Immature intrinsic nerve innervations of pyloric muscle in idiopathic hypertrophic pyloric stenosis.

BACKGROUND AND PURPOSE: Various etiologies have been suggested to be responsible for the development of idiopathic hypertrophic pyloric stenosis (IHPS) in the newborn. The purpose of this study was to determine the maturity of intrinsic nerves and nitrergic neurons in the pyloric muscle in IHPS. METHODS: Full thickness pyloric muscle specimens were obtained from 6 infants with IHPS with age ranging from 27 to 95 (mean 58) days old and subjected to immunohistochemical and double chemiluminescence staining for protein gene product 9.5 (PGP9.5) and neuronal nitric oxide synthase (nNOS). RESULTS: The results showed absence of myenteric plexus between the circular and longitudinal muscle layers in 2 patients, decrease in 1 patient, normal myenteric plexus in 1 patient, and absence of nNOS-containing neurons in 4 patients. All 6 patients had expression of markers for supporting nerve cells and myogenesis in the pyloric smooth muscle. CONCLUSIONS: These results suggest that absence or immaturity of intrinsic nerve and nNOS-containing neurons in the pyloric muscle is the cause of IHPS. The demonstrated lack of innervation or delayed innervation may be the responsible mechanism for the development of IHPS, but further study is needed to elucidate the pathogenesis.