Hirschsprung Disease
Hirschsprung disease (HD) is a congenital condition and a common cause of neonatal intestinal obstruction. It is a disorder of bowel motility caused by the absence of ganglion cells in a segment of the distal bowel. This aganglionic segment cannot relax, leading to a functional obstruction. The disease is more common in boys and has a higher incidence in children with certain genetic syndromes, most notably Down syndrome.
Pathophysiology
Hirschsprung disease results from a failure of neural crest cells to migrate down the gastrointestinal tract during embryonic development. This leads to a variable length of the distal bowel lacking the nerve plexuses (Auerbach and Meissner) that are essential for peristalsis. The normal, ganglionated bowel proximal to the affected segment works overtime to push contents through the tight, non-peristalsing section, causing massive dilation and hypertrophy.
Clinical Presentation
The presentation varies with the length of the affected bowel segment and the age of the child.
Neonates: The classic sign is a failure to pass meconium within the first 24-48 hours of life. Other obstructive symptoms include bilious vomiting and progressive abdominal distension.
Infants and Toddlers: If the affected segment is short, the diagnosis may be delayed. These children typically present with a history of severe, chronic constipation that is refractory to standard laxative therapy. They may also have poor feeding and faltering growth.
Complications: The most feared complication is Hirschsprung-associated enterocolitis, a life-threatening inflammation of the bowel that can lead to perforation and sepsis.
Diagnosis
The diagnosis is made through a combination of imaging and definitive histological studies.
Abdominal X-ray: This is a useful initial screening tool that may show dilated loops of bowel and a lack of gas in the rectum.
Barium Enema: This can demonstrate a transition zone—the classic finding of a narrow, aganglionic distal segment transitioning to a dilated, ganglionated proximal segment.
Anorectal Manometry: This test measures the function of the anal sphincters. In HD, the rectoanal inhibitory reflex is absent, which is highly suggestive of the disease.
Rectal Suction Biopsy: This is the gold standard for diagnosis. A small biopsy of the rectal mucosa is taken, and the absence of ganglion cells confirms the diagnosis.
Management
The definitive management for Hirschsprung disease is surgical.
Stabilisation: In the acute setting, the child’s condition must first be stabilised, which may involve fluid resuscitation and antibiotics if there is a concern for enterocolitis.
Surgical Resection: The aganglionic segment of the bowel is surgically resected, and the normal, ganglionated bowel is then pulled down and anastomosed to the anus. This procedure can be done as a single-stage operation or in multiple stages, with a temporary colostomy created to decompress the bowel.
Post-Operative Care: Prognosis for long-term bowel control is generally excellent after surgery, though some children may have issues with constipation or soiling that require medical management. Regular follow-up with a paediatric surgeon and gastroenterologist is crucial.