Hirschsprung-Associated Enterocolitis

Hirschsprung associated enterocolitis is inflammation of the colon and distal small bowel in a child with Hirschsprung disease, occurring before or after surgery, and is the leading cause of death in the disease.

It develops in about 20 to 40% of children with Hirschsprung disease. Peak incidence is in the first 3 months after pull through surgery, but it can occur at any age.

Risk factors are Down syndrome, long segment or total colonic aganglionosis, delayed diagnosis, anastomotic stricture or leak, residual aganglionic or transition zone bowel, previous episode of enterocolitis and use of opioids or anticholinergic drugs.

Pathophysiology.

Functional distal obstruction from aganglionic bowel causes stasis, bacterial overgrowth and mucosal ischaemia from raised luminal pressure.

Changes in mucin, impaired mucosal barrier and altered microbiota allow bacterial translocation, leading to sepsis. Toxic megacolon and perforation follow in severe cases.

• Fever, abdominal distension, explosive foul smelling diarrhoea or paradoxical absence of stool, vomiting and lethargy.
• Rectal examination may release a gush of liquid, foul smelling stool and gas.
• Hypotension, tachycardia and poor perfusion in severe disease.

Red flags.

• Peritonism, absent bowel sounds or free air, indicating perforation.
• Rapid deterioration with hypotension and lactic acidosis, indicating septic shock.

• Clinical diagnosis supported by abdominal X-ray: dilated bowel loops, air fluid levels, a cut off sign, thickened bowel wall and pneumatosis in severe cases. Contrast enema is avoided in acute illness.
• Blood count (leucocytosis or leucopenia), CRP, blood gas, lactate, electrolytes and creatinine, and blood culture.
• Stool culture and testing for Clostridioides difficile toxin.

Differential diagnosis. Infective gastroenteritis, Clostridioides difficile colitis, necrotising enterocolitis in neonates, obstruction from stricture and sepsis from another source.

Resuscitation.

• Nil by mouth, nasogastric decompression and IV fluid boluses of 10 to 20 mL/kg 0.9% sodium chloride, repeated as perfusion needs.
• Correct acidosis, electrolytes and glucose.

Decompression. Rectal irrigation with warm 0.9% sodium chloride in 10 mL/kg aliquots through a large bore soft tube until returns are clear, repeated 2 to 3 times daily until improved.

Antibiotics. Broad spectrum cover for Gram negative organisms and anaerobes. For infants over 1 month: gentamicin 7 mg/kg IV once daily, metronidazole 7.5 mg/kg IV every 8 hours and ampicillin 50 mg/kg IV every 6 hours, with doses adjusted to renal function and gentamicin levels. In neonates, doses and intervals depend on gestation and postnatal age. Oral metronidazole 7.5 mg/kg every 8 hours may complete treatment once improved. Duration is usually 7 to 10 days.

Surgery. Laparotomy for perforation, or failure of medical treatment, with a stoma to decompress the bowel. Consider examining the pull through for stricture, twisting or retained aganglionic bowel when episodes recur.

Monitoring. Perfusion, urine output, abdominal girth, gases, lactate and inflammatory markers. Gentamicin levels before the third dose.

Referral and escalation. Early paediatric surgical review for all cases and intensive care referral for shock.

Special groups.

• Children with Down syndrome have a higher rate and higher mortality, so a lower threshold for admission and early treatment applies.
• After surgery, rectal washouts at home and early review for stricture reduce recurrence in those with repeated episodes.