Predictors of Bowel Dysfunction

What factors predict or affect the extent of bowel dysfunction?

Level of Injury

The vertebral level (or level of injury) to the spinal cord often determines how much function or dysfunction a person with SCI will have. Bowel dysfunction generally presents in two forms: hyperreflexic (or ‘spastic’) and areflexic (or ‘flaccid’). It is also often characterized as Upper Motor Neuron (UMN) bowel syndrome or Lower Motor Neuron (LMN) bowel syndrome.

A hyperreflexic bowel is due to an upper motor neuron injury usually above T12 (i.e., originates from a spinal cord injury above the conus medullaris which contains the sacral reflex centre). It is distinguished by the increased tone of the colon and anus. The anal sphincter remains contracted, which leads to difficulty for stool to exit out the body. If left unmanaged, constipation and severe fecal impaction can occur. Fecal incontinence (losing stool involuntarily) is still possible because rectal reflexes are still functional. These reflexes may be triggered by the presence of stool, a suppository, or enema, which can cause stool to be propelled out involuntarily.

The second form of bowel dysfunction, areflexic bowel, is due to a lower motor neuron injury usually below T12, such as an injury at the cell bodies of the conus medullaris or distal (sacral roots or cauda equina). Unlike a hyperreflexic bowel, an areflexic bowel features a flaccid sphincter and decreased activity of the intestines (distal to transverse colon) and the loss of rectal reflexes. The outcome of this is severe increase in transit time through the large intestine. The increased transit time and slow movement through the lower colon allows for excess fluids to be absorbed from the stool, often leading to hard, difficult to evacuate stool, which in combination leads to severe constipation. On the other hand, loss of sphincter tone and voluntary control leads to incontinence.

Completeness of Injury

The completeness of an injury also plays a role in determining the extent of a bowel problem. For incomplete individuals, some sense of how full the rectal is may still be intact along with the ability to control the sphincter. Even so, bowel activity may be abnormal or weakened.

Discussion

Neurogenic Bowel Dysfunction (NBD) is common in people with SCI; estimates range from 30-95% of people with SCI having some kind of bowel dysfunction, with approximately half (40-50%) having moderate to severe degrees of NBD (Elmelund et al. 2019; Stoffel et al. 2021; Liu et al. 2009; Liu et al. 2010).

Some research shows that level of injury can predict bowel outcomes post-SCI. Liu et al. (2009; N=128; 2010; N=142) reported that the risk of having severe NBD was approximately 13 times greater in people with SCI scored AIS A compared with AIS D. Liu et al. (2010; N=232) similarly found that those with a cervical injury (odds ratio (OR 10.5, 95% CI 1.6–67.7) or a thoracic injury (OR 7.1, 95% CI 1.2–40.3) had a higher risk of severe NBD than those with a lumbar injury. Lynch et al (2000 N=467 SCI, 668 control) also reported that the higher the level of injury, the more often people with SCI will require assistance or care (p≤0.0002).

People with complete SCI are also approximately 2x more likely to have severe NBD than those with incomplete SCI (p=0.01) (aOR=2.1, CI: 1.7–2.6 – Squair et al. 2019; N=47,868; OR=1.98, p=0.046 – Adriaansen et al. 2015; N=258). Tate et al. (2016; N=291) found paraplegia (complete and incomplete) and incomplete tetraplegia to be significantly (all p⩽0.05) associated with reduced bowel dysfunction. Lynch et al. (2000; N=467 SCI, 668 control) also found that incontinence was more likely to affect the life of a person with SCI if they had a complete injury.

Other research shows additional factors that can predict bowel dysfunction in people with SCI. Pavese et al. (2019; N=684) and Khan et al. (2021; N=277) found that the ISNCSCI exam total motor score could predict independent bowel function 1-year following SCI with more than 80% accuracy (Pavese et al. 2019; N=167; Khan et al. 2021; N=277; aROC 0.864-0.869). Elmelund et al. (2019; N=684) found three key components that were associated with fecal incontinence in SCI: wheelchair use compared with walking without aids (p<0.0001 and p=0.04), completeness of the paraplegic injury (p<0.0001 and p=0.04), and increased age (p=0.03).

Understandably, NBD and the need to manage bowel issues may cause significant stress and anxiety and has a negative impact on people with SCI, and on their quality of life (QoL) (Braaf et al. 2017). Social interaction outside someone’s own home is often limited by limited or inaccessible bathroom facilities (Braaf et al. 2017). Inskip et al. (2018) found that NBD had a more significant impact on QOL than sexual dysfunction (p=0.024), bladder dysfunction (p<.0001), pain (p=0.013), spasticity (p<.0001), using a wheelchair (p<.0011), and skin integrity issues (p<.0001). Research also shows that people with SCI are 1.8x more likely to be unemployed, and that 54-70% of people with SCI and bowel dysfunction say it affects their social life and relationships (Inskip et al. 2018). Pazzi et al. (2021; N=354) found that people with SCI most often cite improvement in bowel/bladder function and elimination of dysreflexia (60.4%) when asked about their functional goals. Conversely, other research shows that satisfaction with bowel care programs is reported to increase QoL in people with SCI, as does having adequate social and/or carer support (Braaf et al. 2017).

Conclusion

There is level 2 evidence that (Pavese et al. 2019) ISNCSCI total motor score could predict independent, reliable bowel management at one year after SCI for 81-84% of participants.

There is level 2 evidence (Jiang et al. 2019) that people who experience adverse events within six months post traumatic SCI were more likely to have bowel function impairment.

There is level 3 evidence (Attabib et al. 2021) that a shorter time from injury to rehab admission was a significant predictor for improved bowel function.

There is level 3 evidence (Lynch et al. 2000) that incontinence was more likely to affect the life of a person with SCI if they had a complete injury. They also reported that the higher the level of injury (incomplete and complete) the more often assistance is required (p≤0.0002).

There is level 5 evidence (Squair et al. 2019) that SCI is associated with increased odds of bowel disorders and gastric ulcers, with complete SCI being associated with increased odds of bowel incontinence.

There is level 5 evidence (Elmelund et al. 2019) that daily to monthly bowel dysfunction was more commonly associated with permanent use of a wheelchair, a more complete injury, increasing age, and injury follow-up of less than three months.

There is level 5 evidence (Tate et al. 2016; Adriaansen et al. 2015) having incomplete paraplegia (p<.05), complete paraplegia (p<.01), or incomplete tetraplegia (p<.05) were all associated with less bowel dysfunction.

There is level 5 evidence (Liu et al. 2009; Liu et al. 2010) that NBD is common in people with SCI (30-95% have some kind of bowel dysfunction) and that odds for severe NBD are up to 13x greater for people with AIS A vs. AIS D, 10x greater for people with cervical injuries, and 7x greater for people with thoracic injuries vs. those with lumbar injuries.

There is level 5 evidence (Dietz et al. 2021) that bowel management is more likely to change within the first five years after SCI.

There is level 5 evidence (Pazzi et al. 2021) that bowel function improvement is among the most common functional goals for people with SCI seeking experimental therapies. These goals may be influenced by age, level, and completeness of injury.

There is level 5 evidence (Gong et al. 2021) that patients with traumatic SCI, sacral injury, or cauda equina syndrome who suffer bladder or bowel accidents (p<0.001), with more than one bladder or bowel complication (p<0.001), and those with an NBDS ≥14 (p<0.001), reported poorer QOL.

There is level 5 evidence (Stoffel et al. 2021) that almost half of people with SCI experience severe bowel symptoms, which may be associated with more severe autonomic dysreflexia, having an indwelling catheter, or reconstructive surgery.

There is level 5 evidence (Inskip et al. 2018) that bowel dysfunction had a more significant impact on QOL than effects of sex dysfunction (p=0.024), bladder dysfunction (p<.0001), pain (p=0.013), spasticity (p<.0001), using a wheelchair (p<.0011), and skin integrity issues (p<.0001).