Clinical features

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 The presentation may be much subtle, with constipation and abdominal distention as the chief findings. Symptoms usually begin at birth, frequently with delayed passage of meconium. Any newborn who fails to pass meconium in the first 24-48 hours of life should be evaluated for possible Hirschsprung's disease. In some infants, the presentation is that of complete intestinal obstruction. Others have relatively few symptoms until several weeks of age, when the classic symptom of
 constipation has its onset. Diarrhea is not uncommon but differs from the usual infantile diarrhea in that it is associated with abdominal distension. Occasionally the patient will go many years with mild constipation and diagnosis will be delayed. Occasionally failure to thrive is the initial sign.
 The diagnosis is first suspected based on history and physical examinations (characteristically there is no stool in rectum and abdominal distension is painless).