This article concerns ischemia of the small bowel. See ischemic colitis

Ischemic colitis

Ischemic colitis is a medical condition in which inflammation and injury of the large intestine result from inadequate blood supply. Although uncommon in the general population, ischemic colitis occurs with greater frequency in the elderly, and is the most common form of bowel ischemia...

 for ischemia of the large bowel

Mesenteric ischemia (or Mesenteric ischaemia - British English) is a medical condition in which inflammation and injury of the small intestine result from inadequate blood supply. Causes of the reduced blood flow can include changes in the systemic circulation (e.g. low blood pressure

Hypotension

In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...

) or local factors such as constriction of blood vessels

Vasoconstriction

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...

 or a blood clot. It is more common in the elderly.

Signs and symptoms

Three progressive phases of ischemic colitis have been described:

• A hyper active occurs first, in which the primary symptoms are severe abdominal pain and the passage of bloody stools. Many patients get better and do not progress beyond this phase.

• A paralytic phase can follow if ischemia continues; in this phase, the abdominal pain becomes more widespread, the belly becomes more tender to the touch, and bowel motility
  Peristalsis
  Peristalsis is a radially symmetrical contraction and relaxation of muscles which propagates in a wave down the muscular tube, in an anterograde fashion. In humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract. Earthworms use a similar...
  
   decreases, resulting in abdominal bloating, no further bloody stools, and absent bowel sounds on exam.

• Finally, a shock phase can develop as fluids start to leak through the damaged colon lining. This can result in shock and metabolic acidosis
  Metabolic acidosis
  In medicine, metabolic acidosis is a condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low due to increased production of hydrogen by the body or the...
  
   with dehydration
  Dehydration
  In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
  
  , low blood pressure
  Hypotension
  In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
  
  , rapid heart rate
  Tachycardia
  Tachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
  
  , and confusion. Patients who progress to this phase are often critically ill and require intensive care.

Clinical findings

Symptoms of mesenteric ischemia vary and can be acute (especially if embolic), subacute, or chronic.

Case series report prevalence of clinical findings and provide the best available, yet biased, estimate of the sensitivity of clinical findings. In a series of 58 patients with mesenteric ischemia due to mixed causes:

• abdominal pain
  Abdominal pain
  Abdominal pain can be one of the symptoms associated with transient disorders or serious disease. Making a definitive diagnosis of the cause of abdominal pain can be difficult, because many diseases can result in this symptom. Abdominal pain is a common problem...
  
   was present in 95% (median of 24 hours duration). The other three patients presented with shock and metabolic acidosis
  Metabolic acidosis
  In medicine, metabolic acidosis is a condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low due to increased production of hydrogen by the body or the...
  
  .
• nausea
  Nausea
  Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
  
   in 44%
• vomiting
  Vomiting
  Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
  
   in 35%
• diarrhea
  Diarrhea
  Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
  
   in 35%
• heart rate
  Heart rate
  Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
  
   > 100 in 33%
• 'blood per rectum
  Rectal bleeding
  Rectal bleeding can refer to:* Lower gastrointestinal bleeding* Hematochezia* Fecal occult blood* Melena...
  
  ' in 16% (not stated if this number also included occult blood - presumably not)
• constipation
  Constipation
  Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...
  
   7%

Diagnostic heuristics

In the absence of adequate quantitative studies to guide diagnosis, various heuristics help guide diagnosis:

• Mesenteric ischemia "should be suspected when individuals, especially those at high risk for acute mesenteric ischemia, develop severe and persisting abdominal pain that is disproportionate to their abdominal findings"
• Regarding mesenteric arterial thrombosis or embolism: "...early symptoms are present and are relative mild in 50% of cases for three to four days before medical attention is sought".
• Regarding mesenteric arterial thrombosis or embolism: "Any patient with an arrhythmia such as atrial fibrillation who complains of abdominal pain is hghly suspected of having embolization to the superior mesenteric artery until proved otherwise".
• Regarding nonocclusive intestinal ischemia: "Any patient who takes digitalis and diuretics and who complains of abdominal pain must be considered to have nonocclusive ischemia until proved otherwise".

Diagnosis

It is difficult to diagnose mesenteric ischemia early. One must also differentiate ischemic colitis

Ischemic colitis

Ischemic colitis is a medical condition in which inflammation and injury of the large intestine result from inadequate blood supply. Although uncommon in the general population, ischemic colitis occurs with greater frequency in the elderly, and is the most common form of bowel ischemia...

, which often resolves on its own, from the more immediately life-threatening condition of acute mesenteric ischemia of the small bowel.

Blood tests

In a series of 58 patients with mesenteric ischemia due to mixed causes:

• White blood cell count >10.5 in 98% (probably an overestimate as only tested in 81% of patients)
• Lactic acid
  Lactic acid
  Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
  
   elevated 91% (probably an overestimate as only tested in 57% of patients)

Devices for diagnosis during endoscopy

A number of devices have been used to assess the sufficiency of oxygen delivery to the colon. The earliest devices were based on tonometry, and required time to equilibrate and estimate the pHi, roughly an estimate of local CO2 levels. The first device approved by the U.S. FDA (in 2004) used visible light spectroscopy to analyze capillary oxygen levels. Use during Aortic Aneurysm repair detected when colon oxygen levels fell below sustainable levels, allowing real-time repair. In several studies, specificity has been 83% for chronic mesenteric ischemia and 90% or higher for acute colonic ischemia, with a sensitivity of 71%-92%. This device must be placed using endoscopy, however.,,

Computed tomography

Computed tomography

Computed tomography

X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

 (CT scan) is often used. The accuracy of the CT scan

Computed tomography

X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

 depends on whether a small bowel obstruction (SBO) is present .

SBO absent

• prevalence of mesenteric ischemia 23%
• sensitivity 64%
• specificity 92%
• positive predictive value
  Positive predictive value
  In statistics and diagnostic testing, the positive predictive value, or precision rate is the proportion of subjects with positive test results who are correctly diagnosed. It is a critical measure of the performance of a diagnostic method, as it reflects the probability that a positive test...
  
   (at prevalence of 23%) 79%
• negative predictive value
  Negative predictive value
  In statistics and diagnostic testing, the negative predictive value is a summary statistic used to describe the performance of a diagnostic testing procedure. It is defined as the proportion of subjects with a negative test result who are correctly diagnosed. A high NPV means that when the test...
  
   (at prevalence of 23%) 95%

SBO present

• prevalence of mesenteric ischemia 62%
• sensitivity 83%
• specificity 93%
• positive predictive value
  Positive predictive value
  In statistics and diagnostic testing, the positive predictive value, or precision rate is the proportion of subjects with positive test results who are correctly diagnosed. It is a critical measure of the performance of a diagnostic method, as it reflects the probability that a positive test...
  
   (at prevalence of 62%) 93%
• negative predictive value
  Negative predictive value
  In statistics and diagnostic testing, the negative predictive value is a summary statistic used to describe the performance of a diagnostic testing procedure. It is defined as the proportion of subjects with a negative test result who are correctly diagnosed. A high NPV means that when the test...
  
   (at prevalence of 62%) 61%

Findings on CT scan

Computed tomography

X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

include:

• Mesenteric edema
• Bowel dilatation
• Bowel wall thickening
• Intramural gas
• Mesenteric stranding

Treatment

"Surgical revascularisation remains the treatment of choice for mesenteric ischaemia, but thrombolytic medical treatment and vascular interventional radiological techniques have a growing role" .

Prognosis

The prognosis depends on prompt diagnosis (less than 12–24 hours and before gangrene) and the underlying cause:

• venous thrombosis - 32% mortality
• arterial embolism - 54% mortality
• arterial thrombosis - 77% mortality
• non-occlusive ischemia - 73% mortality