Parallel diversions of the gastrointestinal tract: Flow-mechanic consideration with congenital and acquired case reports

Using the analogy of a fluid carrying system of pipes, the mechanisms by which the conversion of the "in series" interconnection of the different parts of the gastrointestinal tract into a "parallel" network is seen as the multiplication of the channelling of the gut, and the change in the direction of flow of the contents of the tract which come about by the introduction of junctional points into the system. The multiplication of the channel can also produce extra discharge points in the form of internal and external gastrointestinal fistulas, apart from the initial single discharge point, the anus. The interconnection of the initial network with an additional discharge channel short circuits and can overload the initial network. Clinically, this can present as a stagnation or an intestinal obstruction. With chronic dilatation of the large intestine, the overload can mimic a megacolon or a Hirschsprung's disease. The short circuiting can also by-pass secretory, digestive and absorptive intestinal surfaces to lead to a malabsorption syndrome. The clinical picture of the diversions are illustrated by physiological and pathophysiological as well as curative case examples.