Abstract
Background
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Pathophysiology
• Upper motor neuron (UMN) lesions occur above the conus medullaris and are associated with hyper-reflexic bowel or an increase in tone of the intestinal wall and anal sphincter. 2 Because peristalsis remains intact, the combination of propelling stool against a tight sphincter often presents as constipation with fecal retention and impaction. Evacuation depends on initiating the rectal–colon reflex by stimulating the bowel wall digitally or with a suppository.
• Lower motor neuron (LMN) lesions are at or below the level of the conus medullaris and are associated with an areflexic bowel, characterized by a flaccid anal sphincter and slow peristalsis. 2 LMN lesions present as constipation with bowel incontinence. The major therapeutic distinction is to use stool bulking agents like fiber to prevent bowel accidents in LMN lesions.
Impact of Neurogenic Bowel
Neurogenic bowel rates are a significant cause of anxiety and distress, especially for those who require more than 15 minutes to complete bowel routines.3,4 In the critically ill, neurogenic bowel can even be life threatening and associated with viscous perforation, delirium, or difficulty weaning from a ventilator.5–7 Patients with nontraumatic spinal cord injury (SCI) have shorter life expectancies, whereas traumatic SCI patients, if getting excellent care and are not ventilator dependent, have near normal life expectancies. 8
Clinical Evaluation
Although the presence of neurogenic bowel is usually evident in traumatic SCI, clinicians may overlook it in nontraumatic etiologies such as multiple sclerosis, stroke, or cancer (see FFs #237 and 238). In patients with an insult to the spinal cord, a digital rectal examination should be performed to distinguish between UMN and LMN lesions. UMN lesions will result in a tight sphincter, whereas LMN lesions will result in a flaccid anal sphincter with no volitional contraction.
Management of Neurogenic Bowel
Despite data showing that patients with well-managed neurogenic bowel have a better quality of life, there is a paucity of controlled trials examining the best treatments.1,4,6 As a result, the following empiric recommendations arise from a consortium of SCI experts
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• Nonpharmacological measures: Routine is critical. At the same time every day, ideally about 30 minutes after a meal to utilize the gastrocolic reflex, the patient should sit on a commode while a clinician applies pressures to the abdomen in a clockwise manner for 5 minutes at a time. For terminally ill patients who cannot tolerate regular meals nor a commode, do the same with the patient on his or her side in the bed. Follow this with digital stimulation to the rectal wall in a circular motion for 20–30 seconds and, if necessary, manual disimpaction. • Pharmacological measures: Administer a 10 mg bisacodyl suppository at the same time daily. Make sure the suppository contacts the bowel wall, not just the stool itself. Once the patient is having regular bowel movements, at least every other day, transition to a glycerin suppository or a minienema (a commercially available 5 mL enema of docusate, polyethylene glycol, and glycerin). To time bowel movements for the morning, give two to four tablets of senna at bedtime. • Next steps: if these measures are ineffective after two to three days, imaging with a kidney, ureter, and bladder X-ray (KUB) may be needed to evaluate for ileus or bowel obstruction. Otherwise consider lactulose 30 mL, magnesium citrate 300 mL, or sorbitol 70% solution up to 150 mL PO, or an enema.
Special Considerations
• SCI patients are susceptible to autonomic dysreflexia (AD), an abnormal sympathetic nervous system response to a noxious stimulus below the level of the spinal cord lesion. Typical AD symptoms are diaphoresis and a rapid rise in blood pressure that can be life threatening. The definitive treatment is to remove the noxious stimulus (e.g., malfunctioning Foley, compression stockings, or impacted stool).
• Patients already on opioids will likely require higher doses as well as more frequent use of cathartics. See Fast Facts #294 and 295.
• Transanal irrigation, a self-administered irrigation consisting of a soft inflatable balloon to hold a rectal catheter in place, has been shown to be effective for refractory cases in small studies. 4
• Although more invasive, colostomy placement and electrical stimulation to the bowel have been described in select patients with longer prognoses and refractory symptoms.