Digital rectal stimulation as an intervention in persons with spinal cord injury and upper motor neuron neurogenic bowel. An evidenced-based systematic review of the literature

Abstract

Context: Need for evidential support of practice guideline recommendations for management of neurogenic bowel management in adults with spinal cord injury.

Objective: To determine evidence for digital rectal stimulation (DRS) as an intervention in the management of upper motor neuron neurogenic bowels (UMN-NB) in persons with spinal cord injury (SCI).

Methods: A systematic review of the literature including research articles and practice guidelines evaluating upper motor neuron neurogenic bowel treatments and the use of digital rectal stimulation was performed using OvidMedline, PubMed and the Cochrane database and included research articles and practice guidelines. Limitations were made related to English language, patient age and focus on spinal cord injured patients. Strength of evidence was assessed using the Johns Hopkins Nursing evidence-based practice model.

Results: Eleven articles were included in the systematic review. Only one used DRS as a primary intervention. There was moderate evidence for DRS in persons with SCI and UMN-NB. There was evidence of the physiologic effect of DRS and support for combining DRS with other treatment regimens.

Conclusion: There is insufficient evidence to promote any one intervention for the management of UMN-NB. The promotion of DRS, and education as to the proper technique for DRS should remain an emphasis of education of home management of UMN-NB in persons with SCI. Future research should focus on the use of standardized, validated tools to evaluate management techniques for UMN-NB.

Context

The approach to management of neurogenic bowel has relied primarily upon expert opinion and trial and error. Clinical practice guidelines put forth by the Consortium for Spinal Cord Medicine¹ primarily recommend conservative bowel management techniques such as dietary management and medications along with physical interventions including rectal stimulants and rectal stimulation to promote bowel evacuation. Given that the average age at the time of an SCI is 42 years,² the adoption of bowel evacuation techniques that are cost-effective and based on scientific evidence is important to promote health outcomes and support positive quality of life (QOL) in this population.

Digital rectal stimulation (DRS) involves the insertion of well-lubricated fingers into the rectum with stimulation applied in a circular manner with finger tips pointing towards the spine (and away from the bladder) to provide physical stimulation to the rectal wall.^3,4 DRS is an inexpensive intervention, requiring limited supplies, and is often one of the mainstays of daily bowel routines as it stimulates peristalsis and bowel evacuation.

Persons with SCI often have limitations in their fine motor skills and ability to position, dependent upon level of injury. This issue, in addition to the potential for damage to the rectal mucosa, brings into question the feasibility of DRS as a reasonable and safe long term bowel management tool for the SCI population. The goal of a long term bowel program is the promotion of bowel evacuation at a set time and schedule with the use of available resources for the maintenance of health, while promoting QOL. From the time of entrance on to the rehabilitation unit, the goal of treatments includes instructing patients on daily routines that can be reasonably and effectively continued at home to promote optimal health and independence. It is with consideration of this goal that interventions for neurogenic bowel management were systematically reviewed to determine evidence for digital rectal stimulation as an intervention in patients with spinal cord injury and upper motor neuron neurogenic bowel. Outcome measures of colonic transit time (CTT) and QOL were deemed important to support the promotion of bowel evacuation at a set time and schedule in this review.

Methodology

The literature was reviewed using Ovid Medline, PubMed and the Cochrane database to identify research articles and practice guidelines evaluating upper motor neuron neurogenic bowel (UMN-NB) treatments and the use of DRS. Key words identified for the search strategy included: upper motor neuron, neurogenic bowel, spinal cord injury, spinal cord, constipation, digital rectal stimulation, digital stimulation, quadriplegia, paraplegia, bowel management, bowel evacuation, colonic transit, bowel care, fecal incontinence.

The initial search (pre-screen) resulted in a very large number of articles, approximately 126,000. These were then limited (screened) to adults, age 18 and older, English language, and patients with spinal cord injury. No limitations were made with regard to date of publication as classic works were also desired. This refined the results to just over 10,000. Any studies including UMN-NB in patients with mixed etiology of injury, and articles that were secondary research of larger studies or non-research studies were excluded. This limited the results to 141. Further review to verify each study included adults with SCI and UMN-NB and an intervention further refined the set to 40 articles. These were reviewed for use of a primary intervention of DRS (Fig. 1). Of the 40 articles, only one study used DRS as a primary intervention. One additional study evaluated the effect of anal dilation on rectal contraction and correlated these results to the intervention of DRS and thus was included. Three other articles were found to include DRS as part of the intervention. Given the paucity of research specific to DRS for adults with SCI and UMN-NB, 6 articles with outcome measures of interest for this review such as CTT and QOL were included in the review. One article was considered a classic work and was included despite a small number of subjects being below the age criteria for inclusion. This resulted in 11 articles meeting the inclusion criteria for review. An ancestral search of the 40 articles found did not result in any additional research for review on the outcomes of interest. The classic guideline, “Neurogenic Bowel Management in Adults with Spinal Cord Injury”,¹ was excluded as it did not include a scientific research base for the use of DRS, instead citing expert opinion only. Also excluded was the Cochrane review “Management of faecal incontinence and constipation in adults with central neurological diseases”,⁵ as it included mixed etiology for the UMN-NB and was not specific to patients with SCI.

Figure 1.

Flow diagram for literature search.

Articles were critically examined using criteria established by the Johns Hopkins University School of Nursing, as described in Newhouse;⁶ the Johns Hopkins Nursing evidence-based practice model (JHNEBP). The JHNEBP model grades evidence based upon its merit with regard to research design, quality of rigor in conducting the research, review of supportive literature, and use of reliable and valid measures. Strength of evidence is from 1 to 5 (experimental randomized controlled trial or meta-analysis to expert opinion) with the quality of evidence rated A-C (high to low quality with major flaws) (Table 1).

Table 1. Johns Hopkins nursing evidence-based practice evidence levels and quality guide for quantitative studies.

Evidence levels	Quality ratings
Level I −  Experimental study, randomized controlled trial (RCT) −  Explanatory mixed method design that includes only a level I quantitative study −  Systematic review of RCTs, with or without meta-analysis	A High quality: Consistent, generalizable results; sufficient sample size for the study design; adequate control; definitive conclusions; consistent recommendations based on comprehensive literature review that includes thorough reference to scientific evidence.
Level II −  Quasi-experimental study −  Explanatory mixed method design that includes only a level II quantitative study −  Systematic review of a combination of RCTs and quasi-experimental studies, or quasi-experimental studies only, with or without meta-analysis	A High quality: Consistent, generalizable results; sufficient sample size for the study design; adequate control; definitive conclusions; consistent recommendations based on comprehensive literature review that includes thorough reference to scientific evidence.
Level III −  Nonexperimental study −  Systematic review of a combination of RCTs, quasi-experimental and nonexperimental studies, or nonexperimental studies only, with or without meta-analysis −  Exploratory, convergent, or multiphasic mixed methods studies −  Explanatory mixed method design that includes only a level III quantitative study −  Qualitative study Meta-synthesis	C Low quality or major flaws: Little evidence with inconsistent results; insufficient sample size for the study design; conclusions cannot be drawn.
Level IV −  Opinion of respected authorities and/or nationally recognized expert committees or consensus panels based on scientific evidence Includes: Clinical practice guidelines Consensus panels/position statements
Level V Based on experiential and nonresearch evidence
Includes:Integrative reviews Literature reviews Quality improvement, program, or financial evaluation Case reports Opinion of nationally recognized expert(s) based on experiential evidence

Reprinted by permission. © 2017 The Johns Hopkins Hospital/ Johns Hopkins University School of Nursing.

Evidence

The study designs of the eleven studies included randomized clinical trial, level I,¹ and quasi-experimental, level II.⁷ The quality of the evidence was assessed and determined to be high (grade A), good (grade B) or low with major flaws (grade C). This was determined by grading the strength of the study design with regard to sample size, randomization of subjects, intervention and control groups, consistency of treatment control, and description of data collection methods. Study results were considered with regard to their presentation and interpretation; study conclusions were assessed based on the presentation of results, limitations of the study, and the ability to apply findings to patient care (6). Of the 11 studies selected, 3 were graded high (A), 7 good (B), and 1 low (C) (Table 2).

Table 2. Level of evidence.

Study	LEVEL	QUALITY	n	Primary intervention
Amir et al.	II	C	7	Enema, suppository, DRS, abd massage
Shafik et al.	II	B	18	DRS
Tsai et al.	II	B	22	Functional magnetic stimulation
Korsten et al.	II	B	6	DRS
Binnie et al.	II	B	20	Pelvic parasympathetic stimulation
Cornell et al.	II	B	60	Irritant medications, Stimulant medications, Mechanical evacuation
Valles et al.	II	A	18	Sacral anterior root stimulation
Del Popolo et al.	II	A	33	Transanal irrigation
Ayas et al.	II	A	24	Abdominal massage
Steins et al.	II	B	14	Suppositories
Christensen et al.	I	B	87	Transanal irrigation

John's Hopkins Nursing Evidence-Based Practice level and quality: Evidence levels ranked I-II with Quality rated A-C.

The number of patients enrolled in each study ranged from 6-87. Age ranges of participants were 18–76 with the majority of studies focusing on male patients. Interventions included DRS (the focus of this review) transanal irrigation, contact irritants such as suppositories, nerve stimulation, orally ingested stimulant medications, mechanical evacuation and dietary modifications. Study outcome measures were variable, but each study included at least one of the following: Bowel function, colonic transit time, QOL related to bowels, incontinence scoring, total bowel evacuation time or frequency of rectal contractions. The exceptions to this were the two studies on DRS which focused on peristaltic contractions and rectal pressures which were then extrapolated to bowel evacuation time and bowel function. The evidence, presented by primary intervention of each study, is as follows.

Intervention: digital rectal stimulation

Two studies focused solely on DRS as an intervention, one directly, and one through the application of pressure to the rectum with extrapolation of findings to DRS. The first study, Korsten et al.⁸ included 6 males with SCI and UMN-NB, age 44–55. Manometric evaluation of peristaltic contraction via insertion of a probe into the left colon was performed. Subjects served as their own controls and were evaluated before and after DRS was applied. The mean number of peristaltic waves per minute significantly increased during and after DRS (P = 0.05). Full evacuation of the bowels was noted after three to five cycles of DRS, with the longest duration of time to complete evacuation being 13 min. Shafik et al.'s⁹ study was a controlled randomized study of the effect of dilatation of the anal canal by a balloon-tipped catheter on rectal pressure. Eighteen healthy volunteers (10 men and 8 women,) and nine patients with SCI and UMN-NB (6 men and 3 women,) were evaluated. Repeated measures were taken before and after pudendal nerve block to paralyze the external anal sphincter to isolate the effects of internal anal sphincter dilation from external. The researcher found that distention of the anal canal resulted in a significant (P < 0.001) pressure rise. This data was extrapolated to simulate DRS on rectal pressures and the evacuation of bowels.

Three studies included the use of DRS in the study protocol, but not as the primary intervention. The first study compared four approaches to bowel care: Bisacodyl suppository, glycerin suppository, mineral oil enema or Docusate sodium mini enema.¹⁰ DRS and abdominal massage supplemented each intervention. Seven subjects with SCI and UMN-NB ages 21–76 were evaluated. Colonic transit times were measured after one week of treatment with each of the 4 above noted interventions. Repeated measures design was used. Docusate sodium mini enemas resulted in the fastest total CTT with mineral oil enema, bisacodyl suppository and glycerin suppository demonstrating longer transit times. (32, 34.5, 47.6, and 48 h respectively.) Segmental CTT's were evaluated and a significant reduction in bowel evacuation time (P < 0.01) was found with Docusate sodium mini enema. Ayas et al.⁷ studied the effects of abdominal massage on bowel function in 24 inpatients with SCI UMN-NB in Turkey. All patients received a high fiber diet and DRS as a part of the study protocol. Patients served as their own controls and were evaluated for CTT and time to bowel evacuation as well as the frequency of defecation and the presence of incontinence before and after the intervention of abdominal massage. No significant increase in CTT of any single section of the colon was noted, but overall CTT was noted to significantly decrease after abdominal massage (P = 0.05). Additional findings included a reduction in fecal incontinence (P = 0.031), and increased frequency of defecation (P = 0.006). The final study including DRS was a comparison of polyethylene glycol versus vegetable oil-based bisacodyl suppositories.¹¹ 14 male patients with SCI and UMN-NB were examined. Subjects served as their own controls and underwent six consecutive bowel care procedures with both interventions. Time to flatus and time to defecation were outcomes of interest. Time to both flatus and defecation was significant (P < 0.002) for polyethylene glycol-based bisacodyl suppositories. Episodes of incontinence were also noted to be significantly less (1 versus 15) for the polyethylene glycol intervention.

Intervention: transanal irrigation

Transanal irrigation was the primary intervention for two studies. The first study was the only randomized controlled study found on UMN-NB interventions. This study by Christensen et al.¹² examined 87 patients with SCI and UMN-NB across five European countries. 25 female and 62 males were randomized to either transanal irrigation or conservative bowel management. Outcomes evaluated included multiple validated measures. Statistically significant results were found supporting transanal irrigation over conservative bowel management techniques on every outcome measured. Most significant were the outcomes on improvement in QOL (P = 0.000009), Cleveland Clinic constipation scoring system (P = 0.0016) and the bowel function score (P = 0.0048). The second study by Del Popolo et al.¹³ was of transanal irrigation for patients with SCI and UMN-NB. Thirty-three patients, 18 male and 15 female, served as their own controls and were evaluated pre and post-intervention. Use of the transanal irrigation system was correlated with a reduction in episodes of incontinence (P = 0.002), time until bowel evacuation (P = 0.004), QOL related to bowels (P = 0.001), and degree of satisfaction with bowel program (P = 0.001).

Intervention: electrical or magnetic stimulation

Three studies examined the use of electrical stimulation of nerves to promote bowel evacuation. Valles et al.¹⁴ evaluated patients prior to implant of a sacral anterior root stimulator and 12 months after. 18 patients with SCI and UMN-NB (9 male and 9 female) were studied. Of interest to note is that prior to implantation, 15 of the 18 patients used DRS as a regular means to promote bowel evacuation. CTT was examined using highly specific tools such as anorectal manometry and surface EMG. After sacral anterior root stimulator implantation, 12 of the patients continued to require DRS to promote bowel evacuation. However, the mean number of methods used to promote bowel function decreased significantly (P < 0.05). Additionally, the frequency of bowel evacuations was increased with the majority of patients experiencing daily bowel evacuation (P < 0.05). Pelvic parasympathetic stimulation was evaluated by Binnie et al.¹⁵ A three-group design was used. A control group of 10 healthy adults (8 male and 2 female) was compared with 10 patients with SCI and UMN-NB (9 males and 1 female) and a second group of 7 patients with SCI and UMN-NB who had been implanted with a sacral nerve root stimulator (6 males and 1 female). No significant difference in oro-cecal transit time was noted, but oro-anal transit time was found to be significantly different in the control group when compared to the SCI group (P < 0.01). The authors noted in subjects with paraplegia “the stool collection was by manual evacuation”¹⁵ but did not specify if DRS was performed. A non-significant decrease in transit time was noted between the stimulator and SCI groups. Frequency of defecation was significantly different between the control and the SCI group, as well as the SCI group and the stimulator group (P < 0.01). No significant difference in the frequency of defecation was noted between the control and the stimulator group. The final study examined the effect of functional magnetic stimulation on spinal nerves. Twenty-two SCI patients in Taiwan with UMN-NB (19 male and 3 female) were evaluated in a study by Tsai et al.¹⁶ Patient served as their own controls and CTT was noted to be significantly decreased after intervention (P < 0.001). Symptoms of constipation significantly decreased (P < 0.02) as assessed by a validated bowel symptom questionnaire.

Intervention: other

The final study reviewed was a classic work from 1973. Cornell et al.¹⁷ examined 3 different bowel programs in 60 patients with SCI and UMN-NB (52 males and 8 females). Patients were randomized to either oral and rectal irritant medications, stimulant medications or mechanical evacuation without orals. Statistically significant results were noted only for the outcome of time to evacuation (P values not provided) for manual evacuation versus the other two protocols. The use of mechanical evacuation was also statistically significant in increasing the frequency of evacuations as well as reduction of incontinence episodes.

Outcomes

Daily bowel evacuation: No studies directly evaluated daily bowel evacuation. Valles et al.¹⁴ evaluated frequency of bowel movements as a primary outcome. They noted that frequency of bowel movements was significantly increased after implantation of a sacral anterior root stimulator (P < 0.05). Korsten et al.⁸ evaluated the complete evacuation of the bowel after DRS and noted that evacuation occurred after the third to fifth cycle of DRS in all subjects. Valles et al.'s¹⁴ study was flawed in regards to control of the study. All patients evaluated required additional methods of bowel evacuation in addition to the sacral anterior root stimulator. This, in addition to a lack of tools validated to this particular intervention, and a limited review of the literature limited the strength of their study. Korsten et al.⁸ also had limited strength based upon a small sample size, limited review of the literature, and a lack of control of confounding variables. Their study would have been strengthened if they had reviewed the physiology of the bowel and how stimulation of the rectum may contribute to bowel evacuation as well as by controlling the environment with regard to dietary intake, concurrent medications and mechanical methods for bowel evacuation.

Colonic transit time: Eight of the 11 studies examined CTT. The use of Docusate sodium mini-enemas, abdominal massage, nerve stimulation, tap water enema with bulk softener, DRS, and polyethylene glycol-based bisacodyl suppositories were all found to improve CTT's (P values ranging from 0.0005 to 0.05). Both the application of abdominal massage⁷ and implantation of a sacral anterior root stimulator¹⁴ showed the greatest quality of evidence (A) with good strength (II). A small sample size and duration of study period in the abdominal massage study and the use of concurrent methods of bowel evacuation (lack of control) and limited literature review did not distract from the quality of evidence with regard to CTT. Stimulation of the sacral nerve roots was the most widely examined intervention with regard to CTT. Parasympathetic stimulation as described by Binnie et al.¹⁵ demonstrated a non-significant decrease in colonic transit times between normal control patients and those implanted with the stimulator suggesting a return to near normal CTT after implant. Tsai et al.¹⁶ demonstrated a significant decrease in CTT of patients serving as their own controls after functional magnetic stimulation (P < 0.001) while Valles et al.¹⁴ noted a decrease in CTT after implantation of a sacral stimulator. These studies were limited by a number of patients lost to follow up limiting the strength of the findings, as well as lack of control with patients using additional means of bowel evacuation despite stimulation. These studies would be improved by controlling for confounding factors of additional means of bowel evacuation and adherence to treatment regimen.

Quality of life: Four studies examined QOL as a primary outcome, while three additional studies looked at episodes of incontinence as a primary outcome of interest, which could be correlated with satisfaction and QOL given the goal of promotion of bowel evacuation at a set time and schedule to promote QOL. Both the studies with a quality A grade incorporated QOL as an outcome, either directly or through evaluation of incontinence. Ayas et al.⁷ looked at episodes of incontinence and found a significant decrease in episodes of incontinence after abdominal massage, suggesting an improvement in QOL rating. Valles et al.¹⁴ looked at QOL as a primary outcome. Satisfaction with the bowel program was noted to improve after implant of a sacral anterior root stimulator, which related to increased QOL. Christensen et al.'s¹² study on transanal irrigation (Level I evidence) utilized two validated tools to correlate improve QOL with transanal irrigation. The lack of control exhibited by the concurrent use of other means of bowel evacuation did not take from the strength of the evidence provided. Del Popolo et al.¹³ also examined the effect of transanal irrigation on QOL. They found intervention significantly improved QOL to a P = 0.001 level with the primary limitation to the study being lack of long-term follow up of patients after treatment.

Discussion

This literature review has established that there is insufficient evidence to promote any one intervention over another for the management of UMN-NB. The evidence leans towards transanal irrigation as an effective intervention, with the strongest level of evidence in this review (I) being in favor of transanal irrigation. However, this intervention involved specialized equipment, increased dexterity of the upper extremities, and resulted in a number of system failures secondary to rectal contraction. Additionally, the literature suggests a greater effect in less mobile patients making this intervention less applicable to the SCI population as a whole. Newer interventions, such as electrical stimulation of the nerve roots, show promising results. However, the advanced intervention of surgery to effectively manage the bowels brings to question the risk versus benefit of these procedures. Larger studies with stricter control on cofounding factors (use of concurrent means of bowel evacuation) are needed to establish the long-term effectiveness of electrical stimulation in UMN-NB care.

The management of UMN-NB's has not significantly changed since the publication of the Consortium for Spinal Cord Medicines 1998 guidelines for the management of neurogenic bowel in patients with SCI.¹ Their recommendations of the use of multiple techniques for the successful evacuation of bowels at set times of day, tailored to the individual patients needs is supported by this literature review. The inclusion of DRS as an intervention in the majority of the reviewed articles suggests that DRS should continue to be a primary intervention for the management of UMN-NB. However, further studies isolating DRS as an intervention are needed. The use of standardized, validated tools to evaluate the effectiveness of future research will improve the strength of evidence in the literature to allow future generations of providers to appropriately treat this common sequela of SCI.

With respect to the newly injured with UMN-NB, digital rectal stimulation should continue to be the primary educational tool used to promote daily bowel evacuation. Emphasis on the procedure of DRS should be made with consideration to the findings of Kortsen et al.⁸ and Shafik et al.⁹ Optimal stimulation time is one minute, with contractions continuing for 3–5 min after cessation of stimulation, allowing for ongoing peristaltic contraction after removal of the fingers without ongoing risk of damage to the rectal mucosa. The addition of transanal irrigation techniques to the bowel regime when evacuation is not achieved by DRS should be considered, given the strong levels of evidence supporting its ability to improve bowel-related QOL.

Clinical guidelines serve to standardize care practices across the continuum of care, allowing best practice to emerge to promote optimal patient outcomes. The ongoing evaluation of these guidelines must be made to assure best practice extraction from research. In the case of management of UMN-NB, the guidelines may benefit from minor additions, but patients would best benefit from ongoing research on the best practices to promote daily bowel evacuation and promote quality of life.

Conclusions

Based on the published studies included in this review, the use of DRS in patients with SCI and UMN-NB is moderately supported through two level II studies with B quality evidence. The physiologic effect of DRS was demonstrated which supported the guidelines use of digital stimulation in short duration cycles with a relaxation period between. Additionally, the literature supported the fact that DRS does induce contractions which are capable of completely evacuating the bowel. The addition of DRS to other treatment regimens was supported in the literature through studies evaluating the effect of electrical stimulation, use of oral agents, and use of rectally inserted agents ability to improve CTT's and reduce episodes of incontinence. However, the inclusion of DRS in these studies was one of the limitations of their design demonstrating a lack of control of confounding factors. As DRS is an inexpensive intervention, requiring limited supplies, it is often one of the mainstays of daily bowel routines. DRS is important with consideration of the goals of a bowel program; to promote bowel evacuation at a set time of day. However, further research is needed to establish the benefit of DRS over the potential risk of damage to the rectal mucosa. Additionally, although providers encourage daily bowel evacuation, patients may not desire increased frequency of bowel evacuation which can be time-consuming, may require the assistance of another person, and has a social stigma associated with its performance. DRS has been demonstrated to promote rectal contraction within a short duration of time. Further studies over longer durations of time with adequate sample sizes continue to be needed regarding this basic intervention for bowel management. Additionally, longitudinal studies and safety studies should be considered to reflect the chronic nature of bowel management in the spinal cord injured population taking into account the effects of daily bowel management on an aging population.

Disclaimer statements

Funding The authors of this paper certify there was no financial support associated with this manuscript.

Conflicts of interest The authors of this paper certify that they have NO conflicts of interest to report. (Including no affiliations with any organizations or financial interests in any organizations associated with the subject matter of this manuscript.)