الفهرس 
INCIDENCE AND SPECTRUM OF HIRSCHSPRUNG DISEASEOnly 14 pages are availabe for public view
 |  | from | 104 |  |  |
| | | from | 104 | | |
Abstract
H
irschsprung’s disease (HD) is a congenital disease, which is characterized by the absence of ganglion cells (aganglionosis) in the myenteric and submucosal plexuses of the distal intestine leading to sustained contraction of the aganglionic bowel segment, leading to intestinal obstruction and distension of proximal segments (megacolon).
The incidence of HD ranges from 1/5000 to 1/10,000 live births. In 67–82 % of cases the aganglionic segment involves the recto-sigmoid only “typical HD”, while in about 15–25 % of the cases, the aganglionosis affects longer segments up to the splenic flexure or even the transverse or right colon; this is called “long segment Hirschsprung’s disease.”. About 3–8 % of the patients suffer from aganglionosis of the entire colon including segments of the terminal ileum which is called “total colonic aganglionosis”.
The typical clinical presentation of Hirschsprung disease involves abdominal distension, bilious vomiting and feeding intolerance suggestive of distal bowel obstruction during the neonatal period. Delayed passage of meconium beyond the first 24 hours is characteristic but is absent in approximately 10% of children with Hirschsprung disease.
Some patients present later in childhood, or even during adulthood, with chronic constipation. This is most common among breast-fed infants, who typically develop constipation around the time of weaning
Approximately 10% of children with Hirschsprung disease present with fever, abdominal distention, and diarrhea due to Hirschsprung-associated enterocolitis (HAEC), which may be severe and life-threatening.
There are three main diagnostic modalities used to screen for and confirm the diagnosis of Hirschsprung disease; they include the contrast enema, anorectal manometry and rectal biopsy.
A contrast enema is usually the first diagnostic test recommended in newborns with a clinical picture of obstruction. It is useful as a diagnostic tool to evaluate for HD as well as to exclude other conditions such as meconium ileus, intestinal atresia, and meconium plug syndrome. In addition, for conditions such as meconium plug or meconium ileus, it can also be therapeutic.
There are several diagnostic indexes of contrast enema used to diagnose HD. Among these indexes, only transition zone detection, recto-sigmoid index (RSI), and delayed evacuation beyond 24 hours have sensitivities greater than 50%.
RSI and transition zone detected in a contrast enema are the most accurate parameters in guiding the diagnosis towards Hirschsprung disease, yet they alone do not confirm the diagnosis.
Anorectal manometry (ARM) offers a non-invasive method for diagnosing HD. This procedure has the advantage of being able to be done at the bedside or as an outpatient procedure and is associated with no complications. Its limitations include the need for the patient being in a normal physiologic and quiet state to avoid numerous artifacts.
Today, it is mainly used in children older than 1 year of age in whom the etiology of constipation remains unclear and/or a contrast enema and rectal biopsy have been uninformative with a sensitivity and specificity of 91% and 94% respectively for diagnosing HD, yet the diagnostic accuracy of ARM drops in infants younger than one year of age.
The most accurate modality for the diagnosis of HD is rectal biopsy with careful examination of the biopsy specimen by a qualified pathologist.
A rectal biopsy can be obtained using the open technique “full thickness biopsy (FTB)”, by using a suction device “rectal suction biopsy (RSB)” or endoscopically using a biopsy forceps.
Today, RSB is widely considered the gold standard in the diagnostic work-up of patients with suspected HD, allowing specimens to be taken safely without general anesthesia on the ward or as an out-patient procedure. The mean sensitivity and specificity rates of RSB was reported to be 97 and 99 %, respectively with an overall complication rate of 0.65%.
Techniques for histopathological examination of a rectal biopsy include conventional (H&E) staining, Acetylcholinesterase histochemistry and Immuno-histochemistry.
Using an age-related diagnostic approach is justified by the necessity to use the most accurate test (RSB) in neonates and infants less than one-year-old because of less reliability of the ARM, the higher incidence of HD and the risk of severe enterocolitis; but in the older children, ARM is a preferable test for acquiring important information about physiopathology of constipation and possibility to select the cases for undergoing RSB.
The main objective in the treatment of patients with Hirschsprung disease is to resect the aganglionic bowel and pull down normo-ganglionic bowel that must be anastomosed to the rectum above the anal canal, preserving the part of the bowel where the sensitivity exists and preserving the sphincter mechanism (anal canal). All techniques, regardless of its specific maneuvers, must follow these basic principles.
Surgery for HD can be done via a combined abdominal and transanal approach “Swenson, Soave and Duhamel procedures” or it can be done via minimally invasive techniques including laparoscopic and transanal approaches.