Congenital Megacolon Hirschsprungs disease R 3 Incidence n

Congenital Megacolon (Hirschsprung’s disease) 소아과 R 3 안선영

Incidence n absence of ganglion cells in the bowel wall beginning in the internal anal sphincter and extending proximally n 1/5000 live births n M: F = 4: 1 n Racial distribution similar

Embryology and Etiology n Neuroenteric cells migrate from neural crest to upper end of alimentary tract and proceed in distal direction n 12 th week : migration to distal colon – first into myenteric (Auerbach’s plexus) then into submucosal plexus n Embryologic defect

n Failure of neural crest migration n Immunologic mechanism: increased expression of class II antigens in the mucosa and submucosa-> causes fetus to mount an immunologic response against the neuroblast n Genetic factors: May affect more than one family member in 3 -7% of cases n Deletion in the RET gene chromosome 10 q 11 and EDNRB gene located on 13 q 22 and EDN 3 gene (major role in the development of the enteric nervous system)

Pathology n Neonatal period: intestine is normal n Proximal ganglionic intestine hypertrophies and becomes thicker and longer than normal n Taeniae disappear and longitudinal muscle layer completely surrounds colon n Distal intestine: absence of ganglion cells in the submucosal (Meissner’s) plexus and myenteric (Auerbach’s) plexus n Marked increase in nerve fibers which extend into the submucosa (seen with acetylcholinesterase stain) n Aganglionosis extends to rectosigmoid region in 80% of cases

Clinical Symptoms n Should be considered in any child who has history of constipation dating to newborn period n 90% of cases diagnosed in newborn period n Most common presentation in newborns: delayed stool passage within first 48 hrs of life n Constipation, abdominal distension, poor feeding and vomiting n Constipation followed by explosive diarrhea, failure to thrive n in older children, large fecal mass palpable in left lower quadrant. rectum is empty n stools: small pellets, ribbon-like, fluid consistency

n Rectal exam: normal anal tone followed by explosive discharge of feces and gas n failure to pass stool leads to dilatation of proximal bowel -> increased intraluminal pressure, decreased blood flow and deterioration of the mucosal barrier n stasis leads to bacterial proliferation and enterocolitis with sepsis n early diagnosis important in reducing mortality

n Study of 123 patients with HD n 60% were diagnosed in neonatal period n Delayed passage of meconium (65%), abdominal distension and constipation n 17% had associated anomalies n 86% had aganglionosis extending to rectosigmoid region

Associated Anomalies n Present in 10 -30% of HD n Urogenital tract (11%), cardiovascular system (6%), GI system (6%), other malformations, cataract, cleft palate (8%) n 3% Down SD

Diagnosis I n Abdominal x-rays: air fluid levels in colon and distended loops of intestine n Barium enema: narrow distal segment and dilated proximal intestine; presence of funnel-shaped transition zone between these 2 segments (diagnostic accuracy 80 -90%) n Transition zone may not be present before 1 -2 weeks of age n significant barium remaining in colon in 24 -hr delayed film n helpful in determining level of aganglionosis n Should not be done with clinical enterocolitis: may cause perforation

Diagnosis II n Anorectal manometry: absence of relaxation reflex after distension of balloon in rectum n Diagnostic accuracy 85% n May be done at bedside or as outpatient procedure : no complications n Test unreliable in cases where gestational age plus age after birth is less than 39 weeks and weight is less than 2. 7 kg

Diagnosis III n Rectal biopsy: gold standard n Can be performed at bedside without general anesthesia n Biopsy taken at 2 cm, 3 cm, 5 cm above dentate line n Diagnostic accuracy: 99. 7% n Most common problem is inadequate specimen (insufficient amount of submucosa)

Differential diagnosis n Meconium plug SD, small left colon SD, distal ileal atresia, low imperforate anus n Neonatal sepsis, hypothyroidism, brain injury, prematurity may result in delayed passage of stool

Treatment n Decompression: nasogastric tube, rectal tubes n perform surgery after diagnosis established or perform temporary colostomy until infant is 6 -12 mos old n 3 basic surgical approaches:

1) Swenson: excise aganglionic segment and anastomose the normal proximal bowel to the rectum 1 -2 cm above the dentate line 2) Duhamel: neorectum created-> normally innervated bowel brought down behind aganglionic rectum: anterior aganglionic half with normal sensation and posterior half ganglionic with normal propulsion

3) Soave: endorectal pull- through procedure-> strip mucosa from the aganglionic rectum and bring normally innervated colon through the residual muscular cuff Ultrashort segmental HD: excision of strip of rectal muscle

Complications n Early complications: anastomotic strictures (15%), wound infections (11%), anastomotic leaks (7%) n Late complications: chronic constipation, enterocolitis, encoporesis n Good prognosis: more than 90% of children achieve normal bowel movement