Normal aspects of colorectal motility and abnormalities in slow transit constipation

Abstract

Human colonic motility is a relatively difficult topic to investigate. However, the refinement of manometric techniques in recent years enabled us to study both the proximal and distal segments of the viscus. The present paper reviews our knowledge about normal aspects of colorectal motility in man and the abnormalities found in slow transit constipation (STC), one of the most frequent and difficult to treat subtypes of constipation. An internet-based search strategy of the Medline and Science Citation Index was performed using the keywords colon, colonic, colorectal, constipation, slow transit, motility, rectal, rectum in various combinations with the Boolean operators AND, OR and NOT. Only articles related to human studies were used, and manual cross-referencing was also performed. Most of colonic motor activity is represented by single nonpropagated contractions, rarely organized in bursts; this activity is maximal during the day, especially after waking and following meals. In addition, a specialized propagated activity with propulsive features is detectable, represented by high- and low-amplitude propagated contractions. In the severe form of constipation represented by the slow transit type, the above motor activity is completely deranged. In fact, both basal segmental activity (especially in response to meals) and propagated activity (especially that of high amplitude) are usually decreased, and this may represent a physiologic marker of this disorder. Human colonic motor activity is quite a complex issue, still only partly understood and investigated, due to anatomic and physiological difficulties. In recent years, however, some more data have been obtained, even in proximal segments. These data have helped in elucidating, although only in part, some pathophysiological mechanisms of chronic constipation, and especially of the STC subtype.

Figure 1

Representative manometric tracing of normal colonic segmental activity. Note that most contractions feature low amplitude, with sporadic ones (arrow) exceeding 50 mmHg. Recording points are 12 cm apart, and span from the transverse colon (T) to the rectum (R).

Figure 2

Representative manometric tracing showing a LAPC (arrow). Note also, in the last tracing, the presence of a burst of segmental sigmoid activity (asterisk). Recording points are 12 cm apart, and span from the transverse (T) to the sigmoid colon (S).

Figure 3

Representative manometric tracing of a HAPC. Note that the amplitude of the propagated sequence is well distinct with respect to the background segmental activity. Recording points are 12 cm apart, and span from the distal transverse (T) to the proximal sigmoid colon (S).

Figure 4

Representative manometric tracing showing two episodes of periodic colonic motor activity (asterisks) occurring independently at different colonic levels (proximal descending colon and rectosigmoid junction, respectively). Recording points are 12 cm apart, and span from the transverse colon (T) to the rectum (R).

Figure 5

Colonic motor response to eating in normal subjects. All post-meal values (asterisk) are significantly (^aP<0.05) different with respect to basal values in both proximal (A/T) and distal (D/S) segments. MI, motility index.

Figure 6

Percentage and distribution of HAPC/24 h in control subjects and severely constipated patients. M, meal, A, awakening. Adapted from Ref.[65].