Total colonic aganglionosis and Hirschsprung's disease: shades of the same or different?

Total colonic aganglionosis is a relatively uncommon form of Hirschsprung's disease (HSCR) occurring in approximately 2-13% of cases. It can probably be divided into total colonic aganglionosis (TCA; defined as aganglionosis extending from the anus to at least the ileocaecal valve, but no more than 50 cm proximal to the ileocaecal valve) and total colonic and small bowel aganglionosis, which may involve a very long segment of aganglionosis. Clinically, they appear to represent a different spectrum of disease in terms of presentation and difficulties in diagnosis which may be experienced, suggesting a different pathophysiology from the more common forms of HSCR. It is not yet clear whether TCA merely represents a long form of HSCR or a different expression of the disease. There are a number of differences between TCA and other forms of HSCR, which require an explanation if its ubiquitous clinical features are to be understood. There is some evidence suggesting that instead of being purely congenital, it may represent certain different pathophysiologic mechanisms, some of which may continue to be active after birth. This study reviews all that is known about the clinical, radiological and histopathologic differences between TCA and the more frequently encountered recto-sigmoid (or short-segment) and correlates them with what is currently known about the genetic and molecular biologic background to find possible pathogenetic mechanisms.