Acute Mesenteric Ischemia with Air Embolism in the Superior Mesenteric Artery: A Rare Case and a Literature Review

Abstract

Background: Acute mesenteric ischemia (AMI) is a potentially life-threatening condition that requires prompt diagnosis and treatment. The presence of air within the arterial lumen, particularly in the abdomen, is an uncommon finding with varied etiologies. This case report presents a unique instance of AMI with air in the superior mesenteric artery (SMA), highlighting the complexities in diagnosis and management. Case presentation: An 89-year-old male with a history of smoking, hypertension, dyslipidemia, and atrial fibrillation presented with chest pain and underwent coronary angiography for suspected anterior ST-elevation myocardial infarction (STEMI). Following successful thromboaspiration and admission to the coronary care unit, he developed severe abdominal pain. A contrast-enhanced computed tomography (CECT) scan revealed a thromboembolic occlusion in the SMA, along with air filling in the SMA and its branches. An endovascular thrombectomy was performed, but the patient died the next day due to complications related to AMI and metabolic acidosis. Conclusions: This case underscores the challenges in diagnosing and managing AMI, particularly when accompanied by unusual imaging findings such as air within the SMA. The presence of air in the arterial system raises questions about its origin and clinical significance in the context of AMI. Further research is needed to understand the mechanisms and implications of this rare phenomenon, which may have implications for refining diagnostic and therapeutic strategies for AMI.

1. Background

Acute mesenteric ischemia (AMI) is an emergency that accounts for about 2% of all pathological conditions of the gastrointestinal tract [1,2]. It is a condition with high mortality rates (50–90%) which depends on the etiology of the AMI, the degree of ischemia, the extent of the intestinal segment involved, and the time elapsed between the onset of symptoms and diagnosis [2,3]. This is, therefore, a time-dependent condition where early diagnosis and prompt treatment are crucial for improving patient outcomes [3,4].

Diagnosis is complex because signs and symptoms correlate with many other abdominal conditions, making diagnostic suspicion arduous. A CT scan of the abdomen without and with contrast administration is the gold standard in the diagnosis because it makes it possible to evaluate the bowel walls, the material inside the lumen, vessels, and mesenteries, identifying its etiology and severity [4,5].

On the other hand, the presence of air within the arterial lumen is an extremely rare finding, especially in the abdomen, and its origin can be varied.

2. Case Report

We report a case of an 89-year-old male smoker with a history of hypertension, dyslipidemia, and atrial fibrillation, admitted to our hospital with chest pain. After triage and assessment of vital parameters, an electrocardiogram was performed, which raised the suspicion of anteroseptal acute coronary syndrome-ST-elevation myocardial infarction (ACS-STEMI). The patient underwent coronary angiography, which demonstrates thrombotic obstruction of the anterior interventricular artery, successfully treated with thromboaspiration. After treatment, the patient was admitted to the coronary care unit (CCU) and, a few hours after thromboaspiration, began to complain of severe abdominal pain. Physical examination revealed a globular abdomen with superficial and deep tenderness, but the patient was alert and cooperative. Due to the worsening clinical condition, a contrast-enhanced computed tomography scan (CECT) was performed.

The CECT shows the presence of a filling defect, thromboembolic in nature, which affects the superior mesenteric artery, extending for approximately 48 mm and encompassing the origin of the middle colic artery, ileo-colic artery, and the jejunal arteries (Reiner’s critical segment) (Figure 1). This obstruction affects the S2 tract, including some collateral branches, according to the classification proposed by Tual et al. [6]. Moreover, air filling was detected within the most caudal portions of the SMA and its terminal branches downstream of the thrombotic occlusion (Figure 2).

Regarding the bowel findings, signs of arterial ischemic injury were observed in several jejunal and ileal loops, which appeared congregated and anteriorly displaced within the abdominal cavity, with thinned walls (paper-thin sign) and reduced enhancement due to decreased arterial blood flow and distension from intraluminal gas. These findings define a condition of hypotonic ileus (Figure 3). However, there was no evidence of gas in the mesenteric venous system, portal vein, or pneumatosis.

Following the diagnosis of acute mesenteric ischemia, an endovascular thrombectomy was performed.

In the angiography room, after right femoral arterial access with a 7 Fr long vascular sheath, the superior mesenteric artery was catheterized; the diagnostic aortogram confirms the presence of a thrombus in the S2 tract of SMA, with opacification of only the first jejunal branches and middle colic re-inhabiting the colon (Figure 4).

Aspiration of the thrombus was performed through the CAT6 RX Aspiration System (Penumbra Inc., Alameda, CA, USA), after administering 2000 UI of systemic heparin (5000 UI of heparin had already been administered during coronary thromboaspiration).

At the final mesenteric angiography, the revascularization of the colic arteries, jejunal branches, and some ileal branches was documented, with little opacification of the distal branches of the ileum (Figure 4).

Intestinal resection surgery was not carried out, because, in accordance with the opinion of the patient’s relatives and the subject himself, given the subject’s concomitant pathologies, a possible short bowel syndrome, even though he could have avoided sudden death, would not have given him an adequate chance of life, since elderly subjects with many pathologies may not tolerate long-term parenteral nutrition.

Unfortunately, despite the therapeutic management, the patient died the next day because of complications related to acute mesenteric ischemia and metabolic acidosis.

3. Discussion

AMI is an emergency condition caused by a lack of oxygen in the bowel and is associated with a high mortality rate, but it can be challenging to diagnose due to non-specific signs and symptoms [7].

A CECT scan of the abdomen and pelvis is considered the gold standard in diagnosing IMA because it allows assessment of the vasculature, bowel wall, and mesentery. An unenhanced phase (necessary to identify calcifications, clots, and bowel wall hematoma), an arterial phase to visualize the arterial vessels, and a portal venous phase to study the bowel wall are usually performed.

AMI can be classified as arterial occlusive (60–80% of cases), venous occlusive, or nonocclusive mesenteric ischemia (NOMI) caused by a reduction in oxygen perfusion. Different types of acute mesenteric arterial ischemia can be distinguished based on etiology.

In most cases, arterial AMI is due to embolic phenomena, followed, in order of frequency, by AMI associated with the formation of thrombotic plugs superimposed on atherosclerotic plaques, those associated with dissection phenomena of the abdominal aorta and/or superior mesenteric artery, and, finally, those associated with systemic hypoperfusion [8].

In acute mesenteric ischemia, following thromboembolic occlusion of the arterial lumen, there is a progression of damage that allows us to identify several stages.

In the early stage, the intestinal loops, especially those of the small intestine, appear contracted due to the spastic reflex ileus with reduced parietal contrast due to reduced arterial blood supply. In addition, the mesentery appears pale due to the reduced caliber of the tributary arteries [1,3].

In the intermediate stage, blood and fluid are drained from the venous system, and the intestinal walls appear thin with a “paper-like” appearance. Furthermore, the affected bowel walls lose the parietal tone of the previous phase and are exclusively filled with a gaseous component, resulting in a hypotonic ileum [9].

The CT appearance of a hypotonic ileum, with loops distended anteriorly in the abdominal cavity, with thin walls and filled with gas, resembles the appearance of fish “gasping” at the water’s surface when it is deprived of oxygen.

In the final stage, the loops show air–fluid levels, and wall necrosis may result in parietal and venous pneumatosis or pneumoperitoneum and free peritoneal fluid. Bowel sounds are absent at this stage, resulting in the paralytic ileum [9].

Furthermore, in our patient, the CT scan shows the presence of gas exclusively in the SMA (Figure 4) downstream of the thrombotic occlusion, and this finding appears to be uncommon.

Sepsis is the main cause of death in patients with mesenteric ischemia, because intestinal ischemia induces an early loss of the mucosal barrier, increasing the enzymatic activity of digestive serine proteases in the intestinal wall [10]. This process allows bacterial translocation in the intestinal mucosa and submucosa and through circulation to other organs, inducing inflammation and increasing the risk of septic complications [11].

We extensively reviewed the literature on gas in the arterial vessels using the PUBMED database. Keywords used in the search included “ARTERIAL AND AIR EMBOLISM”, “SUPERIOR MESENTERIC ARTERY AND AIR EMBOLISM”, and “SUPERIOR MESENTERIC ARTERY AND GAS”. Excluding systematic reviews, we found only seven articles discussing gas in the splanchnic arterial vessels (

Table 1. Summary of the previously published cases of air embolism in the SMA.

Author	Year	Type of Study	Cause of Air Embolism	Site of Air Embolism	Prognosis
Numata S. et al. [12]	2013	Case report	Acute aortic dissection	SMA	Death
Devos P. et al. [13]	2017	Case report	Endovascular stenting of the superior mesenteric artery	SMA, hepatic artery, and abdominal aorta	No sequels (after hyperbaric chamber session)
Lambert L. et al. [14]	2018	Case report	TEVAR, after type A aortic dissection	Superior mesenteric artery (SMA)	Death
Giulio F. et al. [15]	2022	Case report	Associated with thrombotic disease of the SMA	SMA	Death
Khripun A.I. et al. [16]	2022	Case report	Post-thromboaspiration of thrombotic occlusion in the SMA	SMA and celiac axis (CA)	Death
Fujwara S., Sekine Y. [17]	2022	Case Report	Associated with thrombotic disease of the SMA, in a patient with a mediastinal tumor (Trousseau’s syndrome cannot be ruled out)	SMA	Death 27 days post-operation
D’Agostino V et al. [18]	2023	Case report	Pneumatosis without involvement of the portal mesenteric venous system	SMA	Death

) and twelve discussing the remaining arterial compartments, mostly about air in the arterial cerebral circulation (

Table 2. Summary of the previously published cases of air embolism in the systemic arterial compartments, except for SMA.

Author	Year	Type of Study	Cause of Air Embolism	Site of Air Embolism	Prognosis
Bidari A et Mohamadnejad M [19]	2002	Letter to editor	Pleurodesis	Cerebral arterial gas embolism; concurrent acute coronary syndrome	Hemiplegic and aphasic
Kantarci F et al. [20]	2004	Case report	Clostridial gas gangrene, in a patient with myelodysplastic syndrome and thrombosis of bilateral tibial arteries	Left posterior tibial artery (diagnosis made by Doppler-US)	Lower extremity amputation
Tsai Ming-Ju et al. [21]	2010	Case report	Salmonella infection	Aorta	No sequels
Tulmac M. et al. [22]	2012	Case report	Aortic root angiography (accidental injection of massive air)	Cerebral vasculature (no images) and coronary arteries	No sequels (after hyperbaric chamber session)
Lynn A. et al. [23]	2013	Research letter	Postpartum eclampsia, in a patient with PRES and pituitary apoplexy	Right side internal carotid artery, anterior communicating artery, and pericallosal artery	No sequels
Surve R.M. et al. [24]	2013	Letter to editor	Stent-assisted coiling of internal carotid artery aneurism	Case 1: complete occlusion of internal carotid artery Case 2: anterior cerebral artery	Case 1: severe disability Case 2: no sequels
Pua U. et al. [25]	2017	Letter to editor	Multiple EndoAnchor application, during endograft fixation	In the left limb of the bifurcated stent	No symptoms (thanks to prompt free air aspiration)
Edler C. et al. [26]	2018	Case report	Human error: connection between the infusion system and inhalation tubing system, in a patient affected by pneumonia	Arterial vessels and venous vessels (diagnosis by postmortem CT)	Death (postmortem diagnosis)
Popa D. et al. [27]	2019	Case report and review	Esophagogastroduodenoscopy	Cerebral vessels	Left-sided hemineglect, left upper extremity without movement (after hyperbaric chamber sessions)
Chuang D.Y. et al. [28]	2019	Case report	Peripheral intravenous catheter (accidental injection)	Cerebral vasculature	Left homonymous hemianopsia and mild left upper extremity weakness
Dioscoridi L et al. [29]	2020	Case report	ERCP	Right coronary artery and ventricles	No sequels
Bapteste L. et al. [30]	2021	Case report	Lumbar spine surgery	Cerebral arterial gas embolism (no examination; the clinical picture evokes the diagnosis)	No symptoms (after hyperbaric chamber session)

). The research period extended from January 2002 to August 2024 without specific temporal limitations.

According to the literature, systemic arterial air embolism (SAAE) is a rare but life-threatening condition that can occur especially after trauma or after interventional procedures, such as coronary catheterization, atrial fibrillation repair, and CT-guided endovascular lung biopsy [31]. Other related conditions include extracorporeal membrane oxygenation (ECMO), barotrauma (due to alveolar wall injury) [32], and repair of the thoracic aorta (TEVAR) [14,32] and endovascular procedure [13,16].

A few cases of air embolism have been described after endoscopic retrograde cholangiopancreatography in the prone position, pneumobilia in patients with a patent foramen ovale may lead to air embolism [29], and during lumbar surgery in the prone position—favored by a gravitational gradient between the heart and the surgical site and by negative pressure in the epidural veins as a result of decompression of the abdomen [30].

Cases of arterial gas embolism have also been described as a complication of clostridial gas gangrene [20], sepsis with disseminated intravascular coagulation (DIC) [17], and postpartum eclampsia [23].

The etiology of gas embolism can be varied: air may enter directly from an arterial inlet or the systemic venous system into the arterial system via an intracardiac shunt (patent foramen ovale or atrial septal defect), or due to the presence of a pulmonary arteriovenous malformation, which may allow gas to bypass the pulmonary vascular filter. Air embolism due to communication between the right and left compartments is called “paradoxical air embolism” [32].

Although in our case, the air embolism was potentially iatrogenic, i.e., related to the recent arterial catheterization for the treatment of coronary thromboaspiration, it is necessary to consider the theory of Giulio et al. [15], which cannot be excluded; according to this theory, after vasoconstriction and intravenous fluid administration in patients in hypovolemic shock with thromboembolic occlusions, a kind of vacuum effect may occur, with air passing from the intestinal lumen to the arterial compartment.

Some authors, such as Fujwara et al. [17] and Numata et al. [12], consider the presence of air in the arterial compartment as a serious indication of intestinal necrosis, especially when associated with intestinal pneumatosis [18]. Khripun et al. [16] speculate instead that it could be caused by reperfusion injury.

According to current guidelines, intestinal revascularization is necessary in most patients with acute SMA occlusion. The only situation in which bowel resection without revascularization can save the patient’s life is in the case of a distal embolism with a widely open proximal artery [33].

Since there is no standardized approach for the endovascular treatment of thrombo-embolic disease in SMA, we report the proposal of Tual et al. (Figure 5), who suggest different revascularization techniques depending on which tract of SMA is involved, in particular stenting for the S1 tract, mechanical thrombectomy for the S2 tract, and pharmacological thrombolysis for the S3 tract [6].

In the treatment of arterial gas embolism, the only therapeutic approach to date has been to place the patient immediately in a right lateral decubitus position to trap the air component in the left ventricle in an anti-declivity position, thus preventing some gas emboli from reaching the circulation. In addition, high oxygenation, usually 100%, should be ensured via a non-rebreather mask or intubation if necessary, or ideally via hyperbaric oxygen chamber therapy [31,32].

In conclusion, we have described an extremely rare case of AMI, with typical associated CT images associated with gas in the arterial system, the cause of which is controversial.

4. Conclusions

AMI is a complex condition to suspect and diagnose, as it presents signs and symptoms overlapping with other conditions. Nevertheless, early diagnosis and subsequent prompt and appropriate treatment can change the prognosis of this condition.

CT with contrast administration is the gold standard for diagnosis, as it allows the identification of characteristic patterns, sometimes associated with unusual findings, that may be a consequence or isolated cause of this clinical condition.

The radiologist, therefore, playing a central role in the diagnosis of a time-dependent pathology, should be adequately trained in all the typical features of the phases of acute mesenteric ischemia to be able to interpret the images adequately, thus improving the patient’s outcome.