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Hirschsprung's disease or Hirschsprung disease (HD), also called congenital megacolon or congenital aganglionic megacolon, is a form of megacolon that occurs when part or all of the large intestine or antecedent parts of the gastrointestinal tract have no ganglion cells and therefore cannot function. During normal prenatal development, cells from the neural crest migrate into the large intestine (colon) to form the networks of nerves called the myenteric plexus (Auerbach plexus) (between the smooth muscle layers of the gastrointestinal tract wall) and the submucosal plexus (Meissner plexus) (within the submucosa of the gastrointestinal tract wall). In Hirschsprung's disease, the migration is not complete and part of the colon lacks these nerve bodies that regulate the activity of the colon. The affected segment of the colon cannot relax and pass stool through the colon, creating an obstruction. In most affected people, the disorder affects the part of the colon that is nearest the anus. In rare cases, the lack of nerve bodies involves more of the colon. In five percent of cases, the entire colon is affected. Stomach and esophagus may be affected too. Hirschsprung's disease occurs in about one in 5,000 of live births. It is usually diagnosed in children, and affects boys more often than girls. ==Signs and symptoms== Typically, Hirschsprung's disease is diagnosed shortly after birth, although it may develop well into adulthood, because of the presence of megacolon, or because the baby fails to pass the first stool (meconium)〔 within 48 hours of delivery. Normally, 90% of babies pass their first meconium within 24 hours, and 99% within 48 hours. Other symptoms include green or brown vomit, explosive stools after a doctor inserts a finger into the rectum, swelling of the abdomen, lots of gas and bloody diarrhea. Some cases are diagnosed later, into childhood, but usually before age 10.〔 The child may experience fecal retention, constipation, or abdominal distention.〔 With an incidence of one in 5,000 births, the most cited feature is absence of ganglion cells: notably in males, 75 percent have none in the end of the colon (recto-sigmoid) and eight percent lack ganglion cells in the entire colon. The enlarged section of the bowel is found proximally, while the narrowed, aganglionic section is found distally, closer to the end of the bowel. The absence of ganglion cells results in a persistent over-stimulation of nerves in the affected region, resulting in contraction. Some, extremely rare cases, the absence of ganglion cells continues to spread after the corrective surgery, resulting in multiple surgeries. Usually, the over-stimulated colon will actually absorb little, or no nutrition to benefit the patient. Those patients that also have thyroid cancer, may be able to digest food properly, but may not be able to use the nutrients properly. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hirschsprung's disease」の詳細全文を読む スポンサード リンク
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