What is the recommended diagnostic workup and treatment for a patient with ongoing severe constipation?

Diagnostic Workup for Ongoing Severe Constipation

Begin with a detailed digital rectal examination (DRE) that includes assessment of pelvic floor motion during simulated evacuation before ordering any imaging or specialized testing. 1

Initial Clinical Assessment

History Taking

• Document bowel pattern specifics: date of last defecation, frequency, stool consistency (using Bristol Stool Scale), recent changes in pattern, presence or absence of urge to defecate, and sensation of complete evacuation 2
• Screen for red flag symptoms: blood in stool, mucus, need for digital manipulation to evacuate, fecal incontinence, unintentional weight loss, or abrupt onset of constipation 1
• Complete medication review: specifically identify opiates, anticholinergics, calcium channel blockers, and other constipating medications that should be withdrawn if inappropriate or unnecessary 2, 1
• Assess lifestyle factors: eating and drinking habits, physical activity level, privacy for defecation, and current living situation (living alone, with family, or in nursing home) 2
• Evaluate comorbidities: pre-existing irritable bowel syndrome, diverticular disease, heart failure, chronic pulmonary disease, and psychiatric disorders 2

Physical Examination

• Abdominal examination: assess for distension, masses, liver enlargement, tenderness, and bowel sounds 2
• Perineal inspection: check for skin tags, fissures, prolapse, anal warts, and perianal ulceration 2
• Digital rectal examination must assess: resting sphincter tone, squeeze augmentation, puborectalis muscle contraction during squeeze, perineal descent during simulated evacuation, presence of impacted feces, hemorrhoids, masses, or stenosis 1
• Critical functional assessment: ask the patient to "expel my finger" during simulated defecation to evaluate for dyssynergia 1

Important caveat: A normal digital rectal examination does not rule out defecatory disorders, so do not rely solely on this finding to exclude pelvic floor dysfunction 1

Laboratory Testing

Order only a complete blood count (CBC) in the absence of other symptoms—this is the single necessary routine test. 1

• Metabolic panels should NOT be routinely ordered unless specific clinical features warrant them 1
• Check corrected calcium and thyroid function ONLY if clinically suspected based on other symptoms such as hypercalcemia signs (polyuria, polydipsia, confusion) or hypothyroidism symptoms (fatigue, cold intolerance, weight gain) 2, 1

This approach avoids excessive metabolic testing without clinical indication, which increases costs without proven benefit 1

Structural Evaluation (Imaging/Endoscopy)

Indications for Colonoscopy

Colonoscopy is indicated ONLY if:

• Alarm symptoms are present (blood in stool, anemia, weight loss) 1, 3
• Abrupt onset of constipation 1, 3
• Age over 50 years without previous colorectal cancer screening 1, 3

Colonoscopy is the first-line structural imaging option due to its direct visualization and biopsy capability 1, 3

Alternative Structural Imaging

• CT colonography: excellent alternative when colonoscopy is contraindicated 3
• Flexible sigmoidoscopy combined with barium enema: effective combination for structural evaluation 3
• Plain abdominal X-ray: although limited as a tool in itself, may be useful to image the extent of fecal loading and to exclude bowel obstruction, but should NOT be used as a primary diagnostic tool 2, 3

Critical pitfall to avoid: Do not skip structural evaluation in high-risk patients (alarm symptoms, age >50 without screening, or abrupt onset) 1

Specialized Functional Testing

These tests should ONLY be ordered after:

1. A trial of fiber supplementation and over-the-counter laxatives has failed 1
2. Initial evaluation suggests defecatory disorder or slow-transit constipation 1

Colonic Transit Studies

Indications:

• Persistent symptoms despite treatment 1
• Anorectal tests do not show defecatory disorder 1

Method: Radiopaque markers ingested with serial abdominal radiographs to assess transit time 1, 3

Anorectal Manometry

Indications:

• Digital rectal examination suggests pelvic floor dysfunction 1
• Patient reports prolonged straining, need for perineal/vaginal pressure to evacuate, or digital evacuation of stool 1

Defecography (Fluoroscopic or MR)

Indications:

• Suspected defecatory disorders when anorectal manometry is inconclusive 3
• Can diagnose rectocele, intussusception, and abnormal pelvic floor descent 4

MR defecography provides high soft-tissue contrast for direct visualization of pelvic organs and floor muscles 3

Critical pitfall: Do not proceed to specialized testing before attempting empiric fiber/laxative trial 1

Patient-Reported Outcome Measures

• Use the Bowel Function Index (BFI) as a validated tool for assessing constipation severity, particularly for opioid-induced constipation 1
• Consider medication for BFI score ≥30 points with no response to initial laxatives 1

Algorithmic Approach Summary

1. Start with thorough history and DRE (including simulated evacuation assessment) 1
2. Order CBC only (no routine metabolic panels unless clinically indicated) 1
3. Perform colonoscopy if alarm symptoms, age >50 without screening, or abrupt onset 1, 3
4. Trial of fiber and over-the-counter laxatives (osmotic or stimulant) 2
5. If refractory, order functional tests: colonic transit studies and/or anorectal manometry based on clinical suspicion 1
6. Consider defecography if defecatory disorder suspected but not confirmed 3

Special Considerations for Severe Constipation

• More extensive investigation is warranted for those with severe symptoms, sudden changes in bowel movement number and consistency, blood in stool, and for older adults relative to their health and stage of disease 2
• If faecal impaction identified on DRE: suppositories and enemas are preferred first-line therapy 2
• Enemas are contraindicated in neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal/gynecological surgery, recent anal/rectal trauma, severe colitis, toxic megacolon, undiagnosed abdominal pain, or recent pelvic radiotherapy 2