Congenital megacolon

浙江大学医学院附属儿童医院

江米足

Definition

Also called: Hirschsprung disease, HD

Description: characterized by the absence of myenteric and s

ubmucosal ganglion cells in the distal intestine; usually affects the last 1-2 feet of the colon, causes problems with the movement in the affect

ed bowel segment, results in an obstruction of the bowel.

Organs involved

aganglionic segment always involves rectum and extends proximally without skip areas

dilated colon found proximal to aganglionic segment

Histopathology

Absence of ganglionic cells

Hypertrophic cholinergic nerve

trunks

Limited number of adrenergic

fiber

Who is most affected infancy, may go undiagnosed for years 96% are term infants, 4% are premature infan

ts The male to female ratio is 4:1. If the entire co

lon is involved, the sex ratio is about 1:1 With an affected sibling, the incidence rises to

12-33% occurs in 0.8% of patients with trisomy 21

Down syndrome Incidence/Prevalence:

1/1,000-1,500 live births

Risk factor

Risk factors for Hirschsprung's include: Family members with the disease More common in males May be associated with other congenital

defects

Causes and pathogenesis Causes:

absence of submucosal and myenteric (muscular, Auerbach's) parasympathetic ganglion cells

Pathogenesis: neuroblasts from neural crest fail to complet

e caudal migration to Meissner's and Auerbach's plexuses

failure of relaxation/normal peristalsis dilatation of colon

Types 1

aganglionic segment limited to rectosigmoid in 80%

colon aganglionic from anus to hepatic flexure in 15% (long segment HD)

entire colon lacks ganglion cells in 3% - total colonic aganglionosis, sometimes involves variable segment of distal ileum

Type 2 Classical HD (85% of cases): Rectosegmoid Short segment HD (10% of cases) Long segment HD （ 4% of cases) Total colonic aganglionosis (1% of cases) rare variants include the following:

Total intestinal aganglionosis Ultra-short-segment HD (involving the distal r

ectum below the pelvic floor and the anus

History

Chief concern (CC): in infants and older children - overflow diarr

hea, vomiting, abdominal distention may be enterocolitis (high mortality rate)

early symptoms of megacolon range from complete acute bowel obstruction in neonates to intermittent episodes of chronic constipation in older children

History Chief concern (CC):

sometimes there is diarrhea, episodes of constipation and diarrhea may alternate with periods of apparent normality, diarrhea may develop into a fulminant enterocolitis leading to severe fluid and electrolyte imbalance

older children in severe cases may present with failure to thrive (FTT) and can be confused with malabsorption syndromes

History of present illness (HPI)

in infants and older children - suspect any patient with chronic unexplained illness with abnormal bowel pattern dating back to early infancy

delayed passage of meconium at birth Past medical history (PMH):

in infants and older children - history of obstipation, constipation, failure to thrive

Physical

General physical: in newborns - meconium ileus, intestinal obstructio

n, severe constipation, bilious vomiting, delayed passage of meconium (usually passed within 24 hours, 48 hours in preemies)

Abdomen: abdominal distention, occasionally loops of stool-fi

lled bowel palpable Rectal:

increased sphincter tone, no stool in rectal vault, classically explosion of watery stool on removal of finger

What are the symptoms?

HD is usually diagnosed in infancy, but can also be found later. Symptoms can differ with age

Symptoms In newborns

Failure to pass meconium within the first 48 hours of life (Meconium is a dark sticky substance that is the first bowel movement)

Vomiting after eating Abdominal distention

In young children Severe constipation Diarrhea Anemia Growth delay

In teenagers Severe constipation for most of their lives Anemia

Rule out

intestinal atresia or stenosis, congenital duodenal obstruction

imperforate anus necrotizing enterocolitis cystic fibrosis malrotation less causes of neonatal obstruction

intussusception Meckel diverticulum duplications

medical conditions associated with bilious vomiting and ileus

sepsis hypothyroidism meconium plug syndrome

“Red flags” for HD diagnosis Delayed (>24 h) meconium —Present in 70-87% of cases of HD an

d in <1% of normal children Neonatal constipation —Present in 90-95% of cases but in <7% o

f children with functional constipation Family history (affected sibling) —Present in 12-33% of cases Poor growth—Present in 25-30% of cases Abdominal distension —Present in 76-85% of cases but in 20% of

patients with functional constipation Down’s syndrome and other chromosomal anomalies —HD is p

resent in 1.5% of patients with Down’s syndrome, but 5-10% of patients with Down’s have functional constipation

Three or more red flags are present in 18% of patients with the disease. No red flags are present in <1% of patients with the disease

Tests for HD diagnosis Barium enema —injection of fluid into the r

ectum that makes the colon show up on an x-ray

Rectal suction biopsy —removal of a sample of bowel tissue to check for ganglia, full-thickness biopsy if necessary

Anorectal manometry—measurement of the pressures of the internal and external sphincter with a rectal balloon

Plain X ray: air/fluid levels, no air in rectum

Contrast enema: -Narrow distal segment -Funnel-shaped transition zone-Dilation of proximal colon-After 24-48 hours the contrast material is in the bowel-Mucosal irregularity (enterocolitis)

Imaging studies

Abdominal x ray image

showing gaseous distension of the large bowel with air absent from the rectum (typical of HD)

Biopsy and pathology no ganglion cells in submucosal plexus confirm

s diagnosis types of rectal biopsies

seromuscular biopsy at laparotomy full-thickness transrectal biopsy requires bowel prep, general anesthesia check for Auerbach's plexus

alternative - suction biopsy small specimens, requires experienced pathologist can be done at bedside check for Meissner's plexus

Normal basal internal anal sphincteric tone No reflex relaxation of the internal

sphincter with rectal distention It can be put through safely in newborn

age as well

Anorectal manometry

The rectoanal inhibitory reflex

Other diagnostic testing Fingerprint chromatogram model of serum

protein (3 protein markers) had 100% sensitivity and 100% specificity for identifying HD in 78 serum specimens (42 of HD, 16 of adhesive ileus and 20 normal controls)

Treatment

The primary treatment for HD is surgery to remove the affected portion of the colon.

There are three potential phases to the surgery, but all three phases may not be needed.

Your doctor will discuss the best methods for you or your child's condition.

Surgery Colostomy—This involves surgically creating

an opening into the colon, which is brought to the abdominal surface. Stool contents are excreted through this opening and into a bag.

Pull-through operation—The affected area of the colon is removed, then the healthy colon is brought down to the rectum and joined to the rectal wall.

Closure of the colostomy—The colostomy opening is closed, and bowel function gradually returns to normal.

Transanal Endorectal Pull-Trough It can be performed safely in

infant as well Generally one-stage surgery No abdominal phase The anastomosis is happening in a

“ safe” place at the pectinate line

Treatment

Operative sequelae Enterocolitis rare but up to 60% mortality Perforation of the intestine Short gut syndrome Anal dilation may be intermittently necessa

ry if constipation secondary to retained aganglionic internal anal sphincter

Occasional incontinence and fecal soiling

Outcome

Symptoms are eliminated in 90% of children after surgical treatment.

A better outcome is associated with early treatment, and shorter bowel segment involvement.