Hypertrophic pyloric stenosis: ultrastructural abnormalities of enteric nerves and the interstitial cells of Cajal.

Dysfunction of pyloric inhibition has been implicated in the pathophysiology of hypertrophic pyloric stenosis. Normal inhibition likely is mediated by peptidergic enteric nerves and also may involve interstitial cells of Cajal (ICC). The authors used electron microscopy to qualitatively assess these structures in infants with pyloric stenosis and in normal controls. Pyloric muscle strips from five infants with hypertrophic pyloric stenosis, from three normal pediatric organ donors, and from three adults were examined. The following observations were made. (1) Muscle cells were primarily in a proliferative phase in pyloric stenosis and exhibited very few gap junctions between smooth muscle cells or ICC compared with the control specimens. (2) The circular muscle layer in pyloric stenosis was characterized by near absence of large granular vesicle-containing nerve fibers compared with the control specimens. (3) There were fewer nerve cell bodies in the myenteric plexus in pyloric stenosis, and the total number of ganglia was lower than that in control samples. (4) Interstitial cells of Cajal were almost completely absent in patients with hypertrophic pyloric stenosis, but there was a group of cells resembling ICC that was termed ICC-like cells. These cells may represent a failure or delay in the maturation process of the ICC. These findings show that there are significant structural abnormalities of the inhibitory nervous system in hypertrophic pyloric stenosis. The ontogenic origins and functional significance of these results require further investigation.