Characterization of anal slow waves and ultraslow waves in patients with constipation and healthy subjects

Background: Anal slow waves (SW) and ultraslow waves (USW) have been documented previously, yet their significance remains uncertain. Our aims were to characterize the prevalence and features of SW and USW in healthy subjects and patients with constipation and to correlate them with clinical features and anorectal physiological testing. Methods: Forty-three healthy female subjects and 83 female tertiary referral patients with constipation were included. High-resolution water-perfused manometry was performed. Retrospective blinded descriptive and quantitative analyses of manometric tracings were completed with a focus on SW and USW. Key Results: SW were present in 58% of healthy subjects and 62% of constipated patients (p = 0.72) yet USW were seen almost exclusively in constipated patients (27% vs. 2% health; p < 0.0001). Frequencies and mean amplitudes of SW and USW were similar in both groups. Anal resting and squeeze pressures were higher in patients with SW compared to those without (p < 0.001, p = 0.004, respectively). Patients with USW had higher anal resting pressure and shorter duration of sustained squeeze compared to those without (p < 0.001 for both). There was a trend for less obstetric injury in constipated patients with USW compared to those without (23% vs. 48%; p = 0.05). Conclusions and Interferences: While SW were common in both constipated and healthy subjects, USW were almost exclusively observed in constipated patients. Some correlations were observed with other anorectal physiology parameters such as high resting anal pressure with both SW and USW. Formal definitions for SW and USW are proposed. Further research into the clinical significance of these waves is warranted.