challenge.

METHODS

In this cross-sectional diagnostic study conducted from 2016 to 2018, we compared the presentation of AMI patients admitted to an intestinal stroke center to patients with acute abdominal pain of another origin admitted to the emergency room (controls).

RESULTS

We included 137 patients-52 with AMI and 85 controls. Patients with AMI [median age: 65 years (interquartile range 55-74)] had arterial and venous AMI in 65% and 35% of cases, respectively. Relative to controls, AMI patients were significantly older, more likely to have risk factors or a history of cardiovascular disease, and more likely to present with sudden-onset and morphine-requiring abdominal pain, hematochezia, guarding, organ dysfunction, higher white blood cell and neutrophil counts, and higher plasma C-reactive protein (CRP) and procalcitonin concentrations. On multivariate analysis, two independent factors were associated with the diagnosis of AMI: the sudden-onset (OR = 20, 95%CI 7-60, p < 0.001) and the morphine-requiring nature of the acute abdominal pain (OR = 6, 95%CI 2-16, p = 0.002). Sudden-onset and/or morphine-requiring abdominal pain was present in 88% of AMI patients versus 28% in controls (p < 0.001). The area under the receiver operating characteristic curve for the diagnosis of AMI was 0.84 (95%CI 0.77-0.91), depending on the number of factors.

CONCLUSIONS

Sudden onset and the need for morphine are suggestive of AMI in patients with acute abdominal pain and should prompt multiphasic CT scan including arterial and venous phase images for confirmation.

Increased blood lactate during enteral nutrition in the critically ill: associations and treatment options

PURPOSE OF REVIEW

To evaluate the significance of blood lactate increase during enteral nutrition in the critically ill, and to propose diagnostic and therapeutic strategies.

RECENT FINDINGS

Acute mesenteric ischemia occurs in approximately 1% of critically ill patients treated with catecholamine. Recent literature suggests that enteral nutrition is a risk factor of acute mesenteric ischemia, in particular in case of low cardiac output, by a mechanism of nonocclusive mesenteric ischemia. The association of clinical, biological, and computed tomography imaging might help to evaluate the reversibility of acute mesenteric ischemia.

SUMMARY

As enteral nutrition induces an increased metabolic work of the gut, the inadequation between oxygen delivery and demand exposes the gut to a phenomenon of nonocclusive mesenteric ischemia. Before initiation of enteral nutrition,, and before each increase of the enteral nutrition dose, the risk factors of nonocclusive mesenteric ischemia should be searched in order to prevent it. While under enteral nutrition, increased lactate concentration while receiving enteral nutrition requires the urgent search for nonocclusive mesenteric ischemia, and the adaptation of enteral nutrition (reduction, stop, and/or switch to parenteral nutrition or tolerate early nutrient restriction). Early signs of nonocclusive mesenteric ischemia should be searched in order to allow for a rapid diagnosis, before development of irreversible transmural necrosis. After the diagnosis of acute mesenteric ischemia, improving the balance between oxygen demand and delivery to the gut, evaluating the reversibility of the gut ischemia, and performing urgent resection in case of irreversible transmural necrosis should be the main objectives. After the resolution of acute mesenteric ischemia, the benefit risk analysis of enteral nutrition reintroduction should be evaluated.

MRI for the Detection of Small Bowel Ischemic Injury in Arterial Acute Mesenteric Ischemia: Preclinical Study in a Porcine Model

BACKGROUND

MRI is the reference for the diagnosis of arterial cerebral ischemia, but its role in acute mesenteric ischemia (AMI) is poorly known.

PURPOSE

To assess MRI detection of early ischemic bowel lesions in a porcine model of arterial AMI.

STUDY TYPE

Prospective/cohort.

ANIMAL MODEL

Porcine model of arterial AMI obtained by embolization of the superior mesenteric artery (seven pigs).

FIELD STRENGTH/SEQUENCE

A 5-T. T1 gradient-echo-weighted-imaging (WI), half-Fourier-acquisition-single-shot-turbo-spin-echo, T2 turbo-spin-echo, true-fast-imaging-with-steady-precession (True-FISP), diffusion-weighted-echo-planar (DWI).

ASSESSMENT

T1-WI, T2-WI, and DWI were performed before and continuously after embolization for 6 hours. The signal intensity (SI) of the ischemic bowel was assessed visually and quantitatively on all sequences. The apparent diffusion coefficient (ADC) was assessed.

STATISTICAL TESTS

Paired Student's t-test or Mann-Whitney U-test, significance at P < 0.05.

RESULTS

One pig died from non-AMI-related causes. The remaining pigs underwent a median 5 h53 (range 1 h24-6 h01) of ischemia. Visually, the ischemic bowel showed signal hyperintensity on DWI-b800 after a median 85 (57-276) minutes compared to the nonischemic bowel. DWI-b800 SI significantly increased after 2 hours (+19%) and the ADC significant decrease within the first hour (-31%). The ischemic bowel was hyperintense on precontrast T1-WI after a median 87 (70-171) minutes with no significant quantitative changes over time (P = 0.46-0.93). The ischemic bowel was hyperintense on T2-WI in three pigs with a significant SI increase on True-FISP after 1 and 2 hours.

DATA CONCLUSION

Changes in SI and ADC can be seen early after the onset of arterial AMI with DWI. The value of T2-WI appears to be limited.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

Basic demographic characteristics and prevalence of comorbidities in acute mesenteric ischemia: a systematic review and proportional meta-analysis

PURPOSE

The aim of this systematic review and meta-analysis was to examine and assess the basic demographic characteristics and prevalence of comorbidities in acute mesenteric ischemia (AMI) and its various subtypes.

PATIENTS AND METHODS

A literature search was conducted by using the databases PubMed, EMBASE, and Google Scholar (to June 1, 2022). Random-effects or fixed-effects models were selected to pool means and proportions and their corresponding 95% confidence intervals (CI), based on heterogeneity between studies. The results of meta-analyses for basic demographic characteristics and prevalence (proportions) of each specific comorbidities of acute mesenteric ischemia (AMI) and its various subtypes were described.

RESULTS

Ninety-nine studies were included in the meta-analysis, including 17,103 patients with AMI. Furthermore, 7941 patients with subclass diagnoses of AMI were identified, including 3,239 patients with arterial occlusive mesenteric ischemia (AOMI), 2,977 patients with nonocclusive mesenteric ischemia (NOMI), and 1,725 patients with mesenteric venous thrombosis (MVT). As a surgical emergency, AMI is associated with older patients and a high likelihood of multisystem comorbidities. Comorbidities of AMI involved multiple systemic diseases, including cardiovascular disease, endocrine and metabolic diseases, kidney diseases, digestive diseases, respiratory diseases, cerebrovascular diseases, vascular diseases, and cancer.

CONCLUSION

The basic demographic characteristics and the prevalence of comorbidities of different subtypes of AMI are different. The management of comorbidities should be an essential part of improving the prognosis of AMI patients and may contribute to precise prevention of AMI.

Role of clinical data and multidetector computed tomography findings in acute superior mesenteric artery embolism

BACKGROUND

Superior mesenteric artery embolism (SMAE) has acute onset and fast progression, which seriously threatens the life of patients. Multidetector computed tomography (MDCT) is one of the most important diagnostic methods for SMAE, which plays an important role in the diagnosis and prognosis of SMAE.

AIM

To evaluate the value of combined clinical data and MDCT findings in the diagnosis of acute SMAE and predict the risk factors for SMAE-related death.

METHODS

Data from 53 SMAE patients who received abdominal MDCT multi-phase enhancement and superior mesenteric artery digital subtraction angiography examinations were collected. Univariate cox regression and multivariate cox model were used to analyze the correlation between death risk and clinical and computed tomography features in SMAE patients.

RESULTS

Univariate Cox regression model showed that intestinal wall thinning, intestinal wall pneumatosis, blood lactate > 2.1 mmol/L and blood pH < 7.35 increased the risk of death in patients with SMAE. After adjusting for age, sex, embolic involvement length and embolic distribution region, multivariate Cox regression model I showed that blood lactate > 2.1 mmol/L (HR = 5.26, 95%CI: 1.04-26.69, P = 0.045) and intestinal wall thinning (HR = 9.40, 95%CI: 1.05-83.46, P = 0.044) were significantly increases the risk of death in patients with SMAE.

CONCLUSION

For patients with SAME, increased blood lactate and intestinal wall thinning are the risk factors for death; hence, close monitoring may reduce the mortality rate. Clinical observation combined with MDCT signs can significantly improve SMAE diagnosis.

Colonic involvement in acute mesenteric ischemia: prevalence, risk factors, and outcomes

OBJECTIVES

This study aimed to investigate the prevalence, risk factors, and outcomes of colonic involvement in patients with acute mesenteric ischemia (AMI).

METHODS

CT scans from a prospective cohort of 114 AMI patients treated in an intestinal stroke center between 2009 and 2018 were blindly reviewed by two radiologists. Colon involvement was defined on CT scan by the presence of at least one of the following CT colonic features: wall thickening, pneumatosis, decreased wall enhancement, dilatation, or perforation. In addition, the clinical, biological, and radiological characteristics of patients with and without colonic involvement were compared to identify risk factors for colonic involvement on CT and its impact on morbidity and mortality.

RESULTS

Colonic involvement was identified in 32/114 (28%) patients with AMI, the right colon being more frequently involved (n = 29/32, 91%). Wall thickening (n = 27/32) was the most common CT finding. Occlusion of the inferior mesenteric artery was the only statistically significant risk factor for colonic involvement (35% vs. 15%, p = 0.02). Patients with colonic involvement on CT vs. those without had more frequently transmural colonic necrosis (13% vs. 0%, p = 0.006), short bowel syndrome (16% vs. 4%, p = 0.04), need for long-term parenteral support (19% vs. 5%, p = 0.03), and death during follow-up (22% vs. 10%, p = 0.03).

DISCUSSION

In patients with AMI, colonic involvement is associated with increased morbidity and mortality and should be carefully searched for during initial CT scan assessment.

KEY POINTS

• In a prospective cohort of acute mesenteric ischemia patients from an intestinal stroke center, 28% had an associated colonic involvement on CT. • Colonic involvement on CT most commonly affected the right colon, and the occlusion of the inferior mesenteric artery was the only risk factor. • Colonic involvement on CT was associated with increased morbidity and mortality and should be carefully searched for during initial CT scan assessment.

l-lactate kinetics after abdominal aortic surgery and intestinal ischemia - An observational cohort study

BACKGROUND

Postoperative intestinal ischemia is a severe complication in abdominal aortic surgery. Early diagnosis is needed for adequate and timely treatment. We studied the postoperative kinetics of l-lactate in vascular patients to assess its value as a marker for early postoperative intestinal ischemia detection.

MATERIAL AND METHODS

We performed a prospective non-randomized single-center observational cohort study in eighty elective patients, fifty operated on for abdominal aortic aneurysm (AAA) and thirty for aortoiliac occlusive disease (AIOD). Serum l-lactate was measured preoperatively, intraoperatively, and postoperatively at defined timepoints up to postoperative day 7. Intestinal ischemia was detected using MRI enterocolography. We have used univariate logistic regression and receiver operating characteristics curves for the evaluation of marker accuracy.

RESULTS

We recorded 6 cases of postoperative intestinal ischemia (7.5%), five non-transmural and one transmural. Two patients died because of this complication (mortality 33%). The comparison of AAA and AIOD cohorts showed a significant difference in l-lactate levels at one intraoperative timepoint, which was attributable to procedure differences. The only preoperative factor associated with higher l-lactate levels at some timepoints was chronic kidney disease. Patients suffering postoperative intestinal ischemia had elevated serum l-lactate levels at multiple timepoints. The most accurate timepoint for diagnosis was 24 h after the declamping of the vascular reconstruction (DC24H), the second was 10 min after declamping. Sensitivity, specificity, positive and negative predictive values at timepoint DC24H were 100%, 82%, 32%, and 100%, respectively.

CONCLUSION

Serum l-lactate levels might help in the early detection of postoperative intestinal ischemia after aortic surgery if proper timepoints are used. Cutoff values need to be established in large-scale prospective studies.

Hospital-based Delays to Revascularization Increase Risk of Post-operative Mortality and Short Bowel Syndrome in Acute Mesenteric Ischemia

OBJECTIVE

Acute mesenteric ischemia (AMI) is a surgical emergency for which delays in treatment have been closely associated with high morbidity and mortality. Although the duration of ischemia as a determinant of outcomes for AMI is well known, the objective of this study was to identify hospital-based determinants of delayed revascularization and their effects on post-operative morbidity and mortality in AMI.

METHODS

All patients who underwent any surgery for acute mesenteric ischemia (AMI) from a multi-center hospital system between 2010 and 2020 were divided into two groups based on timeliness of mesenteric revascularization after presentation. Early revascularization (ER) was defined as having both vascular consultation ≤ 12 hours of presentation and vascular surgery performed at the patient's initial operation. Delayed revascularization (DR) was defined as having either delays to vascular consultation or vascular surgery. A retrospective review of demographic and post-operative data was performed. Effect of DR on major post-operative outcomes including 30-day and 2-year mortality, total length of bowel resection, and development of short bowel syndrome were analyzed. Effects of delayed vascular consultation alone, delayed vascular surgery alone, no revascularization during admission, and admitting service on outcomes were also examined on sub-group analyses.

RESULTS

A total of 212 patients were analyzed. 99 patients received ER while the remaining 113 patients experienced a delay to revascularization after hospital presentation. Among the DR group, 55 (25.9%) patients had delayed vascular consultation while vascular surgery was deferred until after the initial operation in 37 (17.4%) patients. 51 (24.0%) patients were never revascularized during admission. DR was a significant predictor of 30-day (odds ratio (OR) 2.09, 95% confidence interval (CI) [1.4-4.9], P=0.03) and 2-year mortality (hazard ratio (HR) 1.55, CI [1.0-2.3], P= 0.04). DR was also independently associated with increased bowel resection length (OR 7.47, P <0.01) and post-operative short bowel syndrome (OR 2.4, P=0.03) on multivariate analyses. When examined separately on sub-group analysis, both delayed vascular consultation (OR 3.38, P=0.03) and vascular surgery (OR 4.31, P <0.01) independently increased risk of 30-day mortality. Hospital discharge after AMI without mesenteric revascularization was associated with increased risk of short bowel syndrome (OR 2.94, P <0.01) and late mortality (HR 1.60, P=0.04).

CONCLUSIONS

Delayed vascular consultation and vascular surgery are both significant hospital-based determinants of post-operative mortality and short bowel syndrome in AMI. Timing-based management protocols which emphasize routine evaluation by a vascular surgeon and early, definitive mesenteric revascularization should be established and widely adopted for all patients with clinically suspected AMI at presentation.

Evaluating the Risk of Irreversible Intestinal Necrosis Among Critically Ill Patients With Nonocclusive Mesenteric Ischemia

INTRODUCTION

To identify factors associated with irreversible transmural necrosis (ITN) among critically ill patients experiencing nonocclusive mesenteric ischemia (NOMI) and to compare the predictive value regarding ITN risk stratification with that of the previously described Clichy score.

METHODS

All consecutive patients admitted to the intensive care unit between 2009 and 2019 who underwent exploratory laparotomy for NOMI and who had an available contrast-enhanced computed tomography with at least 1 portal venous phase were evaluated for inclusion. Clinical, laboratory, and radiological variables were collected. ITN was assessed on pathological reports of surgical specimens and/or on laparotomy findings in cases of open-close surgery. Factors associated with ITN were identified by univariate and multivariate analysis to derive a NOMI-ITN score. This score was further compared with the Clichy score.

RESULTS

We identified 4 factors associated with ITN in the context of NOMI: absence of bowel enhancement, bowel thinning, plasma bicarbonate concentration ≤15 mmol/L, and prothrombin rate <40%. These factors were included in a new NOMI-ITN score, with 1 point attributed for each variable. ITN was observed in 6%, 38%, 65%, 88%, and 100% of patients with NOMI-ITN score ranging from 0 to 4, respectively. The NOMI-ITN score outperformed the Clichy score for the prediction of ITN (area under the receiver operating characteristics curve 0.882 [95% confidence interval 0.826-0.938] vs 0.674 [95% confidence interval 0.582-0.766], respectively, P < 0.001).

DISCUSSION

We propose a new 4-point score aimed at stratifying risk of ITN in patients with NOMI. The Clichy score should be applied to patients with occlusive acute mesenteric ischemia only.

A rapid preliminary prediction model for intestinal necrosis in acute mesenteric ischemia: a retrospective study

BACKGROUND

Acute mesenteric ischemia (AMI) is a life-threatening condition. However, there is no accurate method to predict intestinal necrosis in AMI patients that may facilitate early surgical intervention. This study thus aimed to explore a simple and accurate model to predict intestinal necrosis in patients with AMI.

METHODS

A single-center retrospective study was performed on the data of 132 AMI patients treated between October 2011 and June 2020. The patients were divided into the intestinal necrosis and non-intestinal necrosis groups. The clinical characteristics and laboratory data were analyzed by univariate analysis, and the variables with statistical significance were further analyzed by multivariate logistic regression analysis. The independent predictors of intestinal necrosis were determined and a logistic prediction model was established. Finally, the accuracy, sensitivity, and specificity of the model in predicting intestinal necrosis were evaluated.

RESULTS

Univariate analysis showed that white blood cell (WBC) count, blood urea nitrogen (BUN) level, neutrophil ratio, prothrombin time (PT), and LnD-dimer were associated with intestinal necrosis. According to logistic regression multivariate analysis, WBC count, BUN level and LnD-dimer were independent predictors of intestinal necrosis. These parameters were used to establish a clinical prediction model of intestinal necrosis (CPMIN) as follows: model score = 0.349 × BUN (mmol/L) + 0.109 × WBC × 109 (109/L) + 0.394 × LnD - Dimer (ug/L) - 7.883. The area under the receiver operating characteristics (ROC) curve of the model was 0.889 (95% confidence interval: 0.833-0.944). Model scores greater than - 0.1992 predicted the onset of intestinal necrosis. The accuracy, specificity, and sensitivity of the model were 82.6%, 78.2%, and 88.3%, respectively. The proportion of intestinal necrosis in the high-risk patient group (CPMIN score ≥ - 0.1992) was much greater than that in the low-risk patient group (CPMIN score < - 0.1992; 82.7% vs. 15.0%, p < 0.001).

CONCLUSION

The CPMIN can effectively predict intestinal necrosis and guide early surgical intervention to improve patient prognosis. Patients with AMI who are classified as high-risk should be promptly treated with surgery to avoid the potential complications caused by delayed operation. Patients classified as low-risk group can receive non-surgical treatment. This model may help to lower the morbidity and mortality from AMI. However, this model's accuracy should be validated by larger sample size studies in the future.

A clinical approach to acute mesenteric ischemia

PURPOSE OF REVIEW

To summarize current evidence on acute mesenteric ischemia (AMI) in critically ill patients, addressing pathophysiology, definition, diagnosis and management.

RECENT FINDINGS

A few recent studies showed that a multidiscipliary approach in specialized centers can improve the outcome of AMI. Such approach incorporates current knowledge in pathophysiology, early diagnosis with triphasic computed tomography (CT)-angiography, immediate endovascular or surgical restoration of mesenteric perfusion, and damage control surgery if transmural bowel infarction is present. No specific biomarkers are available to detect early mucosal injury in clinical setting. Nonocclusive mesenteric ischemia presents particular challenges, as the diagnosis based on CT-findings as well as vascular management is more difficult; some recent evidence suggests a possible role of potentially treatable stenosis of superior mesenteric artery and beneficial effect of vasodilator therapy (intravenous or local intra-arterial). Medical management of AMI is supportive, including aiming of euvolemia and balanced systemic oxygen demand/delivery. Enteral nutrition should be withheld during ongoing ischemia-reperfusion injury and be started at low rate after revascularization of the (remaining) bowel is convincingly achieved.

SUMMARY

Clinical suspicion leading to tri-phasic CT-angiography is a mainstay for diagnosis. Diagnosis of nonocclusive mesenteric ischemia and early intestinal injury remains challenging. Multidisciplinary team effort may improve the outcome of AMI.