Hirschsprung Disease

A 3 day old newborn presents with progressive abdominal distension, bilious vomiting, and failure to pass meconium within the first 48 hours of life. On examination, the abdomen is distended and rectal examination produces explosive discharge of stool and gas. Abdominal X-ray shows dilated bowel loops. Contrast enema demonstrates a transition zone between dilated proximal colon and narrow distal segment. Diagnosis?

Diagnosis is Hirschsprung disease.

1. Definition

Hirschsprung disease is a congenital aganglionic megacolon caused by absence of enteric ganglion cells in the distal intestine, leading to functional bowel obstruction.

It is classified as a neurocristopathy due to failure of neural crest cell migration into the bowel wall.

2. Pathophysiology

1. Failure of neural crest cell migration during embryogenesis
2. Absence of ganglion cells in:
• Meissner submucosal plexus
• Auerbach myenteric plexus
3. Affected bowel segment remains tonically contracted
4. Functional obstruction develops
5. Proximal bowel becomes dilated and hypertrophied due to fecal stasis

3. Epidemiology

1. Incidence approximately 1 in 5,000 live births
2. More common in males
3. Rectosigmoid colon is most commonly affected
4. Severity depends on length of aganglionic segment

Associated Conditions

1. Down syndrome (trisomy 21)
2. RET proto-oncogene mutations
3. MEN2A
4. Congenital central hypoventilation syndrome (Ondine syndrome)
5. Waardenburg syndrome

4. Classification

Short-Segment Disease

1. Most common form (~80%)
2. Usually limited to rectosigmoid colon
3. May present later with chronic constipation

Long-Segment Disease

1. Extends proximal to sigmoid colon
2. More severe neonatal obstruction

Total Colonic Aganglionosis

1. Rare
2. Severe neonatal intestinal obstruction
3. May show foreshortened “question mark” colon on contrast enema

5. Clinical Features

5.1 Neonatal Presentation

Classic features:

1. Failure to pass meconium within first 48 hours
2. Progressive abdominal distension
3. Bilious vomiting

Long-segment disease often presents with complete intestinal obstruction

5.2 Physical Examination

1. Distended abdomen
2. Empty rectum on digital rectal examination
3. Explosive passage of stool and flatus after rectal examination (“squirt sign”)

5.3 Infants and Older Children

May present with:

1. Chronic constipation
2. Failure to thrive
3. Abdominal distension
4. Feeding difficulties
5. Poor weight gain

Fecal soiling is uncommon

6. Hirschsprung-Associated Enterocolitis (HAEC)

A life-threatening complication that may occur preoperatively or postoperatively

Clinical features:

1. Fever
2. Abdominal distension
3. Explosive diarrhea or obstipation
4. Vomiting
5. Toxic megacolon
6. Sepsis

It is a major cause of morbidity and mortality

7. Diagnosis

7.1 Plain Abdominal X-Ray

Findings:

1. Dilated bowel loops
2. Air-fluid levels
3. Distal bowel obstruction

7.2 Contrast Enema (Water-Soluble)

Classic findings:

1. Narrow distal aganglionic segment
2. Dilated proximal ganglionated bowel
3. Transition zone between narrow distal bowel and dilated proximal colon
4. Rectosigmoid ratio <1

Important Points

1. Contrast enema may underestimate aganglionic segment length
2. Approximately 10% of neonates may lack classic radiologic findings
3. Clinical suspicion still warrants biopsy even if imaging is inconclusive

7.3 Anorectal Manometry

Finding:

1. Absence of rectoanal inhibitory reflex (RAIR)

Normally, rectal distension causes relaxation of the internal anal sphincter

Absent RAIR strongly suggests Hirschsprung disease but does not confirm diagnosis

7.4 Rectal Biopsy (Gold Standard)

Histopathology Findings

1. Absence of ganglion cells
2. Hypertrophied nerve trunks
3. Increased acetylcholinesterase staining
4. Absence of calretinin staining

Biopsy Techniques

Suction Rectal Biopsy

1. Preferred initial biopsy method in infants and neonates
2. Bedside procedure with low morbidity

Full-Thickness Biopsy

1. Used in older children
2. Used when suction biopsy is inadequate

Biopsy should be obtained at least 1 cm above the dentate line and include mucosa and submucosa

8. Differential Diagnosis

1. Meconium ileus
2. Small left colon syndrome
3. Intestinal atresia
4. Functional constipation
5. Hypothyroidism
6. Anorectal malformations

9. Management

9.1 Initial Stabilization

1. IV fluids
2. Nasogastric decompression
3. Rectal irrigations
4. NPO if severe obstruction present
5. Broad-spectrum antibiotics if enterocolitis suspected

Families should be educated regarding rectal irrigations and enterocolitis prevention

9.2 Definitive Surgical Management

Principles

1. Identify extent of aganglionosis
2. Resect aganglionic bowel
3. Pull normally ganglionated bowel through to anus
4. Restore bowel continuity

Surgical Procedures

Swenson Procedure

1. Full-thickness resection of aganglionic bowel
2. Primary coloanal anastomosis

Advantage:

• Minimal residual aganglionic bowel

Risk:

• Pelvic nerve or urethral injury

Soave Procedure

1. Endorectal pull-through preserving muscular cuff

Advantage:

• Less pelvic dissection

Complication:

• Muscular cuff may cause outlet obstruction

Duhamel Procedure

1. Retrorectal pull-through with stapled anastomosis

Advantage:

• Less pelvic dissection

Complication:

• Spur formation and constipation

10. Postoperative Complications

Early Complications

1. Anastomotic leak
2. Enterocolitis
3. Perianal excoriation

Late Complications

1. Persistent constipation
2. Functional obstruction
3. Anastomotic stricture
4. Fecal incontinence
5. Residual aganglionosis

Persistent symptoms require evaluation for:

1. Anatomic causes
2. Functional causes
3. Residual aganglionosis

11. Prognosis

1. Most children improve significantly after surgery
2. Rectosigmoid disease generally has good long-term continence outcomes
3. Early recognition and aggressive management of enterocolitis improve prognosis

12. Key Clinical Insight

Newborn with delayed passage of meconium, abdominal distension, bilious vomiting, and explosive stool after rectal examination strongly suggests Hirschsprung disease

13. Key Exam Points

1. Hirschsprung disease results from failure of neural crest cell migration
2. Aganglionosis involves Meissner and Auerbach plexuses
3. Rectosigmoid colon is most commonly affected
4. Failure to pass meconium within first 48 hours is a major red flag
5. Explosive stool after rectal examination is characteristic
6. Contrast enema shows transition zone with rectosigmoid ratio <1
7. Absence of rectoanal inhibitory reflex supports diagnosis
8. Rectal biopsy is the gold standard diagnostic test
9. Hirschsprung disease is associated with Down syndrome and RET mutations
10. Definitive treatment is surgical pull-through procedure