Assessment of Neurogenic Bowel

The clinical practice guidelines (CPG) for Management of Neurogenic Bowel Dysfunction (Consortium for Spinal Cord Injury Medicine, 2020) recommend several evaluations for the assessment of neurogenic bowel. After defining the level and completeness of SCI according to the ISNCSCI scale, a comprehensive evaluation of bowel function, impairment, possible complications, GI history, and physical examination of the abdomen/rectum should be completed at the onset of injury, annually as care continues, or if significant GI changes occur, to gain a sufficient understanding of one’s bowel function to inform management. The CPG (Consortium for Spinal Cord Injury Medicine, 2020) also describes more involved diagnostical tools should standard examination not be sufficient. These include abdominal x-ray, computer tomography (CT), colonic transit time testing, wireless motility capsule, anorectal manometry, anorectal physiological testing via balloon expulsion, and defecography as diagnostic tools that may help identify symptoms, prevent the progression of complications, and plan for proper intervention.

Discussion

A comprehensive assessment of NBD after SCI is used to understand an individual’s bowel function, prevent the progression of complications, and plan for proper interventions and management techniques (CSCM, 2020). The clinical diagnosis is done through a physical examination including anal tone, sensation, voluntary contractions and reflexes, and combined with patient history is usually enough to inform treatment, however other times, more sophisticated diagnostics are wanted.

Prolonged colonic transit time related to defecation disorders can be identified using wireless motility capsules, radio-opaque markers, and scintigraphy (CSCM, 2020; Alexander et al., 2009). Scintigraphy involves the administration of radionuclide and image capture of the abdomen using a gamma camera (CSCM, 2020). With this method, Krogh et al. (2002) found differences in the degree of colorectal emptying between controls (N=16) and people with conal/cauda equina lesions who reported normal defecation (N=6) (53% of the rectosigmoid vs. 0-44%, respectively, p<0.001). Findings also showed that the cumulated transit time was significantly longer in people with SCI (median 2.7 days; range 0.2-4.2 days) than in the control group (median 0.7 days; range 0-1.4 days; p<0.05) (Krogh et al. 2002). The distribution and passage of ingested radio-opaque markers throughout the colon segments are tracked to measure colonic transit time (CSCM, 2020; Krogh et al. 2002). Another study found that people with SCI who reported constipation symptoms had more retained markers than those who did not report symptoms (mean markers 49 vs 22, respectively, p=0.007) (Emmanuel et al. 2009).

Wireless motility capsules may be a useful and inexpensive alternative to gaining information about bowel motility patterns, such as gastric emptying times, small intestine transit, and total colorectal transit (CSCM, 2020; Tate et al. 2023). By using Smart Pill capsules, Williams et al. (2012) found that between the SCI and non-SCI groups, gastric emptying time (10.6±7.2 vs 3.5±1.0h, p<0.01), colonic transit time (52.3±42.9 vs 14.2±7.6 h, p=0.01), and whole gut transit time (3.3±2.5 vs 1.0±0.7 days, p<0.01) were prolonged in the SCI group. Similarly, Fynne et al. (2012) measured bowel motility patterns with a magnetic tracking pill and observed longer orocecal transit times in people with low SCI (p<0.01) and high SCI (p<0.01) compared to non-SCI controls. Although, they reported no significant difference in gastric emptying between people with SCI and the non-SCI controls (p=0.60) (Fynne et al. 2012). Abdominal radiography can also aid in identifying the presence and degree of stool in the colon and the colonic segments. Four scoring methods exist to assess severity of fecal loading on abdominal radiographs in constipated patients (Barr-, Starreveld-, Blethyn- and Leech scores). Park et al. (2013) analyzed fecal loading from radiographs in people with SCI and found there was a positive correlation between these scores and total colon transit time (Starreveld score (p<0.05) and Leech score (p<0.01)).

Physiological procedures such as anorectal manometry, determining resting and squeeze pressure, and anorectal sensibility testing can provide good diagnostic information (Alexander et al., 2009). Trivedi et al. (2016) found that people with SCI had higher rectal and sigmoid compliance than controls (p<0.05 and p=0.002, respectively) which may contribute to constipation symptoms. With a balloon expulsion test, anal manometry can help detect defecation disorders related to pelvic floor dysfunction in incomplete SCI and quantitative measures of rectal volume sensations/anorectal pressure during rest and squeeze (Tate et al. 2023). Although, use of anorectal manometry may be limited by the extensive equipment required (Alexander et al. 2009).

Other tools studied in SCI include defecography and ultrasound, primarily used when anorectal manometry/balloon expulsion tests are inconclusive, or when anatomic causes of obstruction are suspected (CSCM, 2020; Tate et al. 2023). The American Gastroenterological Association (AGA) and American College of Gastroenterology (ACG) recommend the use of defecography, a radiological imaging procedure that instills barium into the anorectum under fluoroscopy, when anorectal manometry and balloon expulsion tests are inconclusive (CSCM, 2020). Two studies (Putz et al. 2020; N=20; Putz et al. 2017; N=20) demonstrate the safety and feasibility of 3T-MR defecography as a diagnostic tool in NBD constipation examinations for people with complete paraplegia; with this method, they found that anorectal parameters significantly differ between SCI and non-SCI groups. Lastly, Kim et al. (2016b) examined the use of ultrasound to measure rectal diameter and area in people with SCI and NBD. Findings showed that after defecation, these parameters were smaller in people with UMN bowel compared to those with LMN bowel.

Conclusion

A clinical physical examination and a detailed patient history are key to diagnosing type of NBD in people with SCI.

There is level 2 evidence (Emmanuel et al. 2009) that laser Doppler flowmetry can identify altered autonomic innervation, which was evident in people with injury above the level of sympathetic outflow to the gut (T5).

There is level 2 evidence (Park et al. 2013) that plain abdominal radiography can be used as a simple and convenient method to evaluate bowel dysfunction in people with SCI.

There is level 2 evidence (Kim et al. 2016b) that rectal ultrasound can be used to determine differences in rectal diameter and area for people with UMN and LMN bowels.

There is level 2 evidence (Putz et al. 2020) that MR-defecography can detect objective parameters related to bowel incontinence and pelvic floor dyssynergia in NBD.

There is level 2 evidence (Putz et al. 2017) that 3T MR-defecography is a safe diagnostic tool for the visualization of pelvic floor parameters in people with complete paraplegia.

There is level 2 evidence (Williams et al. 2012) that SmartPill technology can detect prolonged gastric emptying, colonic transit time, and whole gut transit time in people with SCI (compared to people without SCI), demonstrating a safe, non-invasive method for GI investigation.

There is level 2 evidence (Fynne et al. 2012) that orally ingested magnetic pill tracked by the Motility Tracking System (MTS-1) can identify prolonged colonic transit times and provide information about gastric emptying and small intestinal contractions.

There is level 2 evidence (Krogh et al. 2002) that colorectal scintigraphy can help identify differences in the degree of colorectal emptying between SCI and non-SCI individuals.