Stimulation of Reflexes in the Gastrointestinal Tract
Utilization of the preserved gastrointestinal reflexes can be beneficial in bowel management following SCI. The gastro-colic reflex is stimulated by gastric distention due to eating and can activate bowel motility and promote defecation (Sloots et al. 2003; Ford et al. 1995). Digital stimulation of anorectal reflexes has been shown to result in increased rectal contractions and could be useful in bowel evacuation following SCI (Shafik et al. 2000).
Discussion
Digital rectal stimulation (DRS) is often used and studied in combination with other bowel management methods (Nelson & Orr, 2021; Wincentak et al. 2021). Haas et al. (2005) reported that people who used a combination of DRS with manual removal of feces were 70% less likely to have an unplanned bowel evacuation (p<0.05).
Only one single pre-post study was found to investigate DRS as the primary intervention, where the results showed increased peristaltic waves in the left colon, thus increasing motility in this segment and aiding evacuation of stool for those with reflex bowel dysfunction (Korsten et al. 2007; N=6). Another study found that anal balloon inflation to dilate the rectum significantly increased rectal pressure at 6, 8, and 10 mL of inflation (p<0.001), demonstrating how DRS may induce rectal contractions for defecation through the anorectal excitatory reflex (Shafik et al. 2000). Stimulation of anorectal reflexes in people with SCI above the conus can therefore be incorporated into bowel routines; pharmacological rectal stimulants can be used to trigger evacuation at a chosen time in combination with digital rectal stimulation.
The risk of AD with DRS was evident in an RCT (Faaborg et al. 2014), who found that people with an injury above T6 demonstrated a larger systolic blood pressure increase after DRS compared to transanal irrigation methods (the authors used inconsistent terminology such as “digital anorectal stimulation” and “digital anorectal evacuation”). Although, cross-sectional data shows DRS is one of the most used interventions for bowel management (Inskip et al. 2018; N=287, Tate et al. 2023; N=18).
Conclusion
There is level 1 evidence (Faaborg et al. 2014) that people with a SCI above T6 demonstrated a larger systolic blood pressure increase after digital rectal stimulation compared to those using transanal irrigation.
There is level 2 evidence (Shafik et al. 2000) that anal dilation may be used to evoke the anorectal excitatory reflex.
There is level 4 evidence (from one pre-post study; Korsten et al. 2007) that digital rectal stimulation increases motility in the left colon.
