Gastroparesis: Causes
Gastroparesis: Causes
Causes
Your stomach is a muscular sac located in the upper middle of your abdomen, just below your ribs. If you're an average adult, it's about the size of a small melon, but can stretch to hold nearly 1 gallon of food and liquid. Your stomach folds in on itself when it's empty and expands when you eat or drink.
The walls of your stomach are lined with three layers of powerful muscles that mix food with enzymes and acids produced by glands in your stomach's inner lining. Once the food is thoroughly pulverized — reduced to the consistency of porridge — strong muscular contractions (peristaltic waves) push it toward the pyloric valve, which leads to the upper portion of your small intestine (duodenum), where the real work of digestion takes place. The valve opens just enough to release a scant eighth of an ounce of food at a time.
It may take three to four hours for your stomach to empty after you eat, depending on your diet — foods high in fat can prolong the emptying time considerably. The slowness of the process ensures that food is thoroughly mixed with digestive juices for the best possible absorption.
Why the stomach stops working
Arguably the most important nerve in your body, the vagus nerve stretches from your brainstem to your colon. It helps orchestrate the complex microcircuits in your digestive tract, including signaling the smooth muscles in your stomach to contract in peristaltic waves — usually at the rate of about three contractions a minute. When these contractions slow or stop completely, food doesn't move out of your stomach into the duodenum as it should.
Damage to the vagus nerve is the leading cause of gastroparesis, although the disorder can also result from damage to the stomach muscles themselves. Factors that can damage nerves or muscles in your stomach include:
* Diabetes. Affecting people with either type 1 diabetes or type 2 diabetes, this is one of the most common causes of gastroparesis. Over time, high blood glucose levels and their metabolic effects can damage the vagus nerve and disrupt its normal functioning. Once gastroparesis develops, diabetes often becomes worse because erratic stomach emptying and poor absorption make blood sugar levels harder to control.
* Surgery. Operations involving your esophagus, stomach or upper part of your small intestine can injure the vagus nerve and lead to gastroparesis. Symptoms may develop immediately after the surgery or appear years later.
* Medications. Many commonly prescribed drugs slow stomach emptying. Chief among these are narcotic pain medications, tricyclic antidepressants and calcium channel blockers. Antacids that contain aluminum hydroxide, some high blood pressure medications and the psychiatric drug lithium also can disrupt the normal functioning of the stomach. Symptoms usually improve once you stop taking the medication.
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Cancer treatments. Nausea and vomiting are common side effects of chemotherapy because most anti-cancer drugs target fast-growing cells throughout your body, including healthy cells in your intestinal tract. The nausea and vomiting are usually temporary and improve when treatment ends.
But some people receiving high doses of chemotherapy drugs may develop intractable nausea and vomiting as a result of chemotherapy-induced gastroparesis. In that case, problems with the stomach being able to move food (motility problems) originate in the nausea center of the brainstem, just above the spinal cord. Radiation therapy to the chest and abdomen also can cause gastroparesis.
* Other disorders. A number of other medical conditions can cause gastroparesis, including anorexia and bulimia, the connective tissue disease scleroderma, Parkinson's disease and other nervous system illnesses, and metabolic disorders such as hypothyroidism. For reasons that aren't clear, some otherwise healthy people develop gastroparesis after a bout of the flu or other viral illness.
By Mayo Clinic Staff
Nov. 21, 2007
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