A quantitative study of the morphological and histochemical changes within the nerves and muscle in infantile hypertrophic pyloric stenosis

Purpose: The aim of this study was to quantify changes in dimensions of nerves and muscle and the proportionate expression of neural antigens in infantile hypertrophic pyloric stenosis (IHPS). Methods: Twenty specimens of pylorus from children with IHPS and age/sex-matched controls were examined using conventional histology and immunohistochemistry for a range of nerve and muscle antigens. The changes in the proportion of nerves expressing each antigen were quantified and statistically analyzed. Results: The longitudinal muscle was found to be hypertrophic and protein gene product 9.5-stained nerves appeared longer and thicker in the myenteric plexus and shorter in the longitudinal muscle layer in IHPS. The proportion of nerves that expressed neural nitric oxide synthase (nNOS) was found to be diminished in all the IHPS tissues examined. In the circular muscle and myenteric plexus, the proportion of nerves that expressed vasoactive intestinal polypeptide (VIP) and nNOS was almost identically diminished. The expression of calcitonin gene-related polypeptide and substance P was proportionately reduced in the myenteric plexus. Conclusions: The results of this study represent the first quantitative analysis of nerves and muscle in IHPS. The muscle hypertrophy is not restricted to circular muscle layer. The changes in nerve morphology cannot be attributed to a dilutional effect of the muscle hypertrophy. The selective changes in nerve and ganglion morphology varies between tissue layers and neural antigen expressed. The findings of reduced proportions of nerves expressing, in particular, nNOS may shed some light on the etiology of this condition. Copyright (C) 1998 by W.B. Saunders Company.