HUMAN COLONIC MOTILITY - PHYSIOLOGICAL-ASPECTS

From the point of view of its motor activity, the human colon is probably the least understood of the abdominal hollow viscera. This is due to several facts: a) its proximal portions are relatively inaccessible due to anatomical reasons; b) there is no reliable animal model due to the considerable anatomic-physiological differences among mammals. For instance, most deductions about human colonic motor activity have been drawn from experiences in cats and dogs, in which the colon displays a cecum which is almost atrophic, and the viscus is featureless and C-shaped, without the haustrations and the sharp angulations seen in man [1], c) the wide fluctuations of motility in the daily time course of the same individual makes the interpretation of many studies difficult [2, 3, 4], especially considering the fact that, until recently, most of the studies on human colonic motility have been conducted for relatively short (30-180 min) recording periods [5]. Recently, however, techniques that allow recording from the proximal portions of the human colon have been developed, and prolonged (24 h or more) observations of myoelectrical and contractile events have been achieved, thus improving our knowledge of the normal physiologic properties of the viscus [6, 7]. These informations have furthermore been integrated and confirmed by scintigraphic techniques (less invasive), that allow the measurement of intracolonic flow activity [8, 9]. The purpose of the present paper is to review the physiological aspects of colonic motility in man, quoting animal studies where human ones are lacking. We will briefly introduce some basic concepts, then a more detailed description of the main topic will follow.