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Hirschsprung disease is a congenital disorder characterized by the absence of ganglion cells in the distal colon, resulting in functional intestinal obstruction. It typically presents in newborns with failure to pass meconium, abdominal distension, and chronic constipation, though milder cases may present later in childhood.
The condition results from failed migration of neural crest cells during embryonic development, leading to aganglionosis in the affected bowel segment. Without enteric ganglia, the affected segment cannot relax and remains in a state of tonic contraction, creating a functional obstruction that prevents normal peristalsis and bowel evacuation.
Diagnosis is suspected in newborns who fail to pass meconium within 48 hours or present with signs of intestinal obstruction. Rectal biopsy showing absence of ganglion cells and presence of hypertrophied nerve fibers confirms the diagnosis, while contrast enema may show the transition zone between normal and aganglionic bowel.
Key imaging focus: Transition zone, rectosigmoid ratio reversal, delayed evacuation at 24h