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By Mayo Clinic staffIn dumping syndrome, food and juices from your stomach move to your small intestine in an unregulated, abnormally fast manner. This accelerated process is most often related to changes in your stomach associated with surgery. For example, when the opening (pylorus) between your stomach and the first portion of the small intestine (duodenum) has been damaged or removed during an operation, the syndrome may develop.
Dumping syndrome may occur at least mildly in one-quarter to one-half of people who have had gastric bypass surgery. However, fewer than 5 percent have severe symptoms. It develops most commonly within weeks after surgery, or as soon as you return to your normal diet. The more stomach removed or bypassed, the more likely that the condition will be severe. It sometimes becomes a chronic disorder.
Gastrointestinal hormones also are believed to play a role in this rapid dumping process.