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Section 14 — Neonatal Surgery Verify against local policy v1.0 · July 2026 Baylor Ed. 33 cross-checked Sept 2026

Chapter 14.6 — Anorectal Malformations & Hirschsprung Disease

Two causes of the neonate who won't pass stool · Built on pediatric-surgery references

Educational guideline — verify locally. Rectal suction biopsy is the diagnostic standard for Hirschsprung disease. Does not replace attending judgment.
BEDSIDE ACTION BOX — The Neonate Who Won't Pass Stool

1. Overview

The Core Idea

Two important causes of failure to pass stool and distal obstruction in the newborn are anorectal malformation (imperforate anus) and Hirschsprung disease (congenital aganglionosis). One is found by looking at the perineum; the other by remembering that a term baby who doesn't pass meconium in the first 48 hours needs investigation.

2. Who This Guideline Applies To

Scope
  • Newborns with an abnormal perineal exam, delayed meconium passage, or distal bowel obstruction.
  • Cross-references: intestinal obstruction (14.5); VACTERL/anomaly screen (12.x); Down syndrome (12.3).

3. Anorectal Malformations (ARM)

Key Points
  • Diagnosed on the newborn examination — perform a careful perineal inspection at birth.
  • Classify as low (often a perineal fistula, amenable to primary repair) vs high lesions.
  • High lesions typically need a diverting colostomy, then definitive posterior sagittal anorectoplasty (PSARP).
  • Screen for VACTERL — ARM travels with vertebral, cardiac, TE, renal, and limb anomalies.

4. Hirschsprung Disease

Key Points
  • Absence of ganglion cells beginning at the internal anal sphincter and extending proximally (failure of neural crest migration).
  • Presents with delayed meconium (>48 hours), distension, and bilious vomiting; associated with Down syndrome.
  • Suction rectal biopsy showing absent ganglion cells (with elevated acetylcholinesterase) is the gold standard; contrast enema may show a transition zone.
  • Definitive treatment is a pull-through procedure resecting the aganglionic segment.

5. Clinical Presentation

At the Bedside
  • ARM: absent/ectopic anus, perineal fistula, meconium in urine (rectourinary fistula in males).
  • Hirschsprung: abdominal distension, delayed meconium, bilious vomiting; explosive stool on rectal exam.
  • Enterocolitis (Hirschsprung): fever, distension, foul explosive diarrhea, sepsis — an emergency.

6. Recommended Workup

What to Check
  • ARM: perineal exam, cross-table lateral/invertogram for level, and full VACTERL screen (echo, renal/spine imaging).
  • Hirschsprung: suction rectal biopsy (diagnostic); contrast enema (transition zone) — do not do a washout first if biopsy is planned.
  • Assess for associated syndromes/anomalies.

7. Algorithm

1
Abnormal perineum?
Yes → anorectal malformation: classify low vs high, screen VACTERL, involve surgery.
2
Normal anus but no meconium >48h?
Suspect Hirschsprung → suction rectal biopsy ± contrast enema.
3
Signs of enterocolitis?
Emergency: rectal irrigations/decompression, IV antibiotics, resuscitation.
4
Definitive surgery
ARM: PSARP (± initial colostomy). Hirschsprung: pull-through.

8. Management

Approach
  • ARM low lesion: often primary anoplasty; high lesion: diverting colostomy then PSARP.
  • Hirschsprung: initial decompression (irrigations), then single- or multi-stage pull-through.
  • Hirschsprung enterocolitis: rectal irrigations, IV antibiotics, fluid resuscitation — treat urgently.
  • NPO, gastric decompression, and IV fluids during work-up as needed.
Baylor Ed. 33 practice
  • Hirschsprung disease: described by Baylor as the commonest cause of newborn intestinal obstruction; more common in boys; familial in 4–8%. Distension, emesis and no meconium by 24 h; an explosive stool after rectal examination is very suggestive. Contrast enema may show a transition zone but is inaccurate in up to 20% of newborns; retained contrast on a 24-h film also suggests it. Suction rectal biopsy (aganglionosis with hypertrophied nerve trunks) is diagnostic.
  • Rectal irrigation technique: a red rubber catheter of at least 12 Fr and a 60 mL catheter-tip syringe; instil 10–20 mL of normal saline at a time, 15–20 mL/kg in total; never force against resistance (perforation); expect at least the volume instilled back, ending with fairly clear fluid. Never use water (electrolyte disturbance). Irrigations bridge to an early pull-through; infants with other problems get a levelling colostomy guided by frozen sections, with the pull-through delayed 2–3 months or until 5–10 kg.
  • Hirschsprung-associated enterocolitis — distension, constipation or diarrhoea, explosive foul watery stool — can progress to sepsis and death before or after surgery. Teach parents to seek urgent care; repeated episodes warrant a search for retained aganglionic bowel.
  • Imperforate anus: usually found at the first examination, though a perineal ribbon of meconium or vestibular fistula may take hours to appear. A prone lateral film at 24–36 h with a marker on the anal dimple helps separate high from low. Work-up for VACTERL: echo, chest and abdominal films, renal ultrasound and spinal ultrasound (tethered cord). Perineal fistulas may be dilated or repaired by anoplasty; primary PSARP where possible; intermediate or high lesions (>1 cm) need a colostomy first. After PSARP, boys may need a Foley for 3–7 days; Hegar dilatations start 2 weeks after surgery and progress, then taper before colostomy closure. With a divided colostomy, do not include the distal stoma in the pouch — stool spilling into the distal colon cannot be evacuated and can cause sepsis. Long-term bowel management matters for constipation and incontinence.
  • Persistent cloaca (girls only, about 1 in 20,000): rectum, vagina and urethra share one channel — a single perineal opening, sometimes with a hydrocolpos mass. 50% have hydrocolpos and 90% urological problems; missed obstructive uropathy leads to urosepsis and renal failure. Early goals: find associated anomalies (abdominal/pelvic ultrasound, surgery and urology consults), colostomy with mucous fistula for complete faecal diversion, drain the vagina and divert the urinary tract as needed. Spinal ultrasound in the first 3 months — tethered cord in 40%. Definitive repair belongs in specialist centres.
  • Cloacal exstrophy: two hemibladders separated by an intestinal plate, with omphalocele and imperforate anus. Newborn surgery closes the omphalocele, repairs the bladder, and creates a vesicostomy and colostomy; sex assignment and long-term urological follow-up are part of care.

9. Monitoring

What to Track
  • Stooling pattern, distension, and signs of enterocolitis (even after pull-through).
  • Stoma function if a colostomy is present.
  • Growth, continence outcomes, and follow-up dilations after ARM repair.

10. Complications

Watch For
  • Hirschsprung-associated enterocolitis (can recur even after surgery) — life-threatening.
  • Anastomotic strictures; long-term constipation or incontinence.
  • ARM: continence and functional outcomes depend on the level and associated sacral/spinal anomalies.

11. Escalation & Follow-Up

Escalate When…
  • Suspected Hirschsprung enterocolitis (fever, distension, explosive diarrhea, sepsis).
  • High ARM or significant associated anomalies.
Follow-Up
  • Pediatric surgery for staged repair and continence follow-up.
  • Bowel-management programs; genetics for syndromic ARM/Hirschsprung.
Parent Counselling Points
  • "The nerves that make the bowel push stool are missing at the end of the gut, so we remove that segment. Sometimes we use a temporary stoma first."
  • "Watch for fever, a swollen tummy, and foul explosive diarrhea — that needs urgent care even after surgery."

12. Key Pearls

High-Value Clinical Pearls
  • ARM is a look-at-the-perineum diagnosis; Hirschsprung is a remember-to-suspect diagnosis (no meconium >48h).
  • Suction rectal biopsy (absent ganglion cells) is the gold standard for Hirschsprung.
  • Hirschsprung associates with Down syndrome; ARM with VACTERL.
  • Hirschsprung-associated enterocolitis is the life-threatening complication — treat urgently.
  • High ARM lesions usually need a colostomy before definitive PSARP.

13. Common Mistakes to Avoid

Pitfalls & Better Practice

The recurring errors in ARM and Hirschsprung.

MistakeWhy it harmsBetter practice
Skipping the perineal exam.Misses ARM.Inspect the anus at birth.
Ignoring delayed meconium.Misses Hirschsprung.Investigate if no meconium >48h.
Missing enterocolitis.Rapid sepsis and death.Decompress + antibiotics urgently.
Forgetting VACTERL in ARM.Misses cardiac/renal/spinal anomalies.Full associated-anomaly screen.

14. Board-Style High-Yield Summary

Key Takeaways
  • ARM: found on the perineal exam; classify low vs high; screen VACTERL; high lesions → colostomy then PSARP.
  • Hirschsprung: aganglionosis from the internal sphincter proximally; delayed meconium; associated with Down syndrome.
  • Diagnosis: suction rectal biopsy (gold standard); contrast enema shows transition zone.
  • Hirschsprung-associated enterocolitis is life-threatening — irrigations + antibiotics.
  • Definitive treatment: pull-through (Hirschsprung); PSARP (ARM).

15. References

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