Pathogenesis of infantile hypertrophic pyloric stenosis: recent progress.

Although infantile hypertrophic pyloric stenosis (IHPS) is the most common condition requiring surgery in the first few months of life, its pathogenesis is not fully understood. Reviews of the recent progress in the pathogenesis of IHPS show: (1) there is increasing evidence to suggest that smooth-muscle cells in IHPS are not properly innervated; (2) because non-adrenergic, non-cholinergic nerves are mediators of smooth-muscle relaxation, it is likely that the absence of these nerves in pyloric muscle is the cause of excessively contracted hypertrophic circular pyloric muscle; (3) there are abnormal amounts of extracellular matrix proteins in hypertrophic pyloric muscle. Circular muscle cells in IHPS are actively synthesizing collagen, and this may be responsible for the characteristic "firm" nature of the pyloric tumor; and (4) the increased expression of insulin-like growth factor-I, transforming growth factor-beta 1, and platelet-derived growth factor-BB and their receptors in hypertrophic pyloric muscle suggests that increased local synthesis of growth factors may play an important role in smooth-muscle hypertrophy in IHPS.