Pathophysiology & Risk Factors

Hirschsprung disease (congenital aganglionic megacolon) is the absence of parasympathetic ganglion cells in a segment of colon, most commonly the rectosigmoid. The aganglionic segment cannot perform peristalsis, creating a functional obstruction; stool backs up and the normal bowel proximal to it dilates massively. Key distinction: the tight, constricted distal segment is the diseased portion, not the dilated proximal colon above it.

Why stool stops moving

Absent ganglion cellsdistal colon, usually rectosigmoid
No peristalsis in segmentaganglionic bowel can't propel stool
Functional obstructionstool cannot pass the tight segment
Proximal megacolonnormal bowel above dilates

Signs & Symptoms

EarlyProgresses →

failure to pass meconium within 48 hours Hallmark

cardinal newborn sign in a term infant

abdominal distension

bile-stained emesis

nonspecific; suggests obstruction

poor feeding

Late / Severe

chronic constipation

ribbon-like stools

foul-smelling stools

failure to thrive

Diagnostics & Labs

Diagnostic

rectal suction biopsy Hallmark

confirms diagnosis; shows absent ganglion cells

abdominal X-ray

proximal dilation above the obstruction

Monitor

abdominal girth measurement

Interventions & Priorities

maintain NPO status

preoperative bowel rest

NG tube decompression

IV fluids

monitor abdominal girth

assess for enterocolitis

most dangerous complication

Treatments & Medications

pull-through procedure

definitive surgical resection of the aganglionic segment

temporary colostomy

staged repair; typically not permanent

Patient Teaching

report explosive diarrhea

enterocolitis can occur months after surgery

report fever

report abdominal distension

apply barrier cream after every stool

frequent acidic stool breaks down perianal skin

expect looser, more frequent stools post-repair

normal colon adaptation, not surgical failure

Complications

Hirschsprung vs pyloric stenosis

Hirschsprung diseasePyloric stenosis

Predominant patternStooling problem (obstruction)Vomiting problem

VomitingBile-stained emesisProjectile, non-bilious

StoolNo meconium, ribbon-likeNormal then decreased

Classic exam clueDistended abdomenOlive-shaped mass, hungry infant

Hirschsprung disease

Predominant pattern: Stooling problem (obstruction)
Vomiting: Bile-stained emesis
Stool: No meconium, ribbon-like
Classic exam clue: Distended abdomen

Pyloric stenosis

Predominant pattern: Vomiting problem
Vomiting: Projectile, non-bilious
Stool: Normal then decreased
Classic exam clue: Olive-shaped mass, hungry infant

Report Nowescalate immediately

explosive foul-smelling diarrhea Hallmark

enterocolitis; NOT improved motility

fever

worsening abdominal distension

lethargy

signs of shock

can progress to sepsis and death

Clinical Pearl

No meconium in 48 hours + distended belly = think Hirschsprung. The tight segment is the sick segment — the big bowel above it is just the backup. And explosive diarrhea here isn't recovery; it's enterocolitis, a medical emergency.

Hirschsprung Disease