Hirschsprung's Disease

Hirschsprung's: Intro & Pathophysiology - Gut's Nerve Nap

• Pathophysiology: Congenital aganglionosis of distal gut.
  • Due to failed neural crest cell migration (neuroblasts) to hindgut.
  • Arrest occurs during 5th-12th weeks gestation.
  • Progression: Craniocaudal (distal to proximal).
• Key Features:
  • Rectum always involved.
  • Leads to functional obstruction; affected segment remains tonically contracted.
  • 📌 Mnemonic: 'HIrschsprung = HIgh up the colon involvement is less common' (short segment more common).

⭐ The aganglionosis in Hirschsprung's disease always involves the rectum and extends proximally for a variable distance.

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Hirschsprung's: Clinical Features - The Poop Stoppage

• Neonatal Onset (Most Common):
  • Delayed meconium passage: No stool within 24-48 hours post-birth.
  • Bilious (green) emesis.
  • Progressive abdominal distension.
  • Feeding refusal or intolerance.
  • Tight anal sphincter; explosive stool/gas on DRE (digital rectal exam) ("squirt sign" - suggestive).
• Later Presentation (Infancy/Childhood):
  • Chronic, intractable constipation (often since birth).
  • Foul-smelling, "ribbon-like" or pellet-like stools.
  • Marked abdominal distension, sometimes with visible peristalsis.
  • Failure to thrive (FTT); malnutrition.
  • ⚠️ Hirschsprung-Associated Enterocolitis (HAEC): fever, explosive diarrhea, distension, sepsis risk.

⭐ Failure to pass meconium in the first 24-48 hours of life is a cardinal sign of Hirschsprung's disease in a full-term infant.

Hirschsprung's: Diagnosis - Finding the Freeze

• Initial Imaging:
  • Abdominal X-ray (AXR): Suggestive findings include dilated proximal bowel loops, paucity of gas distally.
  • Contrast Enema (Barium/water-soluble): Crucial for identifying the transition zone (narrowed aganglionic segment, dilated ganglionic proximal colon). Retention of contrast > 24 hours is highly suggestive.
    • 📌 "Transition Zone = Trouble Zone"
• Functional Test:
  • Anorectal Manometry: Demonstrates absence of the Rectoanal Inhibitory Reflex (RAIR). Especially useful in older children; less reliable in neonates.
• Gold Standard Confirmation:
  • Rectal Suction Biopsy: Shows absence of ganglion cells in the submucosa. Increased acetylcholinesterase staining in nerve fibers is characteristic.

    ⭐ Full-thickness rectal biopsy (shows absent ganglion cells in submucosal & myenteric plexuses) is the gold standard.

  • Full-thickness biopsy if suction biopsy is inconclusive or for atypical cases.

Hirschsprung's: Management - Rerouting the Gut

• Initial:
  • Decompression: Rectal irrigation, NG tube.
  • IV fluids, antibiotics.
  • Nutritional support.
• Surgical:
  • Goal: Resect aganglionic bowel, pull-through ganglionic segment to anus.
  • Single-stage pull-through vs. Staged (colostomy, then pull-through).
• Procedures:
  • Swenson: Resection, end-to-end anastomosis.
  • Soave: Endorectal mucosectomy, pull-through.
  • Duhamel: Retrorectal pull-through.
• Complications:
  • Hirschsprung-Associated Enterocolitis (HAEC).

    ⭐ Hirschsprung-Associated Enterocolitis (HAEC) is the most common and life-threatening complication, even post-surgery.

  • Anastomotic leak/stricture.
  • Incontinence, obstructive symptoms.

Hirschsprung's: Genetics & Syndromes - Family Ties & Woes

• Key Genetic Loci:
  • RET proto-oncogene: Most common; mutations often in familial & long-segment HSCR.
  • EDNRB & EDN3: Endothelin-B receptor pathway genes.
• Associated Syndromes (Increased Risk):
  • Down syndrome (Trisomy 21)
  • Waardenburg syndrome (Type IV)
  • MEN 2A/2B (RET mutations)
  • Mowat-Wilson syndrome (ZEB2)

⭐ Mutations in the RET proto-oncogene are the most frequently identified genetic cause of Hirschsprung's disease.

High‑Yield Points - ⚡ Biggest Takeaways

• Congenital aganglionosis of the distal bowel, primarily due to failed neural crest cell migration.
• Most commonly affects the rectosigmoid colon (short-segment disease).
• Key presentation: Failure to pass meconium within 24-48 hours, bilious vomiting, and abdominal distension.
• Gold standard for diagnosis: Rectal suction biopsy demonstrating the absence of ganglion cells.
• Barium enema often shows a transition zone between a narrowed aganglionic segment and a dilated proximal bowel.
• Strong association with Down syndrome (Trisomy 21).
• Definitive treatment involves surgical resection of the aganglionic segment; monitor for Hirschsprung-Associated Enterocolitis (HAEC) post-operatively.