Acute Mesenteric Ischemia - Causes, Symptoms, Diagnosis, and Treatment

Introduction

Acute mesenteric ischemia is a condition that occurs due to a sudden incline in the blood flow in the mesenteric vessels. If the condition is not diagnosed on time and treatment is not started, there is necrosis of the small and large intestines seen, which further leads to sepsis and death. Acute mesenteric ischemia is a rapid progression condition that is difficult to diagnose and thus becomes life-threatening. Diagnosing acute mesenteric ischemia is difficult because the symptoms are not very specific. The mortality rate of acute mesenteric ischemia ranges from 60 to 80 percent. Acute mesenteric ischemia is differentiated as occlusive mesenteric ischemia and nonocclusive mesenteric ischemia.

What Are the Types of Acute Mesenteric Ischemia?

Acute mesenteric ischemia is divided into:

1. Occlusive mesenteric ischemia, is further divided into:

• Acute thromboembolism.
• Acute thrombosis.

2. Nonocclusive mesenteric ischemia.

What Are the Causes of Acute Mesenteric Ischemia?

The underlying conditions behind acute mesenteric ischemia include cardiovascular diseases such as congestive heart failure, atrial fibrillation, and myocardial infarction. Other causes are cardiac emboli, peripheral arterial emboli, or atheromatous plaque, which gets ruptured or dislodged after surgery.

Causes of Occlusive Acute Mesenteric Ischemia:

The causes include atheromatous vascular diseases such as

1. Atherosclerosis: Accumulating plaque from fats, cholesterol, and other substances in the artery's walls.

2. Aortic Dissection: Tear of tissue in the inner lining of the main artery aorta.

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3. Aortic Aneurysm: A large bulge in the aorta resembles a balloon and can rupture or dissect.

Other causes of occlusive mesenteric ischemia include decreased cardiac output, which can occur due to secondary causes such as myocardial infarction, dehydration, and congestive heart failure.

Causes of Nonocclusive Mesenteric Ischemia:

It is seen in critically ill patients with several comorbidities and is hemodynamically unstable.

The causes include:

1. Drugs such as vasopressors and ergotamines reduce blood flow.

2. Patients who underwent surgery such as cardiac or abdominal surgery recently.

3. Decreased blood pressure due to severe conditions such as sepsis, congestive heart failure, myocardial infarction, or renal diseases.

What Are the Symptoms Seen in Acute Mesenteric Ischemia?

• Abdominal pain is the typical symptom of acute mesenteric ischemia, which generally does not resemble the physical examination findings.

• In cases of embolic thrombosis, there is rapid emptying of the bowel, which is violent, followed by severe abdominal pain.

• Tenderness is felt on palpation in cases where complete bowel is involved, which further starts necrotizing.

• The symptoms of embolism thrombosis gradually progress to necrosis and ischemia due to limited collateral blood flow.

• Patients also complain about other symptoms such as distension, diarrhea, bloody stool, and postprandial pain.

• Nonocclusive mesenteric ischemia progresses very slowly and is not localized to a place. Its consistency and severity also vary.

• Patients suffering from nonocclusive mesenteric ischemia are critically ill with conditions such as cardiac disease, septic shock, respiratory failure, and decreased blood pressure.

How to Diagnose Acute Mesenteric Ischemia?

• Computed tomography angiography is the preferred imaging method in all cases of acute mesenteric ischemia. Acute mesenteric ischemia has a sensitivity of around 94 percent to computed tomography angiography.

• Catheter-directed angiography was also performed earlier, but it was gradually outdated as the surgical method is a stressful technique in cases of already critical patients.

• Plain abdominal radiographs, magnetic resonance angiography, and ultrasonography have very narrow indications in cases of acute mesenteric ischemia.

• The laboratory values and biomarkers for acute mesenteric ischemia do not show any diagnostic traces of the disease.

How to Treat Acute Mesenteric Ischemia?

• The initial treatment for acute mesenteric ischemia is to correct the electrolyte imbalances and fluid resuscitation. It is important to avoid vasopressors or alpha-adrenergic agents, which can lead to vasospasm.

• The initial surgical approach is necessary to evaluate the level of ischemia and necrosis. Before the surgery, the administration of broad-spectrum antibiotics is important to prevent abdominal sepsis if the necrotic bowel gets resected.

• Revascularization (regeneration of blood supply) is the primary goal of surgeries, followed by the removal of necrosed bowel segments.

• After the revascularization, it is necessary to evaluate the bowel for a few days to check for pulses with the help of a continuous wave doppler, peristalsis movement, and the region's normal color.

• In cases of occlusive mesenteric ischemia, the surgical intervention depends upon the type and location of vessel occlusion and whether it is open or endovascular. Generally, bowel resection is carried out in first exploratory surgery in almost 31 percent of cases, but in approximately 53 percent of cases, second-outlook surgeries are also performed. Second-look surgeries are performed due to difficulty in assessing the extent of bowel necrosis.

• In cases of nonocclusive mesenteric ischemia, the treatment is focused on reversing the underlying cause of the ischemia. Catheter-directed papaverine, a phosphodiesterase inhibitor delivered by a side-hole or thrombolysis catheter, is also an interventional option.

Which Diseases Show Symptoms Similar to Acute Mesenteric Ischemia?

The diseases which cause acute abdominal pain are differential diagnostic diseases for acute mesenteric ischemia, such as:

• Diabetic Ketoacidosis: Production of high levels of ketones in complicated diabetes conditions. The symptoms are nausea, vomiting, and stomach pain.

• Bowel Obstruction: Blockage in the small or large intestine with bowel obstruction. It leads to acute abdominal pain and cramps.

• Ruptured Abdominal Aortic Aneurysm: Tear off in one or more walls of the aorta leading to internal bleeding. It causes acute stomach pain, and the condition is fatal.

• Acute Colitis: Inflammation and soreness of the gastrointestinal tract. It leads to nausea, vomiting, and abdominal pain.

• Gastrointestinal Perforation: Leakage from any part of the gastrointestinal tract leads to infection and necrosis. This can be a serious condition.

• Malignancies: Any late-stage cancerous lesion can lead to acute stomach pain and abdominal discomfort, similar to acute mesenteric ischemia.

Conclusion

Acute mesenteric ischemia is a serious condition in which blood flow is restricted to a part of the bowel, which can gradually diffuse and affect the entire bowel. It leads to necrosis, sepsis of the abdomen, and ultimately death if not diagnosed and treated on time. The most common symptom of the disease is acute stomach pain. Treating the condition with surgical intervention is important by resecting the area of infection and necrosis.