What investigations should be done for chronic fecal incontinence?

Investigations for Chronic Fecal Incontinence

For chronic fecal incontinence, anorectal manometry and endoanal ultrasound should only be performed after conservative measures have been exhausted and when surgical intervention is being contemplated, as these tests primarily guide surgical planning rather than change initial management. 1

Initial Clinical Assessment

The first priority is distinguishing true fecal incontinence from diarrhea, as patients commonly misinterpret diarrhea as incontinence. 1 Key clinical features to document include:

• Type of incontinence: urge (awareness with inability to delay), passive (no awareness), or combined 2
• Severity markers: frequency, volume, consistency (solid vs liquid vs gas only), and impact on quality of life 2
• Nocturnal symptoms: waking to defecate excludes functional disorders 1
• Associated diarrhea: stool consistency using Bristol Stool Chart (type 5-7 indicates diarrhea) 1

Exclude Treatable Underlying Causes of Diarrhea

Since loose stool is the most common exacerbating factor for incontinence, investigate potential causes systematically: 1, 2

• Bile acid diarrhea: SeHCAT scan, serum 7α-hydroxy-4-cholesten-3-one, or fecal bile acid measurement 1
• Coeliac disease: anti-tissue transglutaminase antibodies 1
• Microscopic colitis: colonoscopy with biopsies from right and left colon 1
• Small bowel bacterial overgrowth: empirical antibiotic trial (testing has insufficient evidence) 1
• Pancreatic exocrine insufficiency: if steatorrhea present 1
• Inflammatory bowel disease: fecal calprotectin, colonoscopy if indicated 1

Digital Rectal Examination

A focused anorectal examination is essential and may reveal: 1

• Fecal impaction with overflow: common in elderly, cognitively impaired, or neurologically impaired patients 1
• Rectal prolapse: visible structural abnormality 1
• Sphincter tone assessment: gross defects may be palpable 3

When to Perform Specialized Anorectal Testing

Anorectal manometry and endoanal ultrasound should be reserved for specific scenarios: 1

Indications for Testing:

• Conservative measures (dietary modification, antidiarrheals, biofeedback) have failed 1, 2
• Surgical intervention is being considered 1
• Severe symptoms with major quality of life impairment 1
• History of obstetric trauma, pelvic surgery, or pelvic radiation where sphincter repair might be appropriate 2, 3

What These Tests Provide:

Anorectal manometry measures: 3, 4, 5

• Resting anal sphincter pressure (internal sphincter function)
• Squeeze pressure (external sphincter function)
• Rectal sensation thresholds
• Rectoanal inhibitory reflex

Endoanal ultrasound identifies: 3, 4, 5

• External anal sphincter defects or thinning
• Internal anal sphincter defects or thinning
• Anatomic disruption from trauma

These tests are complementary—manometry provides functional data while ultrasound provides anatomic detail. 4 However, only 2 of 27 patients in one study had completely normal findings on both tests, yet this rarely changes initial conservative management. 4

Advanced Imaging: Defecography

Defecography (fluoroscopic or MR) should be considered when: 1, 6

• Multicompartment pelvic floor dysfunction is suspected 1
• Recurrent symptoms after previous pelvic surgery 1
• Clinical examination findings are discordant with symptoms 1
• Structural abnormalities like rectocele, enterocele, or rectal prolapse need confirmation 1, 6

Defecography detects clinically occult findings in approximately one-third of patients with posterior vaginal wall bulging, including enteroceles and sigmoidoceles. 6 However, the British Society of Gastroenterology notes that evidence these tests change clinical practice is lacking outside specialist settings. 1

Common Pitfalls to Avoid

• Don't attribute symptoms to IBS if incontinence wasn't present before any pelvic surgery—systematic investigation is required 1
• Don't order specialized anorectal testing as first-line investigations—they should follow failed conservative therapy 1
• Don't miss fecal impaction with overflow—this mimics incontinence but requires opposite treatment (disimpaction, not antidiarrheals) 1
• Don't forget medication review—opioids cause constipation with overflow; other drugs may cause diarrhea 1

Conservative Management Should Precede Testing

Before any specialized testing, implement: 2, 3

• Stool consistency optimization: fiber supplements for formed stool, loperamide for diarrhea (which also increases anal sphincter tone) 2, 7
• Dietary modifications: reduce caffeine, alcohol, artificial sweeteners 1
• Biofeedback therapy: effective in the majority of patients and should be attempted before surgery 3