Intermittent rectal motor activity: a rectal motor complex?

Prolonged nocturnal recordings from multiple sites in the anorectum and duodenum were performed in 12 healthy volunteers to investigate the presence and determine the characteristics of nocturnal rectal motor activity and assess any synchronicity with phase III of the small intestinal migrating motor complex. Runs of phasic contractions of two contractile frequencies (3 or 6/minute), sustained for more than three minutes, and preceded and followed by motor quiescence were observed in 10 of the 12 subjects. This phenomenon is similar to that described by other investigators and termed the 'rectal motor complex'. The runs of contractions showed considerable inter- and intrasubject variation, with a duration of 3-30 minutes (median 9.0), amplitude of 10-55 mm Hg (median 20.0), and periods of 10-420 minutes (median 55.5) between contractile activity. There was no propagation through the rectum, the phasic motor activity rarely occurred simultaneously at more than one rectal recording site. No consistent relation with phase III of the small intestinal migrating motor complex was observed in any subject. In view of these findings, we question whether this intermittent motor activity merits the term 'rectal motor complex'.