Makindo Medical Notes

A normal barium enema does not exclude Hirschsprung's disease. Up to 90% of infants with Hirschsprung's disease fail to pass meconium in the first 24 hours of life.

About

• Hirschsprung's Disease is a congenital condition characterized by the absence of myenteric ganglion cells in the distal bowel wall, leading to functional bowel obstruction.
• Also known as congenital megacolon, it affects approximately 1 in 5000 live births.

Associations

• Family history of Hirschsprung's disease
• Genetic Conditions: Neurofibromatosis, Down syndrome, Waardenburg's syndrome, Multiple endocrine neoplasia, type IIA
• Congenital Anomalies: Ventricular septal defect (VSD), renal agenesis

Pathology

• Hirschsprung's disease results from the failure of neural crest cells to migrate to the distal bowel during fetal development.
• The absence of parasympathetic ganglion cells in the myenteric (Auerbach's) plexus leads to failure of bowel relaxation, causing functional obstruction.
• Due to the lack of peristalsis, the aganglionic segment remains constricted, and the proximal bowel becomes dilated and hypertrophic, leading to megacolon.

Aetiology

• About 70% of cases involve the rectosigmoid colon, 20% involve the entire colon, and 10% may extend into the small intestine.
• The aganglionic bowel lacks peristalsis and passively constricts, creating a mechanical obstruction.

Clinical Features

• Infants typically appear healthy at birth but then fail to pass meconium within the first 24-48 hours of life.
• Symptoms include abdominal distension, bloating, vomiting, poor feeding, and progressive constipation.
• Milder cases may present later in infancy or childhood with chronic constipation.
• Hirschsprung's Enterocolitis: A serious complication, characterized by severe distension, fever, and diarrhoea, and can be life-threatening if not treated promptly.

Differential Diagnoses

• Functional constipation
• Meconium ileus (associated with cystic fibrosis)
• Imperforate anus
• Neonatal sepsis
• Intestinal atresia

Investigations

• Rectoanal Manometry: Balloon distension of the rectum fails to trigger internal anal sphincter relaxation, indicative of Hirschsprung's disease.
• Contrast Enema: May show a transition zone between the narrow aganglionic segment and the dilated proximal colon. However, a normal enema does not exclude the diagnosis.
• Rectal Biopsy: The definitive diagnostic test, showing the absence of ganglion cells and the presence of hypertrophic nerve trunks. The biopsy should be taken at least 1.5 cm above the dentate line, as the distal rectum naturally lacks ganglion cells.

Management

• Initial Management: If enterocolitis or other serious symptoms develop, perform a colostomy in healthy bowel to stabilize the patient until definitive surgery can be performed.
• Bowel Decompression: Serial rectal irrigations may be used before surgery to decompress the bowel and prevent enterocolitis.
• Surgical Intervention: Swenson's procedure is the classic surgery, where the aganglionic segment of the rectum is resected, and the healthy ganglionated colon is pulled through and connected to the anus.
• Long-term Management: Post-surgery, bowel function may remain imperfect for several years, and some children may experience constipation or incontinence. Regular follow-up is necessary to monitor bowel function and address complications.

References

• Hirschsprung's Disease: Diagnosis and Management