[The enteric nervous system and interstitial cells of Cajal. Changes in chronic constipation in adults]

Intestinal innervation disorders are part of the broad etiological spectrum of chronic constipation and need to be specifically addressed in differential diagnosis. The enteric nervous system constitutes the largest peripheral nervous system of its own ("brain in the gut"), and is involved in the mediation of intestinal motility. Morphologically different nerve cell types aggregate into intramural plexus layers and release a multitude of neurotransmitters. Malformations or lesions of the enteric nervous system may lead to a severely prolonged intestinal transit time resulting in chronic constipation resistant to conservative treatment. In contrast to the early manifestation of aganglionosis, non-aganglionic or acquired alterations to the intramural nerve plexus often remain unrecognised up to adulthood. Histopathological diagnosis is carried out by enzyme or immunohistochemical staining, either on sections or whole mount preparations, allowing an optimal visualization of the nerve plexus architecture. To diagnose hypoganglionosis, enteric ganglionitis or alterations in interstitial cells of Cajal, full-thickness biopsies are required. Interstitial cells of Cajal contribute significantly to the mediation of intestinal motility by generating "slow wave" activity. In adult patients with slow-transit constipation and megacolon, the intramuscular networks of the interstitial cells of Cajal show a significantly reduced density.