Neurogenic bowel dysfunction

Neurogenic bowel dysfunction (NBD) is impaired colonic and anorectal function due to disruption of the neural pathways that regulate bowel motility, sphincter control, and sensation. It results from trauma or disease affecting the central or peripheral nervous system and most commonly affects individuals with spinal cord injury (SCI), multiple sclerosis, and Parkinson disease. NBD is classified by the location of the neurological lesion: Reflexic (upper motor neuron) NBD is characterized by intact spinal reflexes and increased sphincter tone, and areflexic (lower motor neuron) NBD is characterized by lost reflexes and reduced sphincter tone. Clinical features differ based on the location of the lesion and primarily include constipation and/or fecal incontinence, but they may also include abdominal pain, bloating, and prolonged defecation time. Diagnosis is based on clinical evaluation, supported by tools such as bowel diaries, imaging, and physiological testing. Management follows a stepwise approach, starting with conservative management involving diet and fluid optimization, scheduled bowel routines, and pharmacological treatment (e.g., laxatives, suppositories). For refractory cases, more invasive options such as transanal irrigation or surgery (e.g., colostomy) may be considered.

The prevalence of NBD is up to 80% in patients with spinal cord injury or disease. ^[1]

Epidemiological data refers to the US, unless otherwise specified.

• Central nervous system lesions ^[2][3]
  • Spinal cord injury (most common); see "Etiology of spinal cord injuries."
  • Parkinson disease
  • Multiple sclerosis
  • Traumatic brain injury
  • Transverse myelitis
  • Developmental malformations (e.g., spina bifida, meningomyelocele)
  • Conus medullaris syndrome
  • Cerebrovascular disease
  • Amyotrophic lateral sclerosis
• Peripheral nervous system lesions ^[4]
  • Autonomic neuropathy (from, e.g., diabetes mellitus, amyloidosis)
  • Cauda equina syndrome
  • Postsurgical or traumatic pudendal nerve injury^[4]

• Reflexive neurogenic bowel dysfunction: upper motor neuron damage ^[5]
  • Constipation
  • Increased tone of the pelvic floor and external anal sphincter
  • Intact bulbocavernosus and anal reflexes
• Areflexive neurogenic bowel dysfunction: lower motor neuron lesion ^[5]
  • Fecal incontinence
  • Decreased or absent tone of the pelvic floor and external anal sphincter
  • Loss of reflexes (e.g., centrally mediated peristalsis and defecation reflexes, bulbocavernosus reflex, anocutaneous reflex)

Clinical features are determined by the location of the lesion and include the following: ^[1][5]

• Constipation
• Fecal incontinence (including overflow diarrhea)
• Abnormal defecation (e.g., incomplete voiding, prolonged defecation time)
• Abdominal bloating and/or pain
• Anorectal findings
  • Loss of perianal and/or deep anal sensitivity
  • Abnormal sphincter tone and/or voluntary contraction
  • Loss of anal reflex and/or bulbocavernosus reflex

• Diagnosis is based on clinical features.
• A bowel diary can help quantify symptoms. ^[6]
• Further studies are based on clinical suspicion and may include: ^[1][3]
  • Abdominal imaging (e.g., CT abdomen, x-ray abdomen): to assess for, e.g., fecal impaction, bowel obstruction, megacolon
  • Colonic transit time
  • Anorectal manometry: to evaluate pelvic floor dysfunction
• Refer to a physical medicine and rehabilitation specialist for specialized testing.

Use a standardized questionnaire (e.g., NBD score) to evaluate and monitor NBD. ^[1][5]

Management follows a stepwise approach, guided by the clinical features and patient preference.

Conservative management ^[1]

• Fluids and nutrition ^[5]
  • Avoid dehydration.
  • Gradually increase fiber intake (e.g., in diet and/or from supplements).
• Bowel care ^[3]
  • Ensure regular bowel voiding.
  • Timing: Perform bowel care 30 minutes after food or fluid intake.
  • Consider bowel evacuation techniques (e.g., digital rectal stimulation, digital evacuation).
• Pharmacological treatment ^[1]
  • Oral laxatives: for bowel movement regulation
    • Osmotic (e.g., docusate sodium)
    • Bulking (e.g., psyllium)
    • Stimulant (e.g., bisacodyl)
  • Rectal laxatives (e.g., bisacodyl suppository)

Interventional management

The following may be considered under specialist guidance for patients who do not respond to conservative management. ^[3]

• Transanal irrigation
• Surgical interventions
  • Colostomy (most common)
  • Malone antegrade continence enema ^[3]

• Perianal skin breakdown or injury
• Hemorrhoids
• Anal fissure
• Megacolon and/or megarectum ^[3]

We list the most important complications. The selection is not exhaustive.