High Amplitude Pressure Waves (HAPWs) are the only motor pattern routinely assessed in human colonic manometry. High-Resolution Colonic Manometry is able to provide more information and shows HAPW associated motor patterns that may have clinical relevance. Our aim was to characterize the HAPW associated rhythmic motor pattern, its myogenic basis based on its frequency pattern, its physiological significance and its potential diagnostic value. High-resolution manometry was performed using an 84 sensor water-perfused catheter in 7 healthy subjects. Pressures were recorded at baseline, after a meal, in response to balloon distension and bisacodyl administration. The most consistent motor pattern that followed HAPWs in healthy adults was a characteristic rhythmic motor pattern with distinct frequency components of 6, 9,12 and 15 cpm, clearly distinguishable from the breathing frequency. This pattern had an average duration of 78.1 ± 49.6 s (24 to 165), occurring over a section of the colon of 11.5 ± 5.9 cm (6 to18) length, which is about 2 or 3 haustra. The motor pattern ended 24.0 ± 7.0 cm above the anal verge; hence it is a characteristic of the sigmoid colon. Individual pressure transients within the pattern occurred almost exclusively instantaneous. To quantify, HAPWs were evoked by balloon distention, a 1000 kcal meal, and 10 mg luminal bisacodyl. Using balloon distention, 31 HAPWs were evoked, 16.1% were followed by quiescence and 48.4% by the rhythmic motor pattern; other HAPWs were associated with spontaneous pressure waves without the occurrence of this rhythmic motor pattern. In response to a meal, 30 HAPWs were evoked, 10.0 % were followed by quiescence and 33.3 % by the rhythmic motor pattern. In response to bisacodyl, 39 HAPWs were evoked, 5.1 % were followed by quiescence and 46.2 % by the rhythmic motor pattern. This motor pattern also occurred independently of the HAPWs with dominant frequencies of 3 and 6 cpm at baseline condition, indicating the motor pattern was in a less excited state with more retrograde propagation. A rhythmic motor pattern characteristically follows the HAPW in the sigmoid colon. Its occurrence after an HAPW suggests that this rhythmic motor pattern shares neural excitation with the HAPWs. Its frequency spectrum (3,6,9,12,15 cpm) and very fast propagation (or instantaneous appearance) suggest orchestration by a network of interstitial cells of Cajal (ICC). The frequency spectrum is identical to that in previous electrical recordings of the human colon (2). The occurrence of this motor pattern in healthy adults suggests that it may not be a biomarker of constipation in adults (1) and suggests that it may be a signature of intrinsic ICC activity. 1. Giorgio et al. Neurogastr. Mot. 2013. 2. Sarna et al. Gastroenterology 1981. High-Resolution Colonic Manometry: a High Amplitude Pressure Wave is followed by a Rhythmic Motor Pattern in the distal colon. CIHRHamilton Academic Health Sciences Organization