[Disorders of intestinal innervation as a possible cause for chronic constipation]

The gastrointestinal tract contains the largest amount of nerve cells apart from the central nervous system constituting together with glial cells the enteric nervous system (ENS). The morphology of the ENS is characterized by intramurally located ganglionated and non-ganglionated plexus of different structure. The diversity of neurotransmitters synthesized by the different nerve cell types as well as the complex neuronal circuits establish the basis for the mediation of a coordinated intestinal motility. Subsequently abnormalities of the ENS may cause severe constipation. The most acknowledged intestinal innervation disorder represents aganglionosis (Hirschsprung's disease) characterized by the absence of intramural nerve cells and the hypertrophy of nerve fiber bundles within the affected intestinal segment. Non-aganglionic intestinal innervation disorders include intestinal neuronal dysplasia (IND), hypoganglionosis and heterotopic ganglia. The pathogenesis of intestinal neuronal malformations is mainly attributed to development disorders of the ENS, in part caused by genetic defects. Furthermore, the ENS can sustain damage during the postnatal period by ischemic, inflammatory, autoimmunological processes or neurotoxic agents. The histopathological diagnosis of intestinal innervation disorders is achieved by enzyme- and immunohistochemical methods. The examination of the ENS can be carried out on mucosal, deep submucosal or full-thickness biopsies using serial transverse sections as well as on intestinal whole-mount preparations allowing a three-dimensional demonstration and assessment of the intramural plexus. Structural abnormalities of the myenteric and submucosal plexus and an abnormal content of neurotransmitters have been considered to be responsible for primary chronic constipation. However, until now no unified pathophysiological concept has been established due to the partly contradictory findings. Therefore, an important goal in patients with chronic constipation should be a detailed quantitative and qualitative assessment of the underlying neurohistopathology. The correlation of these data with functional parameters of intestinal motility may represent an useful tool for the differential diagnostic and therapeutic considerations.