Neurogenic Bowel Dysfunction Workup

Updated: Feb 10, 2023
  • Author: Juan L Poggio, MD, MS, FACS, FASCRS; Chief Editor: Elizabeth A Moberg-Wolff, MD  more...
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Basic Studies

Patients older than 50 years should undergo annual stool testing for occult blood. In patients with diarrhea of unknown etiology, stool examination for fecal leukocytes, Clostridioides (formerly Clostridium) difficile toxin, and ova and parasites should be performed.

An abdominal radiograph is useful for evaluating megacolon and distribution of feces.


Studies to Assess Structure and Function

Incontinence and evacuation can be investigated by tests that assess sphincter structure and function, such as anorectal manometry and endoanal ultrasonography (EAUS). Anorectal and pelvic floor function can be assessed by means of defecating proctography and nerve conduction studies. Luminal integrity and colonic function can be evaluated by means of endoscopy and transit studies. [8]

Anorectal manometry

Anal manometry is performed by placing a water-based catheter balloon system into the distal rectum and withdrawing it through the anal canal in a stepwise manner or using a solid-state device containing microtransducers to measure anal canal pressure at various points along the catheter. This study can be employed to determine the resting and voluntary squeeze pressures of the anal canal, the length of the canal, the Valsalva reflex, and the presence of the rectoanal inhibitory reflex. [13]

Endoanal ultrasonography

EAUS evaluates sphincter integrity by using an internal rotating microtransducer. Normally, the external sphincter is a hyperechoic circumferential structure, and the internal sphincter is hypoechoic. Defects and scarring appear as incomplete rings. [8]

Defecating proctography

Video fluoroscopy provides structural and functional information during defecation. An oral contrast agent is given to delineate the small bowel, and barium is placed into the rectum. X-rays are taken while the patient attempts to defecate.


Electromyography (EMG) uses needle electrodes placed into the puborectalis or external anal sphincter to assess the state of the muscle and innervating nerve as a function of electrical activity during the resting and contractile phases.

Sensory testing

Rectal sensory function is evaluated by means of rectal balloon insufflation. The balloon is progressively distended until particular sensations are perceived by the patient. The volumes at which these sensations are perceived are recorded. The following three sensory thresholds are usually defined [26] :

  • Constant sensation of fullness
  • Urge to defecate
  • Maximum tolerated volume


Endoscopic studies, such as rectosigmoidoscopy, anoscopy, and colonoscopy, can be used to visualize anatomic abnormalities or lesions; however, they cannot assess the function of the gastrointestinal (GI) tract.