What Causes Intestinal Ischemia?

Intestinal ischemia is a group of conditions that happen when intestinal blood flow decreases because of a blocked blood vessel. The small and large intestines can both be affected by intestinal ischemia. It is a serious condition that results in pain and makes it hard for the intestines to function normally. Severe cases can result in damage to the intestinal tissues and can result in death. Intestinal ischemia can also cause the development of a hole in the intestines or perforation causing peritonitis or sepsis. Sometimes the body is able to heal itself from intestinal ischemia. However, during the healing process, the body develops scar tissues that block or narrow the intestines. Treatment for intestinal ischemia focuses on restoring the supply of blood to the digestive tract. Depending on the underlying cause, certain medications and surgery may be needed to restore normal intestinal function.

Hypotension

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Hypotension is a condition characterized by abnormally low blood pressure level under 90/60. Most cases of low blood pressure that do not produce symptoms are harmless. However, some cases can indicate a more serious underlying condition and can result in health problems associated with a lack of adequate blood supply. Heart failure, severe trauma, going into shock, the use of certain medications, chronic kidney failure, or major surgery can all cause dangerously low blood pressure. This means oxygenated blood flow will not make it to all of the tissues around the body the way it should. If the blood flow to the small intestine becomes abruptly slowed due to low blood pressure, acute mesenteric ischemia occurs. When low blood pressure levels result in the impeded flow of blood to the large intestine or colon, ischemic colitis or colon ischemia occurs. Symptoms that occur in a patient who has hypotension precipitated acute intestinal ischemia include sudden abdominal pain, an urgent need for a bowel movement, abdominal distension, mental confusion, and frequent bowel movements.

Bowel Twisting

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Abnormal bowel twisting or volvulus occurs when a region of the small intestine or the colon twists. The intestine can twist around the tissues that hold it in place, or it can rotate around itself. This twisting will keep liquid and food from being able to pass through the affected area. When food is unable to move through a part of the lower digestive tract, it is considered an intestinal or bowel obstruction. The most common variation of this condition is called sigmoid volvulus, which occurs when the sigmoid or the last part of the colon becomes twisted. Another common location this condition occurs in is the cecum or the beginning of the large intestine, which is called cecal volvulus. When the twisting results in an obstruction of blood flow and stops the passing of normal intestinal contents, intestinal ischemia will happen. If volvulus triggered ischemia occurs, surgical intervention is needed to prevent another volvulus. Should a volvulus triggered ischemia go untreated, affected parts of the intestines can die from a lack of oxygen.

Vasculitis

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When the blood vessels become inflamed, the condition is called vasculitis. This results in changes in the walls of the blood vessels such as narrowing, scarring, and thickening. Vasculitis can affect several organs or a single organ, as well as capillaries, arteries, and veins. This condition happens when the immune system within the body attacks healthy blood vessels, resulting in inflammation. The general narrowing and thickening of blood vessels can keep adequate amounts of oxygen-rich blood from reaching numerous tissues throughout the body. In addition, the thickening and narrowing of the arteries, veins, or capillaries that occurs with vasculitis will make the affected blood vessels significantly more vulnerable to blood clots. The mesenteric arteries are the main blood vessels that supply the intestines with oxygenated blood. When these vessels become affected by vasculitis, intestinal ischemia can occur. Treatment for intestinal ischemia caused by vasculitis will include the use of anti-inflammatory medications, corticosteroid medications, and chemotherapy. Suppressing the immune response causing vasculitis can help restore blood flow to the affected area of the intestine.

Blood Clots

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Blood clots are the clumps of blood the body forms in response to a cut or an injury to plug the injured blood vessel. In healthy individuals, clots are a natural mechanism that stops the body from losing too much blood. However, the process that causes the formation of clots can be impaired by several different diseases and conditions. This impairment can result in the formation of clots inside the blood vessels that do not naturally dissolve on their own. These blood clots can break free and flow throughout the bloodstream until they become lodged or stuck. Numerous dangerous conditions can occur when a blood clot becomes lodged in an artery. These adverse conditions depend on the location of where it is blocking normal blood flow. A blood clot can make its way into the mesenteric arteries or the arteries that supply the intestines with oxygenated blood and become lodged. This obstruction will stop the normal flow of blood to parts of the colon or small intestine. Intestinal ischemia caused by lodged blood clots will most often require surgery to restore adequate blood flow. In minor cases, medication may be used in an attempt to dissolve existing clots before implementing surgical interventions.

Pancreatitis

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Pancreatitis is a disease that causes inflammation of the pancreas. This inflammation can happen as a result of the premature activation of digestive enzymes. Because the activation occurs before these enzymes make their way into the small intestine, the enzymes end up attacking the pancreas instead of the food moving through the intestines. The result of this attack is damage and inflammation of the pancreas. The exact mechanism of how this pancreatitis causes inflammation in the mesenteric veins is not clear. However, when the damage that occurs to the pancreas also causes inflammation in the veins responsible for transporting oxygen-poor blood away from the intestines and colon, mesenteric venous thrombosis can occur. Mesenteric venous thrombosis is the blockage of a vein that results in swelling and bleeding of the intestines due to a backup of blood. The deoxygenated backup of blood stops the normal flow of oxygen-rich blood to the affected tissues. This process effectively results in the development of intestinal ischemia.


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