Hirschsprung disease (congenital aganglionic megacolon) is a functional bowel obstruction characterized by congenital absence of enteric ganglion cells in the distal bowel. Arrest in craniocaudal migration of neural crest cells results in an aganglionic segment of variable length extending from the rectum proximally. The aganglionic segment remains in sustained contraction (tonic contraction), and the proximal normally innervated bowel dilates (megacolon). Presents in term neonates with delayed meconium passage (>48 hours), abdominal distension, and feeding intolerance. Contrast enema is the primary imaging modality — transition zone (TZ: area of transition from aganglionic narrow segment to ganglionic dilated segment) and abnormal rectosigmoid index (<1.0) are observed. Definitive diagnosis is by rectal biopsy (absence of ganglion cells + hypertrophied nerve fibers). Treatment is surgical pull-through procedure (Soave, Duhamel, or Swenson).
Age Range
0-2
Peak Age
0.05
Gender
Male predominant
Prevalence
Uncommon
Hirschsprung disease is fundamentally a developmental disorder of the enteric nervous system. During embryological development, neural crest cells migrate craniocaudally from the esophagus to the rectum during gestational weeks 5-12, forming the myenteric (Auerbach) and submucosal (Meissner) plexuses. This migration can arrest at any level — ganglion cells cannot reach distal to the arrest point, creating an aganglionic segment. Without ganglion cells, normal relaxation reflex (rectoanal inhibitory reflex — RAIR) does not function — the internal sphincter cannot relax and the bowel segment remains in tonic contraction. The proximal normally ganglionated bowel generates vigorous peristaltic movements against the narrow distal segment and progressively dilates (megacolon). The transition zone on contrast enema represents the area of transition from aganglionic narrow to ganglionic dilated segment. The rectosigmoid index (rectum diameter / sigmoid diameter) is normally >1.0 (rectum wider than sigmoid) — in Hirschsprung it is <1.0 (narrow rectum, dilated sigmoid). Irregular contractions reflect uncoordinated muscle activity in the aganglionic segment.
The transition zone is the most characteristic radiologic finding of Hirschsprung disease on contrast enema. It represents the caliber change point between the aganglionic narrow segment and ganglionic dilated segment. Better visualized on lateral projection. TZ location is critical for surgical planning — determines the proximal boundary of the aganglionic segment. Rectosigmoid TZ is most common (75-80%), followed by sigmoid (15%), descending colon (5%), transverse/ascending colon (3%), and total colonic (2-5%). TZ may not always be clearly visualized — particularly in the neonatal period and total colonic Hirschsprung. In these cases, 24-hour delayed film and rectal biopsy are decisive.
When contrast material (barium or water-soluble contrast) is administered retrograde via the rectum during contrast enema, the transition zone (TZ) between the aganglionic narrow segment and ganglionic dilated segment is visualized. The TZ is the area showing marked change in colon caliber — distal narrow segment (aganglionic) transitions to proximal dilated segment (ganglionic). TZ location determines disease length: rectosigmoid (75-80%), long segment (10-15%), total colonic (5-10%). Lateral projection provides better TZ visualization. Important: contrast enema should be performed without preparation (no cleansing enema) — cleansing can dilate the rectum and mask the TZ.
Report Sentence
A transition zone is seen at the ___ level on contrast enema, with the distal narrow segment transitioning to the proximal dilated segment; findings are consistent with Hirschsprung disease.
The rectosigmoid index (RSI) is the ratio of the widest rectal diameter to the widest sigmoid diameter. In normal children, the rectum is wider than the sigmoid (RSI >1.0). In Hirschsprung disease, the rectum remains narrow as it is aganglionic and the sigmoid dilates (RSI <1.0). RSI is measured on the lateral contrast enema film. RSI <1.0 has diagnostic sensitivity of 73-80% and specificity of 80-90%. However, in the neonatal period (<1 month), RSI may not yet be discriminatory as megacolon may not have developed. In this case, the 24-hour delayed film is more useful.
Report Sentence
On lateral contrast enema film, the rectosigmoid index is calculated as ___ (<1.0), with the rectum appearing narrower than the sigmoid; this finding supports Hirschsprung disease.
The delayed film taken 24 hours after contrast enema is an important finding with high sensitivity for Hirschsprung diagnosis. Normal bowel completely evacuates barium within 24 hours — in Hirschsprung, barium is persistently retained due to functional obstruction in the aganglionic segment. This finding plays a critical diagnostic role especially when the transition zone is unclear in the neonatal period. 24-hour retention has >80% sensitivity and >85% specificity for diagnosis. Even in total colonic Hirschsprung, 24-hour retention may be positive (even when TZ is not visible).
Report Sentence
On the delayed film taken 24 hours after contrast enema, barium retention is observed in the colon lumen; this finding indicates functional bowel obstruction and is consistent with Hirschsprung disease.
During fluoroscopic observation of contrast enema, irregular, uncoordinated contractions may be seen in the aganglionic segment. While normal bowel shows regular peristaltic waves, the aganglionic segment shows spastic, irregular contractions — reflecting absence of ganglionic coordination. May also be described as 'saw-tooth' or 'zigzag' contour. This finding is not always prominent but supports diagnosis when observed.
Report Sentence
On fluoroscopic observation, irregular, uncoordinated contractions are seen in the aganglionic segment; this finding indicates absence of normal ganglionic peristalsis.
AXR shows distal bowel obstruction pattern: dilated proximal colon and small bowel loops, air-fluid levels present, decreased or absent gas in rectum. In the neonatal period, this pattern is not specific to Hirschsprung and may result from various distal obstruction causes (meconium plug, small left colon syndrome, anorectal malformation). However, combined with delayed meconium passage >48 hours in a term neonate, this pattern strongly suggests Hirschsprung. AXR alone is not diagnostic — confirmation with contrast enema is required.
Report Sentence
AXR shows dilatation of proximal colon and small bowel loops with air-fluid levels, with decreased rectal gas; findings are consistent with distal bowel obstruction.
Criteria
Aganglionic segment limited to rectum and distal sigmoid. 75-80% of cases. Most common type. Rectosigmoid transition zone prominent on contrast enema.
Distinct Features
Type with the best surgical prognosis. Single-stage transanal pull-through (Soave or De la Torre) can be performed. Postoperative functional outcomes are excellent — 90%+ of patients achieve continence.
Criteria
Aganglionic segment extends proximal to the sigmoid (up to or beyond the splenic flexure). 10-15% of cases.
Distinct Features
Surgery is more extensive — long-segment resection required. Two-stage procedure frequently applied (colostomy first, then pull-through). Long-term soiling and enterocolitis risk is higher.
Criteria
Entire colon + variable length of small bowel is aganglionic. 2-5% of cases. Transition zone may not be visible on contrast enema — colon may appear normal or short ('question mark' colon).
Distinct Features
Most difficult type to diagnose — contrast enema may be misleading. Rectal biopsy mandatory for diagnosis. Surgery requires extensive colectomy + ileal pull-through. Short bowel syndrome and nutritional complications may develop. Most serious prognosis.
Distinguishing Feature
In meconium plug syndrome, the meconium plug is expelled with contrast enema and obstruction resolves — in Hirschsprung there is permanent functional obstruction. No transition zone in meconium plug, RSI is normal. Follow-up recommended after meconium plug to exclude Hirschsprung (5-15% association).
Distinguishing Feature
NEC occurs in premature infants, pneumatosis intestinalis and portal venous gas are specific to NEC. Hirschsprung typically presents in term infants, pneumatosis is absent. NEC presents with acute sepsis, Hirschsprung with chronic obstruction.
Distinguishing Feature
In anorectal malformation, anal opening anomaly is detected on physical exam (imperforate anus, ectopic anus, fistula). In Hirschsprung, anal anatomy is normal but functional obstruction is present. Contrast enema may not be possible in anorectal malformation or may show a fistula.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralHirschsprung disease is a chronic functional obstruction requiring surgical treatment. Diagnosis is confirmed with contrast enema + rectal biopsy (absence of ganglion cells). Surgical treatment is pull-through procedure — aganglionic segment is resected and normally ganglionated bowel is anastomosed to the anus. Three classic techniques: Soave (endorectal), Duhamel (retrorectal), Swenson (rectosigmoidectomy). Laparoscopy-assisted transanal pull-through is the modern approach. Preoperative decompression is important — Hirschsprung-associated enterocolitis (HAEC) can be life-threatening (20-30% incidence). HAEC signs: fever, abdominal distension, explosive diarrhea, sepsis — requires emergency decompression and antibiotics. Postoperative complications: anastomotic leak, stricture, enterocolitis, soiling (incontinence). Long-term 85-90% of patients have good functional outcomes. Strong association with Down syndrome (2-10% co-occurrence) — all Down syndrome infants should be screened for Hirschsprung.
An important cause of congenital intestinal obstruction. Delayed diagnosis can result in Hirschsprung enterocolitis (toxic megacolon), which is life-threatening. Contrast enema is the primary diagnostic modality, but definitive diagnosis requires rectal biopsy. Meconium delay beyond 48 hours in the neonatal period is strongly suspicious. Strong association with Down syndrome should be screened. Pull-through surgery is curative, but long-term continence issues may occur.