Գլխավոր Հիվանդություններ Hirschsprung's disease

Hirschsprung's disease (HD) 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. About 10% of cases are familial.

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. In some extremely rare cases, the absence of ganglion cells continues to spread after the corrective surgery, resulting in multiple surgeries. Those patients that also have thyroid cancer may be able to digest food properly, but may not be able to use the nutrients properly. Other genes Common and rare DNA variations in the Neuregulin 1 (NRG1) and NRG3 (NRG3) were first shown to be associated with the disease in Chinese patients through a Genome Wide Association Study (GWAS) by the Hong Kong team in 2009 and 2012 respectively Subsequent studies in both Asian and Caucasian patients confirmed the initial findings by the University of Hong Kong. Both rare and common variants in these two genes have been identified in additional Chinese,[11] Thai, Korean, Indonesian and Spanish patients. These two genes are known to play a role in the formation of the enteric nervous system, thus, they are likely to be involved in the pathology of Hirschsprung, at least in some cases. Treatment Treatment of Hirschsprung's disease consists of surgical removal (resection) of the abnormal section of the colon, followed by reanastomosis. Swenson, Soave, Duhamel, and Boley procedures Orvar Swenson, who discovered the cause of Hirschsprung’s, first performed its surgical treatment, the pull-through surgery in 1948. The pull-through procedure repairs the colon by connecting the functioning portion of the bowel to the anus. The pull-through procedure is the typical method for treating Hirschsprung’s in younger patients. Swenson devised the original procedure, and the pull-through surgery has been modified many times. Currently, there are several different surgical approaches, which include the Swenson, Soave, Duhamel, and Boley procedures. The Swenson procedure leaves a small portion of the diseased bowel. The Soave procedure leaves the outer wall of the colon unaltered. The Boley procedure is a small modification of the Soave procedure, so the term Soave-Boley procedure is sometimes used. The Duhamel procedure uses a surgical stapler to connect the good and bad bowel. For the 15 percent of children who do not obtain full bowel control, other treatments are available. Constipation may be remedied by laxatives or a high fiber diet. In those patients, serious dehydration can play a major factor in their lifestyle. A lack of bowel control may be addressed by a stoma, similar to a colostomy. The Malone antegrade colonic enema (ACE) is also an option. In a Malone ACE, a tube goes through the abdominal wall to the appendix or, if available, to the colon. The bowel is then flushed daily. Children as young as 6 years of age may administer this daily flush on their own. If the affected portion of the lower intestine is restricted to the lower portion of the rectum, other surgical procedures may be performed, such as a posterior rectal myectomy. The prognosis is good in 70 percent of cases. Chronic post-operative constipation is present in 7 to 8 percent of the operated cases. Post-operative enterocolitis is a severe manifestation that is present in the 10%–20% of operated patients.

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