Investigation

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 Infants with Hirschsprung's disease usually will fail to pass meconium in the first 24 h of life, although this history is often difficult to obtain. Barium enema may be unreliable in diagnosing Hirschsprung's disease in the newborn infant because the colon is not dilated enough to show a transition zone. In older infants and children, barium enema will show the size difference between the dilated ganglionic colon and the distal constricted aganglionic rectal segment. The barium enema in total colonic aganglionous usually shows a markedly shortened colon.
 Rectal biopsy makes the definitive diagnosis of Hirschsprung's disease. Suction rectal biopsy provides a small piece of mucosa and submucosa without the requirement for anesthesia. Occasionally the suction biopsy is not diagnostic and a full-thickness biopsy is required. The histopathology of Hirschsprung's disease is the absence of ganglion cells in the myenteric plexuses, increased staining of a cholinesterase stain and the presence of hypertrophied nerve bundles. Some surgeons have found the use of rectal manometry helpful, particularly in older children, but it is not as accurate a diagnostic tool as is rectal biopsy. Some centers employ manometry, histochemical studies or special stains for diagnosis. These special studies are only as good as the person performing them and interpreting the results