What is the step‑by‑step approach to evaluate and manage chronic constipation in an adult, ruling out secondary causes (e.g., hypothyroidism, hypercalcemia, medication effect, obstruction) and using diet, fluid, exercise, osmotic laxatives, stimulant laxatives, and prescription secretagogues?

Chronic Constipation Management in Adults

Initial Evaluation: Rule Out Secondary Causes

Begin by discontinuing constipating medications if feasible, and perform a focused digital rectal examination assessing pelvic floor motion during simulated evacuation before any further testing. 1

Essential History and Physical Examination Elements

• Assess defecation patterns, stool consistency (Bristol scale), symptoms of dyssynergic defecation (incomplete evacuation, straining, anorectal blockage), and alarm symptoms (blood in stool, unintended weight loss, acute onset in older patients). 1, 2

• Perform digital rectal examination in left lateral position: observe perineal descent during simulated evacuation, assess resting and squeeze sphincter tone, evaluate puborectalis contraction, and instruct patient to "expel my finger" to assess defecatory function. 1

• A normal digital rectal examination does NOT exclude pelvic floor dysfunction—specialized testing may still be needed. 1

Laboratory Testing: Less is More

• Order only a complete blood count in the absence of other symptoms—this is sufficient. 1

• Do NOT routinely order metabolic panels (TSH, calcium, glucose) for chronic constipation unless other clinical features warrant it, as their diagnostic utility is low and not cost-effective. 1

• Colonoscopy is NOT indicated unless: patient has alarm symptoms, abrupt onset of constipation, age >50 without prior colorectal cancer screening, or is overdue for screening. 1, 3

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Step-by-Step Treatment Algorithm

Step 1: Lifestyle Modifications (First-Line for All Patients)

• Ensure adequate fluid intake, regular moderate exercise as tolerated, and immediate toileting in response to urge to defecate. 1

• Increase dietary fiber intake through food sources, but avoid supplemental medicinal fiber (psyllium, bran) as it is ineffective and may worsen constipation in patients with inadequate fluid intake or low mobility. 1

Step 2: Osmotic Laxatives (First-Line Pharmacotherapy)

Polyethylene glycol (PEG) 17 grams in 8 oz water twice daily is the preferred first-line agent. 1, 4

• PEG is superior to other osmotic laxatives (lactulose, magnesium salts) due to better efficacy, tolerability, and safety profile, particularly in elderly patients. 1

• Alternative osmotic agents include: lactulose 30-60 mL twice to four times daily, sorbitol 30 mL every 2 hours × 3 then as needed, or magnesium hydroxide 30-60 mL daily to twice daily. 1

• Avoid magnesium-based laxatives in patients with renal dysfunction due to hypermagnesemia risk. 1

Step 3: Stimulant Laxatives (Second-Line)

If osmotic laxatives fail, add bisacodyl 10-15 mg daily to three times daily OR senna 2-3 tablets twice to three times daily, with goal of one non-forced bowel movement every 1-2 days. 1

• Do NOT use docusate (stool softener)—multiple studies show no benefit when added to stimulant laxatives. 1

• Common pitfall: Bisacodyl fails when fecal impaction is present—always perform digital rectal examination first, as oral laxatives cannot work with a loaded rectum. 5

• If oral bisacodyl fails and moderate fecal burden is present, switch to bisacodyl suppository 10 mg rectally. 5

Step 4: Combination Therapy

Combine osmotic and stimulant laxatives if monotherapy with either class fails—this is often successful where single agents are not. 5, 4

• Reassess for impaction or obstruction if constipation persists despite combination therapy. 1

• Rule out hypercalcemia, hypokalemia, hypothyroidism, and diabetes mellitus, as these conditions cause laxative-refractory constipation. 1, 5

Step 5: Prescription Secretagogues (Third-Line)

If combination laxatives fail, add intestinal secretagogues: 3, 4

• Linaclotide (FDA-approved for chronic idiopathic constipation): guanylate cyclase-C agonist that stimulates chloride secretion and increases luminal fluid. 1

• Lubiprostone (FDA-approved for chronic idiopathic constipation): chloride channel activator. 1

• Plecanatide: another guanylate cyclase-C agonist option. 4

Step 6: Prokinetic Agents (Refractory Cases)

Prucalopride (selective 5-HT4 receptor agonist) is recommended as second-line treatment in refractory chronic constipation patients who fail laxatives. 1, 6, 4

• Prucalopride is effective and well-tolerated, with transient headache and gastrointestinal symptoms being the most common side effects. 1

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Special Considerations

Opioid-Induced Constipation (OIC)

Opioid-induced constipation requires prophylactic treatment from the start—patients do NOT develop tolerance to constipation. 1

• Prophylaxis: Stimulant laxative OR PEG 17 grams twice daily with adequate fluid intake. 1

• Do NOT use bulk laxatives (psyllium) for OIC—they are ineffective and contraindicated. 1

• If standard laxatives fail in OIC, use peripherally acting μ-opioid receptor antagonists (PAMORAs): methylnaltrexone 0.15 mg/kg subcutaneously every other day (max once daily), naloxegol, or naldemedine. 1

• PAMORAs are contraindicated in mechanical bowel obstruction. 1

• Consider opioid rotation to fentanyl or methadone, or combination opioid/naloxone preparations (oxycodone + naloxone) which have lower constipation risk. 1

Fecal Impaction

If impaction is present (identified by digital rectal examination), oral laxatives will fail. 5

• Treatment: Digital fragmentation and extraction of stool (pre-medicate with analgesic ± anxiolytic), followed by glycerine suppository ± mineral oil retention enema. 1

• Then use bisacodyl suppository 10 mg rectally daily to twice daily, or tap water enema until clear. 1

• Avoid rectal suppositories/enemas in neutropenic or thrombocytopenic patients. 1

Elderly Patients

PEG 17 grams daily offers the best efficacy and safety profile in elderly patients. 1

• Ensure toilet access, especially with decreased mobility, and educate patients to attempt defecation twice daily (30 minutes after meals), straining no more than 5 minutes. 1

• Avoid liquid paraffin in bed-bound patients or those with swallowing disorders due to aspiration pneumonia risk. 1

• Use isotonic saline enemas rather than sodium phosphate enemas in elderly due to electrolyte disturbance risk. 1

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When to Refer for Specialized Testing

Refer to gastroenterology for anorectal manometry, balloon expulsion test, and colonic transit studies if patients fail first-line osmotic laxatives and second-line stimulant laxatives. 1, 3

• Anorectal testing identifies defecatory disorders (pelvic floor dysfunction), which respond to biofeedback therapy rather than escalating laxatives. 1, 7, 6

• Colonic transit studies identify slow-transit constipation, which may require prokinetic agents or, in highly selected refractory cases, colectomy. 7, 4