Asymmetrical nature of the muscular anatomy of the infantile pylorus: a possible consideration in pyloromyotomy.

Post-mortem studies of the normal infantile pylorus have demonstrated an asymmetrical structure with the mucosa protruding under the circular muscle at the lesser curve but not on the anterior surface. In addition the circular muscle was often discontinuous at the pyloroduodenal junction with only longitudinal fibres or even fibrous tissue separating the mucosa from the serosa. In a further specimen in which a pyloromyotomy had been performed 10 weeks previously, this asymmetry was more pronounced. This anatomy suggests that in pyloric stenosis it may be safer to site the caudal part of the pyloromyotomy incision on the anterior surface, rather than on the anterosuperior surface as most authors recommend. Perforation of the mucosa is predicted to be less likely.