Introduction

Mesenteric ischemia is considered a vascular emergency, predominantly affecting elderly patients.^1,2 The disease carries a mortality rate ranging from 50-70%, where it can be as high as 90%.³ Early prevention and risk reduction are essential for managing this often fatal condition.¹ In the early 1990s, 2/3rds of patients with mesenteric ischemia died which led to the disease being labelled as a rare condition which inescapably leads to the death of a patient.⁴ However, this is mostly due to the difficulty of early detection.⁴ Speed and accuracy of diagnosis are essential in this disease, where treatment within the first 6 hours of the disease can reduce mortality to 10-20%.⁵ With more recent education of the disease, mortality rates have luckily been greatly reduced, However, mortality and incidence of this disease can be further reduced through focusing more on prevention strategies.⁵ 

This article will be discussing:

• What mesenteric ischemia is
  • The types of mesenteric ischemia
• The causes of mesenteric ischemia are:
  • Nonocclusive mesenteric ischemia
  • Mesenteric arterial embolism
  • Mesenteric arterial thrombosis
  • Mesenteric venous thrombosis
• Diagnosis of mesenteric ischemia
  • Imaging
  • Lab tests
• Treatments for mesenteric ischemia
• Risk factors for mesenteric ischemia
• Prevention of mesenteric ischemia

What is mesenteric ischemia?

Mesenteric ischemia occurs when the splanchnic blood flow is insufficient to meet the metabolic needs of the small intestine. After eating there is a large surge in blood flow from 10-20 minutes, depending on the size of the meal. The small intestine can only tolerate a 74% reduction of blood flow for around 12 hours, however, a complete occlusion can result in ischemia (tissue death) for around 6 hours. Mesenteric ischemia occurs within the mesenteric artery, which supplies blood to the abdominal aorta, celiac axis, superior mesenteric artery, and inferior mesenteric artery.⁶ The superior mesenteric artery is a single vessel, where its terminal zone is affected 85% of the time in mesenteric ischemia.¹  

Symptoms of mesenteric ischemia

Mesenteric ischemia can be seen to come on very rapidly, where it can initially be thought to be benign with only mild tenderness of the abdomen, however, an individual's condition will worsen rapidly to nausea, vomiting and diarrhoea.³ Initially, there is abdominal pain, followed by no pain as a result of nerve damage. This will be followed by mucosal ischemia and collapse of the membrane which will allow for bacteria to infiltrate, leading to peritonitis, ileus, sepsis and multiorgan failure.¹   

Types of mesenteric ischemia

Mesenteric ischemia can be subdivided into four types:³ 

• Nonocclusive mesenteric ischemia (NOMI)
• Acute thrombosis of mesenteric arteries
• Acute embolism of mesenteric arteries 
• Mesenteric venous thrombosis

What causes mesenteric ischemia?

There are four types of mesenteric ischemia which have different diagnostic criteria and treatment requirements.^3,4 

• Nonocclusive mesenteric ischemia:
  • This is seen in only 20% of cases, however mortality rates are from 90 to 50-70%
  • It is caused by vasoconstriction of splanchnic arteries
  • Risk factors from cardiac syndromes
  • Detection can be challenging
  • Treatment requires treatment of the underlying condition
• Arterial embolism:
  • Seen in 20-35% of cases
  • The mesenteric artery is specifically prone to embolisms due to its fast flow rate, large diameter of 3 -10cm and acute angle from the aorta
  • Can be at risk of mesenteric embolisms with:
    • Atrial fibrillation (rheumatic heart disease)
    • Left ventricle cardiomyopathies
    • Atherosclerosis
    • Ventricular aneurysm
    • Rheumatic heart disease
    • Lactogenic causes from catheterisation of the coronary or cerebral
• Mesenteric arterial thrombosis:
  • Occurs in 15-25% of individuals 
  • Individuals are at risk of mesenteric thrombosis with:
    • Peripheral vascular disease with atherosclerosis
    • Stenosis of SMA
    • Aneurysms
    • Aortic dissection
    • Systemic vasculitis
    • SMA dissection
    • Thrombophilia
• Mesenteric venous thrombosis (MVT):
  • Accounts for 5-10% of intestinal ischemia cases, where there is a thrombosis of the superior mesenteric venous system
  • Are at risk of mesenteric venous thrombosis with:
    • inherited thrombophilia
    • acquired thrombophilia
  • Treatment involves anticoagulation therapy or catheter-directed thrombolysis

Diagnosis of mesenteric ischemia

Efficient diagnosis is essential in treating mesenteric ischemia, where the following imaging can be used:^1,2,7

• CT angiography scan of the abdomen in both arterial and venous phases 
• Catheter angiography
• Abdominal ultrasonography 
• Magnetic resonance angiography 
• Mesenteric Doppler ultrasonography
• Endoscopy 

Lab tests

Health specialists will analyse your blood sample by looking for:⁷ 

• An increase in white blood cell count which could predict necrosis
• High lactate levels 

Treatment for mesenteric ischemia

Individuals suspected to have mesenteric ischemia may be given the following depending on the subtype of diagnosis:³

• Fluids
• Antibiotics
• Anticoagulants
• Operative intervention if there is peritonitis, intestinal gangrene, or central occlusion

Risk factors for mesenteric ischemia:

There are various risk factors associated with mesenteric ischemia, however, one of the largest risk factors has to do with age, where mesenteric ischemia occurs much more often in patients >70 years of age.³ Because mesenteric ischemia is caused by impairment of blood flow due to an underlying cause, a large variety of health conditions and lifestyle risk factors are associated with mesenteric ischemia.² These can include:

• Cardiovascular disease:
  • atherosclerotic disease
  • heart failure
  • atrial fibrillation
  • myocardial infarction
  • coronary heart disease
  • arterial hypertension
  • high cholesterol 
  • high blood pressure
  • hypercoagulation disorder 
• Prior embolic events
• Haemodialysis
• Recent abdominal or vascular surgery
• Peripheral artery disease
• Tobacco use 

Prevention of mesenteric ischemia

Prevention of mesenteric ischemia can be achieved through:

• Stopping smoking: this can cause damage to blood vessels which can further increase your risk of mesenteric ischemia
• Exercise: can keep your heart and circulatory system healthy
• Healthy diet: maintaining a diet low in fats and sodium can maintain blood pressure
• Taking medications: Make sure medications for high blood pressure or cholesterol can reduce risk factors of mesenteric ischemia
• Regular checkups: having regular checkups can ensure high blood pressure can be caught early and treated to prevent mesenteric ischemia

Summary

Overall mesenteric ischemia is a vascular emergency which primarily affects elderly individuals and has a relatively high mortality rate. Early prevention, rapid diagnosis and timely treatment are crucial to manage this life-threatening condition. Recent advancements in diagnosis through imagery and lab testing have greatly reduced mortality, however, a better understanding of risk factors and prevention can further reduce these rates. This can include addressing an underlying health condition like diabetes, adopting a healthier lifestyle and ensuring regular health checkups. Understanding this disease requires a combined effort from radiologists, vascular surgeons, and gastrointestinal surgeons. This disease is considered a disease of an ageing population, therefore as we start to live to older ages there is a great demand to enhance our understanding, prevention, diagnosis and treatment options for mesenteric ischemia to combat this disorder.