Intestinal ischemia is the term used to describe the result of a variety of disorders that cause insufficient blood flow to the gastrointestinal tract. Such ischemic injuries can manifest with symptoms ranging from a mild bout of short-lived abdominal pain or diarrhea to bloody diarrhea or a more serious situation, such as gangrene that may require surgery and even end in death.
Intestinal ischemia can be a devastating disease, but there has been extraordinary progress over the past 50 years in our medical understanding of intestinal ischemia; a growing number of physicians now recognize and diagnose intestinal ischemia early, thereby improving outcomes for their patients. Current management of intestinal ischemia has evolved from simply managing the grave consequences after an acute event to more aggressive and proactive methods aimed toward recognizing and exploring early warning signs and preventing potentially catastrophic complications. With our current knowledge of the disease and the availability of modern diagnostic and therapeutic options, it is now possible to offer increasing comfort and reassurance that the intestines and the lives of many patients can be salvaged.
It is essential to emphasize that successful management of intestinal ischemia involves a partnership between patients and their physicians. Recognition of the early symptoms and risk factors for the disease by patients greatly enhances their physicians’ ability to offer a diagnosis and appropriate management.
In general terms, ischemia either can be localized to a relatively small part of the small intestine or colon, or it may be more widespread and involve significant portions of both.
The time course of the ischemic event also may vary and be acute (new), chronic (long-standing), or recurrent.
An ischemic problem may be caused by an interruption in blood passage through an artery (a blood vessel that brings blood to the intestines) or vein (a blood vessel that returns blood from the intestines to the heart). There are several ways in which arterial blood supply to the intestines can be restricted: an embolus (a migrating blood clot that can form a blockage), a thrombus (a stationary clot attached to the wall of a blood vessel that can prohibit blood passage), or a so-called non-occlusive state (spasm of a blood vessel, but without permanent obstruction, that restricts blood flow through an artery).
Venous problems also may result in intestinal ischemia, although less commonly than arterial causes. The most common cause of ischemia from venous obstruction is a thrombus which interferes with the return of blood flow from the intestines, produces intestinal congestion, and results in intestinal swelling, and occasionally bleeding.
The ultimate effects of reduction in intestinal blood flow vary. The milder forms of ischemic injury may involve several days of abdominal discomfort and altered bowel habits (e.g., diarrhea, bloody stool) or chronic low-grade cramping abdominal pain associated with eating (“intestinal angina”). The more severe cases may present with life-threatening gangrene and rupture of the intestines or bleeding, and may require hospitalization and surgery. In order to take full advantage of the advances made in the diagnosis and treatment of these disorders and to improve the chances of recovery, early diagnosis is essential. Individuals who experience the symptoms detailed below, particularly those persons who are identified at greatest risk for intestinal ischemia, should seek the attention of their physician immediately.
Intestinal ischemia exhibits a broad spectrum of presentations. There is no single set of symptoms which can fully predict the type of ischemic injury, its cause or its prognosis. There are, however, some generally recognized patterns of ischemic disease.
The most common form of ischemic injury to the intestines is colon ischemia. Colon ischemia usually manifests as sudden, mild-to-moderate left-sided lower abdominal pain with an urgent desire to defecate, and the passage, within 24 hours, of bright red or maroon blood mixed with the stool. Alternatively, some patients with colon ischemia manifest severe right-sided lower abdominal pain with minimal to no bleeding. The vast majority of patients with colon ischemia do well; a minority develops irreversible disease such as chronic ischemic colitis, stricture (narrowing) formation or gangrene. Patients who have colon ischemia that is confined to the right side of the colon have a worse prognosis with a greater need for surgery and a higher mortality rate than patients whose colon ischemia affects other parts of the colon, alone or in combination with right-sided involvement.
Most patients with an acute episode of small intestinal ischemia present with the sudden onset of severe abdominal pain. Early in the process, the abdomen is usually soft, flat, and not tender to touch. Most patients with small intestinal ischemia do not have diarrhea or rectal bleeding. Abdominal distention may be the first sign of a serious injury to the intestines. A sudden, forceful bowel movement associated with severe abdominal pain suggests an acute arterial occlusion caused by an embolus.
A more slowly developing course usually occurs when small intestinal ischemia is caused by an arterial obstruction from a thrombus. The obstruction is usually clinically silent but causes pain when blood flow is insufficient to permit the basic activities of the intestines, such as normal motility and digestion. The presence of abdominal pain specifically after meals in the weeks to months before an acute thrombosis is sometimes prelude to such an occurrence.
Patients with acute small intestinal ischemia resulting from a thrombus in a vein rather than an artery also experience abdominal pain. The pain is more variable and typically less severe than with arterial thrombosis; it may occur in a so-called “tumbleweed” type of recurring and remitting abdominal pain. Other symptoms may include nausea, vomiting, and diarrhea with or without blood. Here again, patients usually have already had more subtle symptoms prior to the sudden event. Many patients with a venous thrombus have been diagnosed with blood clots in the past or have a high risk of developing clots because of a familial clotting problem, or underlying conditions like cancer, inflammatory bowel disease (IBD), or lupus, or because they take medications that may promote clotting such as oral contraceptives.
The presence of non-occlusive acute small intestinal ischemia (from spasm of the blood vessels) may be overshadowed by the other illnesses a patient might have, such as heart failure, hypotension (low blood pressure), a heart attack, or cardiac arrhythmia (irregular heart beat). A patient in these settings may already be quite ill and abdominal pain may be absent. Unexplained abdominal distention or bleeding from the rectum may be the only signs of intestinal ischemia in these circumstances.
Chronic small intestinal ischemia (or “intestinal angina”) is typically associated with dull, cramping abdominal pain felt 10 to 30 minutes after eating and reaching its peak 1 to 3 hours after a meal. The pain can increase in severity to where the patient fears eating and therefore reduces the size of meals or eats less frequently and loses weight. Symptoms of this condition, in contrast to those of the other intestinal ischemic disorders, usually become progressively more severe over an extended period of time, without resulting in a severe crisis until late in the picture.
The gastrointestinal tract forms a complex system of tubing that extends more than 30 feet from the mouth to the anus. The intestines perform a variety of essential tasks, most important of which is the absorption of nutrients from food and the concentration and passage of waste from the body in the form of stool. These activities require oxygen and other vital substances that are delivered to and recycled from the intestines by an extensive and often redundant network of blood vessels called arteries and veins.
When intestinal blood flow is diminished to a point that there is a shortage of the resources the intestines require for their sustenance, intestinal ischemia results; this shortage prevents the intestines from functioning properly. The type and prognosis of ischemic injury can vary greatly and depends on the cause of the injury, the blood vessel(s) involved, the underlying medical condition of the patient, and the swiftness with which the problem is brought to medical attention for diagnosis and treatment.
Identification of intestinal ischemia often involves a high level of suspicion.
Generally, those who are most susceptible are individuals older than 50 years of age, particularly those who suffer from diseases such as heart failure and irregularities of cardiac rhythm, and those who have had a heart attack or stroke. Various medications used to treat migraine headaches and constrict blood vessels or oral contraceptives also may lead to intestinal ischemia. Additionally, individuals predisposed to developing blood clots, also called a venous thrombosis, are more likely to develop intestinal ischemia. This problem can affect young people as well as older individuals and is most often seen in those who have suffered a recent traumatic leg injury and individuals who have been immobile for long periods of time. Others at increased risk for blood clots are those who have a predisposing genetic disorder, IBD, or cancer.
The diagnosis and treatment of intestinal ischemia varies somewhat depending on the particular patient, suspected source, and clinical situation. What is consistent and clear, however, is that early diagnosis is essential to improve the chances for a good outcome. In general, the longer the injury is sustained without treatment, the greater the chance that the damage done to the intestines will be irreversible.
The first considerations for a physician in diagnosing intestinal ischemia are the patient’s past medical history, his or her current symptoms, and results of a thorough physical examination. The diagnostic tools most commonly used to supplement this information include routine blood tests, colonoscopy, ultrasound, abdominal radiologic studies including CAT or MRI scans, mesenteric angiography, and exploratory abdominal surgery. Angiography is a special radiologic study of one’s blood vessels. Contrast material is injected through a small catheter placed into an abdominal artery or vein, after which radiologic images of the vessels are generated.
In acute small intestinal ischemia, particularly cases caused by arterial blockage, initial management of the patient includes addressing the relevant underlying and precipitating medical conditions, intravenous or “IV” fluids, and antibiotics to prevent possible infection. Angiography is considered the gold standard for diagnosis and is usually performed after a CT scan has shown that the abdominal pain is not caused by any other disorder that is mimicking intestinal ischemia. Sometimes a CT-angiogram, which is a non-invasive way of studying the intestine and its blood vessels, obviates the need for a formal angiographic study. Afterwards, a treatment decision is made based largely upon the findings on angiography and the physician’s assessment of the patient’s clinical status. If a significant embolus or thrombus is found in a blood vessel and the patient appears ill, a laparotomy (open abdominal surgery) or laparoscopy (exploration of the abdomen through an endoscopic tube inserted into the abdominal cavity) generally is recommended either to remove the obstruction in the blood vessel or to create a bypass route for blood around the blockage. If, at the time of surgery, the surgeon finds segments of the intestine that are necrotic, that portion of bowel is resected (removed), and the portions of the intestine above it and below are reconnected. A second operation may be performed within 24 hours to see if the now treated blood vessels have allowed previously injured portions of the intestine to recover. If so, there may be no need for further resection. Medication that dilates, or widens vessels in order to improve blood flow can be given via the arterial catheter put in place during angiography, usually prior to, but occasionally after, surgery.
When a venous obstruction is suspected, CT scan has been used successfully for diagnosis. Angiography can be used more selectively to aid in treatment of a particular vein. When patients are demonstrated to have a thrombus in a vein and are not considered to have signs of infarction, anticoagulant (“blood thinning”) drugs, and/or medication aimed toward dissolving the clot can be used. If a patient develops signs of more threatening ischemia, surgery is indicated to remove clots and any unsalvageable segments of the intestines, as discussed above.
In cases of non-occlusive intestinal ischemia, there is no identifiable point of blockage seen by angiography. Rather, the blockage is caused by diffuse spasm in the blood vessels supplying the intestines and the spasm is precipitated by underlying medical conditions such as heart failure, cardiac arrhythmias, and hypotension; these underlying conditions must be addressed to help restore blood delivery to the intestines. Patients with vasospasm may benefit from by administration of a vasodilator through a catheter directly placed in the main blood vessel supplying the intestine to break the spasm and thereby improve intestinal blood flow.
In colon ischemia, the extent and severity of the injury again dictates the action taken. If the patient is stable, colonoscopy is ideally performed within 24-48 hours of the onset of symptoms. Patients in this situation can expect to be placed on a restricted diet in the short-term, and given antibiotics to prevent serious infection. In most cases, symptoms abate within 1 to 2 days and the injury to the colon resolves in 1 to 2 weeks. A minority of patients develop more significant consequences and are treated accordingly, possibly with surgery.
The complications of angiography and medication infusion by catheter have included transient, reversible kidney problems, and bruising at sites of catheter insertion. With more significant surgical procedures there are, of course, additional risks. However, the alternative of delayed diagnosis in treatment of intestinal ischemia, particularly in cases of acute small intestinal ischemia, offers far more devastating consequences. Such delay, particularly of waiting until intestinal infarction develops, carries a mortality rate of 70%-90%. At medical centers that routinely treat patients with intestinal ischemia more than 50% of the patient can survive with an aggressive approach, using early diagnosis and prompt therapy with vasodilators and surgery; more than 75% of patients treated in this way have lost no more than a small fraction of their intestineshe importance of early diagnosis is demonstrated by the fact that 90% of patients who were ultimately diagnosed with acute small intestinal ischemia, but who had not developed late signs of ischemic damage such as peritonitis (inflammation of the tissue lining the inside of the abdomen), survived this injury. In other words, people who sought out their physicians and who had their disease diagnosed at an early stage of intestinal ischemia had a much better outcome than those in whom diagnosis was made late.
Lawrence J. Brandt, M.D., MACG, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY and Paul Feuerstadt, MD, Gastroenterology Center of Connecticut, Hamden, CT – Updated December 2012.
Lawrence J. Brandt, MD, MACG, FACP, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY – Updated April 2007.
Lawrence J. Brandt, MD, MACG, FACP and Lawrence S. Rosenthal, MD, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY – Published October 2002.