Edited By: David Gordon, MD
Durham, North Carolina
Mesenteric Ischemia Objectives
- Describe the classic presentation of mesenteric ischemia
- Describe the clinical presentation of mesenteric ischemia specific to each of the 4 different mechanisms of disease
- Explain the utility of laboratory testing in the diagnosis of mesenteric ischemia
- Discuss the role of different radiologic studies in the diagnosis of mesenteric ischemia
- List the findings of mesenteric ischemia that can be found on CT
- Discuss the treatment of mesenteric ischemia based on mechanism of disease
In spite of all our technological advances in medicine, mesenteric ischemia remains a difficult disease process to identify. Often patients will present with non-specific signs and symptoms leading physicians astray as they consider other abdominal pathologies. If the diagnosis is not considered early in the patient's presentation, the intestines will rapidly become gangrenous leading to multisystem organ failure, sepsis, and eventual death. It is no wonder that the morbidity and mortality rates for mesenteric ischemia still remain high today.
Luckily, mesenteric ischemia is not a common disease as it is only seen in 0.1% of hospital admissions. It predominately affects older patients with significant co-morbidities such as arrhythmia, atherosclerosis, congestive heart failure, and hypercoagulability. The main goal is to identify mesenteric ischemia early in undifferentiated abdominal pain patients so that rapid revascularization to the mesentery can be achieved preventing bowel infarction.
The classic presentation for mesenteric ischemia will be in a patient older than 50 years of age who presents with sudden onset of abdominal pain which may be associated with nausea, vomiting, and diarrhea.
The abdominal pain will initially be severe and diffuse without any localization. One of the distinctive findings in mesenteric ischemia is that of abdominal pain that is out of proportion to examination. The patient may be screaming in pain, but their abdomen is soft with no guarding or rebound. As the disease progresses and the bowel becomes infarcted, the patient will develop abdominal distension with guarding, rebound, and absence of bowel sounds. Heme-positive stools are also a late finding.
The aforementioned description is the classic presentation, often seen on standardized tests. To truly understand the real life presentations of mesenteric ischemia, the four different etiologies of this disease must be analyzed: mesentery artery embolus, mesentery artery thrombosis, mesenteric vein thrombosis, and non-occlusive ischemia.
Mesenteric Artery Embolus
This is the most common cause of mesenteric ischemia accounting for 40 to 50% of cases. The prognosis is poor with a 70% mortality rate. Onset of symptoms is sudden due to the acute nature of an embolus lodging in the artery with little time for collaterals to form. Patients with mesenteric artery embolus will present with the classic abdominal pain out of proportion to exam. Risk factors for mesenteric artery embolus include arrhythmias (atrial fibrillation being the most common), post-myocardial infarction with mural thrombi, valvular heart disease, and structural heart defects (such as right to left shunts).
The most common location of an embolus is in the superior mesenteric artery (SMA) due to the oblique angle of the SMA from the aorta. The embolus usually lodges distal to the origin of the middle colic artery, sparing the duodenum and proximal jejunum as compared to a mesenteric artery thrombosis which causes a more proximal blockage leading to extensive bowel ischemia.
Mesenteric Artery Thrombosis
Mesenteric artery thrombosis accounts for 25 to 30% of mesenteric ischemia cases and possibly carries the worst prognosis with a mortality of 90%. This high mortality is due to the thrombus usually being near the origin of the SMA causing an enormous amount of bowel necrosis. Most patients with a mesenteric artery thrombosis have a history of chronic mesenteric ischemia with vague and insidious symptoms such as weight loss, abdominal angina (abdominal pain after meals), diarrhea, and fear of food. Risk factors include systemic atherosclerosis and older age.
Mesenteric Vein Thrombosis (MVT)
MVT is the least common cause of mesenteric ischemia involving 10% of cases with a mortality of 20 to 50%. It occurs in a relatively younger patient population. Symptoms can occur acutely or occur over time depending on the pace at which the thrombus progresses. Accordingly, the abdominal pain onset and location can be variable as well, however, there is no postprandial abdominal pain or food fear as seen in mesenteric artery thrombosis. Patients may also have other accompanying symptoms such as vomiting and diarrhea. MVT risk factors include hypercoagulable states (Factor V Ledien, protein C deficiency, etc.), recent surgery, malignancy, and cirrhosis. In addition, up to 50% of patients will have a history of deep vein thrombosis.
Non-occlusive ischemia accounts for 20 to 30% of cases with mortality rates ranging from 50 to 90%. This type of mesenteric ischemia occurs in low flow states in absence of an arterial or venous occlusion. Any condition associated with decreased cardiac output can cause non-occlusive ischemia including cardiogenic shock, congestive heart failure, and arrhythmias. Sepsis, hypotensive states, and drugs inducing mesenteric vasoconstriction (Digoxin, Cocaine, Alpha-agonists, Beta-blockers) can also be causes. This disease process often develops during hospitalization in sick patients suffering from other illnesses so a high index of suspicion is required to diagnose it. Treatment involves targeting the underlying cause and correcting it.
|Mesenteric Ischemia Types||% of Cases||Mortality||Risk Factors|
|Mesenteric Artery Embolus||40-50%||70%||
|Mesenteric Artery Thrombosis||25-30%||90%||
|Mesenteric Vein Thrombosis||10%||20-50%||
|Non-Occlusive Mesenteric Ischemia||20-30%||50-90%||
Generally, labs by themselves are not helpful in making the diagnosis of mesenteric ischemia from other abdominal pathologies.
The white blood cell count is commonly elevated, but is a non-specific finding and a normal white count does not rule out the disease. Hemoconcentration, elevated amylase levels, and a metabolic acidosis may also be found in mesenteric ischemia, but again are non-specific findings.
An elevated lactate level is sensitive for mesenteric ischemia. However, the lactate is only elevated late in the disease course after bowel has infarcted and its specificity is low.
Plain films of the abdomen will typically be normal in the early course of the disease. An upright film should be a part of the abdominal x-ray series to help rule out free air. As the ischemia progresses, subtle signs such as thickening of bowel wall and distended loops of bowel can be seen, but like the labs are non-specific signs.
Pneumatosis of the intestinal wall can occasionally be seen on plain film, but is a late finding when bowel has become necrotic.
Angiography is the gold standard for mesenteric ischemia allowing for diagnosis and therapy. Lateral views allow for examination of the origins of the major vessels while AP views allow for visualization of distal mesenteric vessels. The site and type of occlusion can be identified via angiography.
Non-occlusive ischemia can also be identified via this modality. Medications such as papaverine and thrombolytics can also be infused during angiography (more details in the Treatment section).
The downsides of angiography are that it is an invasive and lengthy procedure and may not be readily available at all hospitals or all times of day.
Multidetector CT Angiography
CT angiography (CTA) is rapidly becoming an alternative to angiography. CTA is fast, less invasive than angiography, and readily available in most hospitals. In addition to the vascular findings of thrombus and emboli, CTA can also demonstrate more subtle signs of mesenteric ischemia such as circumferential thinking of the bowel wall, bowel dilatation, bowel wall attenuation, and mesenteric edema.
Other pathologies such as appendicitis and bowel obstruction, which may present with symptoms similar to mesenteric ischemia, can also be diagnosed and not missed. Unlike angiography, CTA cannot provide therapy, but can help triage patients towards those who can undergo angiography and those who should go to the operating room immediately. Patients requiring CTA need good renal function as IV contrast dye is used.
There are some problems with using ultrasound to diagnose mesenteric ischemia. A skilled ultrasonagrapher along with a radiologist who is trained in interpreting the images is required. Obese patients, copious bowel gas, and prior abdominal surgeries will limit the quality of the ultrasound images. Distal emboli are also difficult to see on ultrasound. Due to these reasons, ultrasound is not a first line study for diagnosis of mesenteric ischemia.
Magnetic Resonance Angiography (MRA)
MRA can help identify proximal occlusions, but it is limited as a diagnostic test by not being available at all hospitals and times of day and also being a lengthy test which could delay surgical intervention.
How do I make the diagnosis?
As an uncommon disease, the diagnosis of mesenteric ischemia hinges upon maintaining a high index of suspicion. Remembering the different clinical presentations and associated risk factors will help ensure appropriate consideration. Patients with a history of an arrhythmia and/or structural heart disease who present with the acute onset of severe abdominal pain that is out of proportion to exam should be suspected of having a mesenteric artery embolus. The triad of post-prandial pain, fear of food, and resultant weight loss in the setting of advanced age and vascular disease should raise concern for mesenteric artery thrombosis. Young patients with underlying risk factors for venous thromboembolic disease may have mesenteric venous thrombosis. Non-occlusive thrombosis should be entertained in patients with low flow states or in patients who have been exposed to drugs associated with mesenteric vasoconstriction.
A lactic acid level is an appropriate test to order when evaluating for mesenteric ischemia but may not be elevated until late in the disease course. CT angiography serves as a fast and widely available diagnostic imaging study that can confirm the diagnosis by direct visualization of clot within the vasculature and by detecting changes in the appearance of the bowel suggestive of ischemia.
Treatment must be initiated early in patients suspected of having mesenteric ischemia. Two large bore IV's with crystalloid fluids wide open are necessary in patients who are hypotensive. Continuous monitoring of vital signs is paramount and the insertion of a triple lumen for central venous pressure monitoring may be required to guide IV fluid treatment, especially in patients with a history of congestive heart failure. Broad spectrum antibiotics covering bowel flora should be started and any medications with vasoconstrictive properties should be stopped. If a thrombus is suspected, an anticoagulant such as heparin should be started to halt propagation of the thrombus. Heparin is good in that it can be shut off quickly if the patient is to go to the OR. If the patient is undergoing angiography, papaverine can be given during the procedure to increase blood flow to bowel that is not perfusing well by reducing mesenteric vasoconstriction.
The ultimate management of acute mesenteric ischemia is challenging and ever changing. Treatment can range from non-operative management with medications, intravascular thrombolytics, percutaneous angioplasty, operative revascularization, resection of bowel, or a combination of therapies. The treatment for each patient must be individualized depending on the patient's state of health, cause of ischemia, and resources that are available. Listed below are the treatments based on the four etiologies of mesenteric ischemia.
Mesenteric Artery Embolus
Thrombolytics can be directly infused into the artery containing the embolus during angiography. This is a good technique to use in non-operative candidates. The drawback is that bowel viability generally assessed during laporatomy cannot be done. In addition, contraindications to thrombolytics include recent surgery or GI bleed, recent stroke, and peritoneal signs indicating bowel infarction.
If operative management is decided, revascularization is done first so that any ischemic-looking bowel can recover with the return of blood flow. Once blood flow is reestablished, any bowel that remains infarcted and necrotic is then resected. Surgeons will do "second look" procedures 24-48 hours later if the viability of a section of bowel was in question during the first surgery.
Mesenteric Artery Thrombosis
In this etiology, heparin should be started as soon as the diagnosis is made and prior to surgery. The corrective operative measures for mesenteric artery thrombus are the same as for mesenteric artery embolus. For non-operative candidates, percutaneous transluminal angioplasty is done. In patients with chronic mesenteric ischemia and mesenteric artery thrombosis, there has been complete resolution of symptoms after intervention.
Mesenteric Vein Thrombosis
If there are signs of infarction, then operative care is required. Otherwise anticoagulants, thrombolytic therapy, or a combination of both is incorporated. These patients will generally require life-long anti-coagulation.
Non-occlusive Mesenteric Ischemia
The treatment is to correct the underlying cause of the low flow state to the bowel whether it be sepsis or decreased cardiac output. Papaverine can help treat the vasoconstriction of the vessels to the mesentery which will maximize blood flow. Patients who develop peritoneal signs must go to the OR.
All patients with mesenteric ischemia are admitted, generally to an intensive care unit for close monitoring due to the high mortality and ability for these patients to become sick rapidly. The surgeons can either be the admitting doctors or can be consultants with intensivists being the admitting doctors. Interventional radiology will need to be consulted if angiography is performed.
Pearls and Pitfalls
- Mesenteric ischemia must be considered early in a patient's course with aggressive management including the early use of CTA or angiography
- It is very important to know the risk factors and treatment modalities of the four different types of mesenteric ischemia: mesenteric artery embolus, mesenteric artery thrombosis, mesenteric vein thrombosis, and non-occlusive ischemia
- The signs and symptoms for mesenteric ischemia are vague with "pain out of proportion to exam" being the classic presentation
- Currently, there are no highly sensitive and specific lab tests for mesenteric ischemia
- Despite the new advances in medicine, the mortality for mesenteric ischemia remains very high
- Ofer A, Abadi S, Nitecki S, et al. Multidetector CT angiography in the evaluation of acute mesenteric ischemia. Eur Radiol 2009; 19: 24-30.
- Schermerhorn ML, Giles KA, Hamdan AD, et al. Mesenteric revascularization: managment and outcomes in the United States, 1988-2006. J Vasc Surg 2009; 50: 341-348.
- Acosta S, Ogren M, Sternby N, et al. Clinical implications for the management of acute thromboembolic occlusion of the superior mesenteric artery: autopsy findings in 213 patients. Ann Surg 2005; 241: 516-522.