Chronic idiopathic intestinal pseudo-obstruction caused by a degenerative disorder of the myenteric plexus: the use of Smith's method to define the neuropathology.

In this paper we report the pathologic basis of chronic idiopathic intestinal pseudo-obstruction in a patient who had a subtotal colectomy and ileorectal anastomosis for severe obstipation. Conventional light microscopy of the resected intestine showed an increased thickness of the longitudinal muscle, minimal amounts of smooth muscle fibrosis, and normal smooth muscle cells. The morphology of the myenteric plexus was difficult to interpret with this technique, but quantification of colonic neurons revealed a significantly decreased number compared with controls. Silver stains of the myenteric plexus by Smith's method showed: (a) patchy loss of nerve tracts with replacement by Schwann cells, (b) degeneration and decreased numbers of both argryophilic and argyrophobic neurons, (c) fragmentation and dropout of many axons, and (d) increased thickness and disorganized spatial arrangement of other axons. The pathology of this intestinal neuropathy could be missed by conventional light microscopy and may be apparent only when a silver technique is used to visualize the myenteric plexus.