Mesenteric Ischemia

Mesenteric Ischemia: Overview

Alternative Names: Mesenteric Artery Ischemia, Acute Mesenteric Ischemia (AMI), Chronic Mesenteric Ischemia, Mesenteric Vascular Disease, Nonocclusive Mesenteric Ischemia (NOMI), Occlusive Mesenteric Arterial Ischemia (OMAI), Acute Mesenteric Arterial Embolism (AMAE), Acute Mesenteric Arterial Thrombosis (AMAT), Abdominal Angina, Ischemic Colitis

Mesenteric Ischemia occurs after a narrowing or blockage in the three major arteries that supply the small and large intestines.  It is a rare, serious, and often fatal condition involving an interruption of blood flow to the intestines, potentially causing intestinal damage and destruction (gangrene).  It can be acute (appearing suddenly) or chronic (developing gradually).

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Early diagnosis is essential yet uncommon, and treatment can be extremely difficult.  The primary symptom is abdominal pain that has no obvious cause.

Incidence; Causes and Development; Contributing Risk Factors

Acute mesenteric ischemia (AMI) affects about 5 per 100,000 people per year in the developed world; Chronic mesenteric ischemia affects about 1 per 100,000.  Most sufferers are over 60 years old, with males and females being affected about equally.

The intestines have a high blood flow requirement, normally receiving 20-25% of the heart's output, and are very sensitive to any decrease.  Decreased blood flow disrupts the mucosal barrier of the intestines, allowing the release of bacteria, toxins and other compounds into the bloodstream.  This in turn can result in systemic inflammatory response syndrome, septic shock, multisystem organ failure and, eventually, death.

There are four ways in which poor blood flow to the small intestine can occur: a moving blood clot becoming lodged in an artery; a new blood clot forming in an artery; a blood clot forming in the mesenteric vein; and insufficient blood flow due to low blood pressure or artery spasms.

Risk factors include atrial fibrillation, heart failure, chronic renal failure, being prone to forming blood clots, and previous myocardial infarction.  It is often seen in those with hardening of the arteries; it is more common in smokers and in people with high blood pressure or high blood cholesterol levels.  Chronic disease is a risk factor for acute disease.

Signs and Symptoms

Symptoms are initially nonspecific, which often delays diagnosis and treatment until the disease is advanced.  The most important finding is moderate to severe pain that, upon examination, has no obvious cause.  The pain is diffuse, nonlocalized, and constant.

Acute Mesenteric Ischemia often presents with sudden and severe abdominal pain.  Signs and symptoms of chronic disease develop more slowly and include abdominal pain after eating, abdominal distention, unintentional weight loss, vomiting, diarrhea, gastrointestinal bleeding, and loss of appetite.

Symptoms can be divided into 3 progressive stages:

  1. The hyper active stage, where the main symptoms are severe abdominal pain and bloody stools.  The abdomen remains soft, with little or no tenderness.  A slightly higher than normal pulse rate may be observed.  Many patients recover spontaneously and do not progress past this phase.
  2. The paralytic stage may follow if ischemia continues: abdominal pain becomes more widespread, the belly becomes more tender to the touch, and bowel motility decreases, resulting in abdominal bloating, constipation, no further bloody stools, and an absence of bowel sounds.
  3. The shock stage may follow as the bowel becomes gangrenous and fluids begin to leak through the damaged intestinal lining.  Rectal bleeding and signs of sepsis may develop: shock, rapid heart rate, rapid breathing, metabolic acidosis with dehydration, low blood pressure, fever, and confusion.  Patients who reach this stage are generally critically ill and need intensive care.

A study of 58 patients showed the following prevalence of symptoms:

  • abdominal pain occurred in 55 patients (95%) and lasted an average of 24 hours.  The other 3 patients experienced shock and metabolic acidosis.
  • white blood cell count over 10.5 – 98%
  • lactic acid elevated – 91%
  • nausea – 44% (other surveys have found nausea and vomiting in 75% of affected patients)
  • vomiting – 35%
  • diarrhea – 35%
  • heart rate over 100 – 33%
  • blood from the rectum – 16%
  • constipation – 7%

Diagnosis and Tests

It is difficult to diagnose mesenteric ischemia early.  It must be differentiated from ischemic colitis (which often resolves on its own) and from the life-threatening condition of acute mesenteric ischemia.  The preferred method of diagnosis is angiography, with computer tomography (CT) being the second choice.  X-rays are generally not useful for diagnosis.

If not properly and rapidly treated, the outcome is usually death.  Therefore, AMI should be considered as a possible diagnosis in any patient with abdominal pain disproportionate to physical findings, gut emptying in the form of vomiting or diarrhea, and age older than 60 years.

Treatment and Prevention

Treatment of acute mesenteric ischemia (a medical emergency) may include placing a stent in the artery, or medications to break down the clot and widen the mesenteric arteries (vasodilators).  Conventional surgery may also be required in order to remove or bypass the obstruction, and to remove any section of the intestine that may have died.

In cases of chronic disease surgery to remove the blockage and reconnect the arteries to the aorta, or bypass surgery is usually the treatment of choice.  Those with vein thrombosis may initially be treated with anticoagulant medications such as heparin or warfarin, with surgery being used if they do not improve.

After successful treatment it is important to make lifestyle changes (such as a healthy diet and exercise) to prevent hardening of the arteries from getting worse.

Prognosis

In cases of mesenteric artery ischemia, prognosis is especially poor if the patient is not treated quickly.  Even with treatment the risk of death is 30-90%, depending on the stage at which treatment is started.

Signs, symptoms & indicators of Mesenteric Ischemia:

Symptoms - Abdomen

Meal-related pain for 1-4 weeks or meal-related pain for under a week

Because total blood flow to the intestine can vary from 25% when fasting to 35% after eating, symptoms are more prevalent after eating.

Meal-induced pain for 1-4 weeks or meal-induced pain for under a week

Because total blood flow to the intestine can vary from 25% when fasting to 35% after eating, symptoms are more prevalent after eating.

Counter-indicators

Symptoms - Bowel Movements

Symptoms - Gas-Int - General

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Conditions that suggest Mesenteric Ischemia:

Digestion

Mesenteric Ischemia can lead to:

Digestion

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