What is the step‑by‑step approach to evaluating and treating constipation in an adult patient without red‑flag symptoms?

Step-by-Step Approach to Constipation in Adults

Begin with a digital rectal examination assessing pelvic floor motion during simulated evacuation, combined with targeted history-taking, before ordering any tests or imaging. 1

Step 1: Initial Clinical Assessment

History Components

• Document specific bowel pattern details: date of last defecation, frequency, stool consistency (using Bristol Stool Scale), and recent changes 1
• Assess for red flag symptoms requiring urgent evaluation:
  • Blood in stool or rectal bleeding 1, 2
  • Unintended weight loss 1, 2
  • Abrupt onset constipation (especially in older patients) 1, 2
  • Need for digital manipulation to evacuate 1
  • Fecal incontinence 1
  • Anemia 1
• Evaluate sensation of urge to defecate and feeling of complete evacuation 1
• Review all medications, specifically identifying opiates, anticholinergics, calcium channel blockers, and diuretics 1
• Assess lifestyle factors: fluid intake, physical activity level, dietary fiber, and privacy/comfort for defecation 1
• Screen for comorbidities: hypothyroidism, heart failure, chronic pulmonary disease, irritable bowel syndrome, diverticular disease 1

Physical Examination

• Digital rectal examination must include: 1
  • Resting sphincter tone and squeeze augmentation
  • Puborectalis muscle contraction during squeeze
  • Perineal descent during simulated evacuation
  • Patient's ability to "expel my finger" during simulated defecation 3
  • Presence of impacted feces, hemorrhoids, masses, or stenosis
• Abdominal examination: assess for distension, masses, liver enlargement, tenderness, and bowel sounds 1
• Perineal inspection: check for skin tags, fissures, prolapse, anal warts, perianal ulceration 1

Step 2: Laboratory Testing

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

• Check corrected calcium and thyroid-stimulating hormone only if clinically suspected based on other symptoms (e.g., fatigue, cold intolerance, hypercalcemia symptoms) 1, 4
• Avoid routine metabolic panels without specific clinical indication 1

Step 3: Determine Need for Structural Evaluation

Colonoscopy is indicated if any of the following are present: 1, 4

• Alarm symptoms (blood in stool, anemia, weight loss)
• Age >50 years without previous colorectal cancer screening
• Abrupt onset of constipation
• Family history of colorectal cancer 5

If colonoscopy is contraindicated, alternatives include CT colonography or flexible sigmoidoscopy with barium enema 4

Do not order plain abdominal radiographs for diagnostic purposes—they have limited utility. 4

Step 4: Initial Treatment Trial (Before Any Specialized Testing)

Non-Pharmacologic Measures (Implement First)

• Ensure privacy and comfort for defecation 6
• Position patient to assist gravity (small footstool may help exert pressure more easily) 6
• Increase fluid intake 6
• Increase activity and mobility within patient limits (even bed to chair) 6
• Educate patients to attempt defecation at least twice daily, usually 30 minutes after meals, straining no more than 5 minutes 6

Pharmacologic First-Line Treatment

Osmotic laxatives are preferred first-line agents: 1

• Polyethylene glycol (PEG) 17g/day is the preferred option, particularly for elderly patients (good safety profile) 6, 1
• Alternative osmotic agents: lactulose or magnesium salts (use magnesium cautiously in renal impairment due to hypermagnesemia risk) 6

Stimulant laxatives are equally acceptable first-line options: 6, 1

• Senna, bisacodyl, cascara, or sodium picosulfate

Special consideration for rectal impaction: 6

• If digital rectal examination identifies full rectum or fecal impaction, suppositories and enemas are preferred first-line therapy
• Contraindications to enemas: neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal/gynecological surgery, recent anal/rectal trauma, severe colitis, toxic megacolon, undiagnosed abdominal pain, recent pelvic radiotherapy 6

Opioid-Induced Constipation (Prophylaxis Required)

All patients receiving opioid analgesics must be prescribed a concomitant laxative prophylactically unless contraindicated by pre-existing diarrhea. 6, 1

• First-line: osmotic or stimulant laxatives 6
• Avoid bulk laxatives (psyllium) for opioid-induced constipation 6, 1
• Consider combined opiate/naloxone medications to reduce constipation risk 6, 1
• For unresolved opioid-induced constipation despite laxatives, peripherally acting μ-opioid receptor antagonists (PAMORAs) may be valuable 6, 1

Step 5: Specialized Testing (Only After Failed Empiric Therapy)

Proceed to specialized functional testing only after a 1-2 week trial of fiber supplementation and over-the-counter laxatives without adequate response. 7, 3

Anorectal Function Testing (Order First if Defecatory Disorder Suspected)

Indications for anorectal manometry: 1

• Digital rectal examination suggests pelvic floor dysfunction
• Patient reports prolonged straining
• Need for perineal/vaginal pressure to evacuate
• Digital evacuation of stool required

Colonic Transit Studies (Order if Slow-Transit Suspected)

Indications for radiopaque marker study: 1, 7

• Persistent symptoms despite treatment
• Anorectal tests normal or defecatory disorder treated without symptom resolution
• Clinical presentation suggests slow-transit constipation

Step 6: Escalation for Refractory Cases

If Slow-Transit Constipation Confirmed

• Second-line agents: intestinal secretagogues (lubiprostone, linaclotide) or prokinetic agents 7
• Consider colectomy only in highly refractory cases after exhausting medical options 3

If Defecatory Disorder Confirmed

• Biofeedback therapy is the treatment of choice 3

Critical Pitfalls to Avoid

• Do not rely solely on digital rectal examination to exclude defecatory disorders—a normal exam does not rule them out 1
• Do not order excessive metabolic testing without clinical indication—this increases costs without proven benefit 1
• Do not skip structural evaluation in high-risk patients (alarm symptoms, age >50 without screening, abrupt onset) 1
• Do not proceed to specialized testing before attempting empiric fiber/laxative trial 1, 7
• Avoid liquid paraffin in bed-bound patients and those with swallowing disorders due to aspiration lipoid pneumonia risk 6
• Avoid non-absorbable soluble dietary fiber or bulk agents in non-ambulatory patients with low fluid intake due to mechanical obstruction risk 6

Special Populations

Elderly Patients

• PEG 17g/day offers efficacy with good safety profile 6, 1
• Ensure access to toilets, especially with decreased mobility 6
• Monitor closely if on concomitant diuretics or cardiac glycosides (risk of dehydration and electrolyte imbalances) 6
• Isotonic saline enemas are preferable over sodium phosphate enemas 6
• If swallowing difficulties or repeated fecal impaction present, rectal measures (enemas and suppositories) may be preferred 6

Fecal Impaction Management

• Best practice involves disimpaction (usually through digital fragmentation and extraction), followed by maintenance bowel regimen to prevent recurrence 6