What is the initial evaluation and management for constipation, including the use of sitz (seat) testing and anorectal manometry?

Initial Evaluation and Management of Constipation

A careful digital rectal examination (DRE) with assessment of pelvic floor motion during simulated evacuation should be performed before considering specialized testing like anorectal manometry, though a normal DRE does not exclude defecatory disorders. 1

Clinical History - Key Elements to Elicit

The history must identify the most distressing feature for the patient 1:

• Stool frequency and consistency - Document exact number of bowel movements per week and Bristol stool type 1
• Straining characteristics - Prolonged, excessive straining suggests defecatory disorders, especially if soft stools or enemas are difficult to pass 1
• Need for manual assistance - Perineal/vaginal pressure or digital evacuation strongly indicates pelvic floor dysfunction 1
• Sensation of incomplete evacuation - A hallmark of defecatory disorders 1
• Current laxative regimen - Document all medications, dosages, and frequency of use 1
• Medication review - Identify constipating agents (opiates, anticholinergics, calcium channel blockers) 1

Physical Examination - Specific Maneuvers Required

The DRE must include these specific assessments, not just a cursory examination 1:

• Perineal descent observation - With patient in left lateral position, observe descent during simulated defecation and elevation during squeeze 1
• Anal verge inspection - Look for patulous opening (suggests neurogenic constipation) or mucosal prolapse during bearing down 1
• Resting and squeeze tone - Assess internal sphincter tone and puborectalis contraction 1
• Puborectalis palpation - Acute tenderness suggests levator ani syndrome 1
• Simulated expulsion - Instruct patient to "expel my finger" to assess coordination of expulsionary forces 1
• Rectocele evaluation - Examine for presence or consider gynecologic consultation 1

Critical caveat: A normal DRE does not exclude pelvic floor dysfunction, so further testing may still be warranted if symptoms persist. 1

Initial Laboratory Testing

Only a complete blood count is necessary in the absence of other symptoms and signs. 1, 2

• Metabolic tests are NOT routinely recommended - Thyroid-stimulating hormone, glucose, calcium, and creatinine have low diagnostic utility and cost-effectiveness unless clinical features specifically warrant them 1, 2

Structural Evaluation - When to Perform

Colonoscopy or other structural imaging should be performed only in these specific circumstances 1, 2:

• Alarm symptoms present - Blood in stools, anemia, weight loss 1, 2
• Abrupt onset of constipation - Sudden change in bowel pattern 1, 2
• Age >50 years without prior colorectal cancer screening 1, 2

Options include colonoscopy (preferred), CT colonography, or flexible sigmoidoscopy with barium enema 1, 2

Initial Therapeutic Trial Before Specialized Testing

After discontinuing constipating medications when possible, a therapeutic trial should be implemented before ordering anorectal manometry or other specialized tests. 1

Step 1: Fiber and Basic Laxatives

• Gradual fiber increase - Both dietary and supplements 1
• Inexpensive osmotic agents - Milk of magnesia or polyethylene glycol 1
• Stimulant laxatives if needed - Bisacodyl or glycerol suppositories, preferably 30 minutes after a meal 1

Step 2: Assess Response

If symptoms do not respond to this initial trial, proceed to specialized testing 1

Specialized Testing - When and What to Order

Anorectal Testing Indications

Anorectal tests (manometry, balloon expulsion) should be performed in patients who do not respond to the initial therapeutic trial. 1

• Anorectal manometry - First-line test to identify anal weakness, rectal sensation abnormalities, and impaired balloon expulsion 1, 3
• Imaging (endoanal ultrasound or MRI) - Consider if surgery or device therapy is contemplated; ultrasound better for internal sphincter, MRI superior for external sphincter and pelvic floor 1

Colonic Transit Studies

Colonic transit should be evaluated if anorectal test results do not show a defecatory disorder OR if symptoms persist despite treatment of a defecatory disorder. 1, 2

Management Based on Diagnosis

For Defecatory Disorders

Biofeedback therapy rather than laxatives is recommended for defecatory disorders, with success rates exceeding 70%. 1, 4

For Normal or Slow Transit Constipation

• Long-term laxative use is safe 1
• Newer agents - Lubiprostone, linaclotide, or prucalopride (not available in US) for refractory cases 1, 5

Common Pitfalls to Avoid

• Performing anorectal manometry before an adequate therapeutic trial - This wastes resources and delays appropriate treatment 1
• Ordering metabolic panels routinely - These have low yield without specific clinical indications 1, 2
• Failing to perform a thorough DRE with simulated defecation - A cursory examination misses defecatory disorders 1
• Assuming normal DRE excludes pelvic floor dysfunction - Further testing may still be needed 1
• Performing colonoscopy without alarm features in age-appropriate screened patients - This is not indicated 1