Acute Mesenteric Ischemia

by Rabind Antony Charles

Case Presentation

A 75-year-old woman presents to your Emergency Department (ED) with diffuse abdominal pain for the past day, associated with diarrhea and vomiting. She says the pain is increasingly worse and has failed to respond to paracetamol and charcoal tablets. She has a history of hypertension, hyperlipidemia, and atrial fibrillation. She has no history of laparotomy. She is alert and oriented. However, she is in distress because of her abdominal pain. The pain score is 9 out of 10. Blood pressure: 96 over 56 mmHg, pulse rate: 125 (irregularly, irregular), respiratory rate 20, pulse oximetry: 98% on room air, tympanic temperature: 37.5 degrees Celsius. Heart sounds: (irregular) S1S2 positive. Lungs sounds are bilateral equal and clear. Abdominal exam reveals diffuse tenderness; it is worse in periumbilical region, no guarding, bowel sounds are sluggish. No scars or hernias noted. Per rectal exam: brown stool.

What do you think about patient’s ECG?

Mesenteric Ischemia – Introduction

Acute mesenteric ischemia is a life-threatening cause of acute abdominal pain which occurs predominantly in patients over 50 years old with the underlying cardiovascular disease. It is caused by inadequate flow through the mesenteric vessels resulting in bowel ischemia and eventually gangrene of the bowel wall. Mortality rates can be between 60-80% especially in patients with greater than a 24-hour delay in diagnosis or presentation. This underscores the importance of early detection in the ED, and the need for aggressive management to reduce morbidity and mortality. Surgical intervention in 6 hours of symptoms increases survival rate.

Mesenteric artery embolism is responsible for 50% of patients. Symptoms are sudden onset of abdominal pain with bloody diarrhoea if infarct develops. Arrhythmias (e.g., Atrial fibrillation), valvular disorders and recent myocardial infarction are the predisposing factors for embolism.

Mesenteric artery thrombosis is around 25% of the patients.
Patients are generally shown atherosclerotic disease symptoms.
“Abdominal angina” for preceding months, which is a pain on eating with loss of weight, then sudden severe pain episodes.

In 20% of the reason is non-occlusive mesenteric ischemia. Hypotension, Congestive Heart failure, dialysis, use of vasoconstrictors or digoxin are predisposing factors. This situation happens typically intubated, sick ICU patients on vasopressors who deteriorate with bloody diarrhea and worsening hypotension.

If the patient has hypercoagulable states or his story of prior thromboembolic events, mesenteric venous thrombosis should be considered (5% of the patients). Patients represent with nonspecific abdominal pain with diarrhea 1-2 weeks after the event which may resolve spontaneously.

History Taking and Physical Examination Hints

This is a difficult condition to diagnose, especially in the early stages. However, it should be considered in those over 50 years old with severe abdominal pain, and predisposing factors for the condition.

In the early stages, patients may present with severe poorly localized abdominal pain, nausea, vomiting, and diarrhea with no signs of peritonism. These symptoms may mislead physicians into assuming the patients are suffering from gastroenteritis.

One of the key features to look out for is pain that is “out of proportion” to the abdominal findings. This is due to visceral ischemia with sparing of the parietal peritoneum in the initial stages. Peritonitis is a late finding and points towards severe bowel ischemia and necrosis. At this stage, there may be abdominal distension associated with reduced bowel sounds.
Mesenteric ischemia also can be more subacute in its presentation with the insidious onset of less severe and vague abdominal pain, abdominal distension, and occult gastrointestinal bleeding.

Differential Diagnoses

Depending on the clinical presentation, the differential diagnoses can be quite broad and include the following:

Acute gastroenteritis
Acute cholecystitis
Acute pancreatitis
Peptic ulcer disease
Bowel perforation
Diverticulitis
Bowel obstruction
Ureteric calculi

Emergency Diagnostic Tests and Interpretation

Laboratory Tests

There are “no” sufficiently sensitive or specific serum markers to identify acute mesenteric ischemia.

Complete Blood Cell Count: may show haemoconcentration and leukocytosis ( WBC count > 15,000/mm3) – lacks specificity.
Arterial/Venous blood gas analysis: metabolic acidosis is seen late in the disease. Presence of metabolic acidosis which cannot otherwise be explained should prompt the clinician to suspect mesenteric ischemia in the appropriate clinical context.
Serum lactate: nearly 100% sensitive when bowel infarction is present but lacks specificity and is not often increased without infarction.
Serum amylase may be moderately elevated in more than half of the cases (lacks specificity).

Imaging Modalities

Erect Chest x-ray/Abdominal x-ray series used mainly to exclude other causes of abdominal pain or look for complications of acute mesenteric ischemia (e.g., free gas/bowel obstruction). They are often normal in the early stages of acute mesenteric ischemia. However, there are some early and late findings in the X-rays. Early findings are adynamic ileus, distended air-filled bowel loops and bowel wall thickening from submucosal edema or hemorrhage. Pneumatosis of the bowel wall and gas in the portal venous system strongly suggest bowel infarction as late findings.

Multi-detector CT angiography is the primary imaging modality to diagnose acute mesenteric ischemia in the ED. The recent meta-analysis shows a sensitivity of 82.8- 97.6% and specificity of 91.2-98.2 when compared to conventional angiography, which is still considered the gold standard but is rarely available in ED.

The CT image shows bowel wall thickness.

The CT angiogram may show edema of the bowel wall and mesentery, abnormal gas patterns, intramural gas, ascites and occasionally direct evidence of mesenteric venous thrombosis. It will also determine other causes for the abdominal pain. If the CT is non-diagnostic and clinical suspicion for acute mesenteric ischemia remains high, there may be a need for angiography or diagnostic laparotomy depending on institutional practice.

Ultrasound has a limited role in the diagnosis of acute mesenteric ischemia. It is more useful for ruling out other causes of abdominal pain, e.g., cholecystitis, acute abdominal aneurysm rupture, ureteric colic.

Emergency Treatment Options

Initial Stabilization and Aggressive Resuscitation

Evaluation of patients with ABC approach gives the physician a chance to recognize immediate life-threatening problems. The most of the patients require supplemental oxygen. But, consider securing airway if needed. Correction of hypovolemia and hypotension (secondary to third space loss and/or bleeding) with normal saline/crystalloids is very important. Because most of the patients have multiple comorbidities, e.g., CHF; there may be a role for invasive hemodynamic monitoring with arterial lines, central venous pressure monitoring. IVC assessment with bedside Ultrasound can guide the fluid resuscitation before invasive procedures (RUSH protocol).

A quick tutorial on IVC measurement with ultrasound.

The ultrasound video shows collapsible and non-collapsible IVC. If the IVC collapse, this means the patient may benefit from fluid resuscitation.

If needed, correct any arrhythmias or CHF which may have contributed to the bowel hypoperfusion. Because one of the predisposing factors is vasoactive agents, discontinue these medications. If pressors are required to support the patient’s blood pressure, it is preferable to avoid alpha agonists. In this circumstances, use inotropes at the lowest possible dose. Start broad-spectrum IV antibiotics early, because of the high risk of bacterial translocation across the bowel wall. Patients should not receive anything orally and nasogastric tube placement to decompress stomach and bowel is often necessary. Correct any electrolyte abnormalities and acidosis.

Urgent surgical consultation should be obtained in the ED as this is a time-sensitive condition. Delays to definitive treatment will result in increased morbidity and mortality. It is best to get a surgical consult when suspicion is high for acute mesenteric ischemia even before a CT angiogram has been done.

Specific Treatment

In general, the definitive treatment of acute mesenteric ischemia depends on the underlying etiology and the presence or absence of necrotic bowel signs. This ultimately is decided by the surgeons and is one of the reasons why it is extremely important to get an urgent surgical consult when confronted with these patients. In the presence of necrotic bowel/peritonitis, bowel resection will need to be done regardless of which of the four types of the acute mesenteric ischaemic bowel.

In addition, there are some other specific options. Mesenteric artery embolism may benefit prom embolectomy then distal bypass graft. Mesenteric artery thrombosis needs bypass graft or stenting. Nonocclusive mesenteric ischemia requires to remove the underlying stimulus and correction of the underlying medical condition. Occasionally direct transcatheter papaverine (vasodilatory) infusion will restore normal blood flow. Mesenteric venous thrombosis showing mild ischemia may be treated with anticoagulation.

Disposition Decisions

These patients are critically ill with potentially high mortality rates, and as such, they should be admitted and managed in intensive care after surgery.

The Conclusion of Case

This patient was brought to the resuscitation area of the ED and was put on cardiac and blood pressure monitors and pulse oximetry. After ascertaining that her airway was intact, and providing supplemental oxygen with intranasal oxygen, 2 large bore IV cannulas were established and one liter of normal saline was started, with care taken not to tip her into fluid overload by serial assessment of IVC collapsibility with bedside ultrasound. CBC, renal panel, VBG, and serum lactate, group and crossmatch, and coagulation profile were sent off. Her leukocytes were 12,000 and serum lactate was elevated while the rest of the results were unremarkable. ECG showed atrial fibrillation (see picture given under the case presentation)

A bedside ultrasound excluded other causes of abdominal pain (e.g., ruptured abdominal aortic aneurysm, acute cholecystitis). Assessment of IVC collapsibility and cardiac ejection fraction gave the clues on aggressive fluid resuscitation. An NG tube was inserted and broad-spectrum IV antibiotics (ceftriaxone and metronidazole) were given. Portable CXR and AXR series were unremarkable. Based on her presenting complaint, a high suspicion for acute mesenteric ischemia (possible acute mesenteric embolism- due to her underlying atrial fibrillation) was entertained and urgent surgical consult was sought. A multidetector CT angiogram showed thickened small bowel wall, dilated bowel loops, and superior mesenteric artery embolism. She was rushed to the operation theatre for exploratory laparotomy as her abdomen was noted to be more tender and had some guarding.

As a summary, the role of the ED physician is to

resuscitate the patient as needed,
make an early diagnosis based on clinical suspicion,
understand the limitations of laboratory tests in ruling out acute mesenteric ischemia,
give priority to aggressively resuscitation and
get urgent surgical involvement

References and Further Reading

O’Keefe KP and Sanson TG. Mesenteric ischemia. In: Adams JG, et al. Emergency Medicine, 2008, p. 331.
Lewiss RE, Egan DJ, Shreves A. “Vascular Abdominal Emergencies” Emerg Med Clin N Am 29 (2011) 253–272.
Wadman M, Syk I, Elmsta° hl S. Survival after operations for ischaemic bowel disease. Eur J Surg 2000; 166(11): 872–7.
Disorders of the Small Intestine. Torrey, SP, Henneman, P. Rosen’s Emergency Medicine 7th edition.
Cudnik, M et al. The Diagnosis of Acute Mesenteric Ischemia: A Systematic Review and Meta-analysis. Academic Emergency Medicine, November 2013, Vol. 20, No. 11
Menke J. Diagnostic accuracy of multidetector CT in acute mesenteric ischemia: systematic review and meta-analysis. Radiology 2010;256(1):93-101.
Oldenberg WA . Lau LL, Rodenberg TJ, et al Acute mesenteric ischaemia: a clinical review. Arch Intern Med 2004; 164: 1054-62
emDOCs.net – Emergency Medicine EducationMesenteric …. http://www.emdocs.net/mesenteric-ischemia-power-review/