Defecation following spinal cord injury

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Types of bowel dysfunction

There are two distinct patterns of bowel dysfunction after spinal cord injury (SCI), depending on whether the sacral reflexes have been affected.

Table 1: Patterns of clinical presentation of bowel dysfunction following SCI
Supraconal
(upper motor neuron [UMn] or reflex) lesion		 Conal or cauda equina
(lower motor neuron [LMn] or flaccid) lesion
Injury or damage usually at or above T12 vertebral level1 Injury or damage usually L1 vertebral level and below1
  • Positive anal and bulbo-anal reflex1
  • Inability to effectively increase intra-abdominal pressure2
  • Rectal hyperreactivity3
  • Loss of rectal sensation2
  • Loss of voluntary sphincter control3
  • Hypertonic external anal sphincter2
  • Anorectal dyssynergy2
  • Faecal impaction in the proximal colon4
  • Absent anal and bulbo-anal reflex1
  • No reflex response to increased intra-abdominal pressure2
  • Decreased rectal tone3
  • Reduced anorectal sensation3
  • Loss of voluntary sphincter control3
  • Absent external anal sphincter tone2
  • Rectal faecal impaction4

Testing bulbo-anal and sacral reflexes

Identify if the bulbocavernosus (bulbo-anal) reflex is present by:

  • applying pressure to the glans penis or clitoris, to see if a palpable and visible contraction of the anal sphincter occurs1
  • applying a gentle tug to the urethral catheter to see if a palpable anal response occurs.

Identify if there is sparing of the sacral reflexes by applying a pinprick to the person’s buttock, just lateral to the anus. If there is a visible contraction of the anal sphincter, this shows that the sacral reflexes have been spared.1

Common issues with defecation

  • Constipation
  • Difficulty with evacuation
  • Faecal incontinence

What causes issues with defecation?

Depending on the level and completeness of injury, SCI can have a number of impacts on defecation, including the following:

Time taken for movement of ingested food and liquids

  • Gastric emptying time
  • Colonic and whole gut transit time5

Changes in function

  • Altered anal sphincter tone
  • Altered pelvic floor functioning
  • Decreased ability to attain optimum position for defecation due to poor trunk control and balance or equipment available
  • Decreased ability to increase intra-abdominal pressure during defecation
  • Decreased sitting balance
  • Decreased upper limb function
  • Decreased ability to transfer

Absence or alteration of reflexes and sensation

  • The gastrolic reflex may be absent or reduced
  • The ability for a person to sense their rectum is full may be absent or altered
  • Anorectal dyssynergy1 (occurs when the muscles and nerves in the pelvic floor, including the anal sphincter fail to coordinate and relax to  allow bowel evacuation6)

  1. Coggrave M, Ash D, Adcock C, et al. Guidelines for management of neurogenic bowel dysfunction in individuals with central neurological conditions. Multidisciplinary Association of Spinal Cord Injured Professionals. 2012.
  2. Lynch AC, Antony A, Dobbs BR, Frizelle FA. Bowel dysfunction following spinal cord injury. Spinal Cord. 2001;39(4):193-203.
  3. Krogh K, Christensen P. Neurogenic colorectal and pelvic floor dysfunction. Best Pract Res Cl Ga. 2009;23(4):531-43. DOI: 10.1016/j.bpg.2009.04.012
  4. Singal AK, Rosman AS, Bauman WA, et al. Recent concepts in the management of bowel problems after spinal cord injury. Adv Med Sci. 2006;51:15-22.
  5. Williams RE, Bauman WA, Spungen AM, et al. SmartPill technology provides safe and effective assessment of gastrointestinal function in persons with spinal cord injury. Spinal Cord. 2012;50(1):81-4. DOI: 10.1038/sc.2011.92
  6. Cleveland Clinic. Anismus. Cleveland, Ohio: Cleveland Clinic; 24 May 2022 [cited 8 Nov 2022].

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