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Constipation

Basics

  • Definition: Unsatisfactory defecation with infrequent (<3/week), hard stools, straining, prolonged effort, incomplete evacuation, or bloating.

  • Geriatric considerations:
    New-onset constipation after age 50 years is a red flag for colorectal neoplasms.
    Use warm water enemas instead of sodium phosphate enemas due to electrolyte and cardiac risks.

  • Pediatric considerations:
    Hirschsprung disease is a key consideration in newborn/infant constipation (25% of newborn obstructions).

  • Pregnancy considerations:
    Common due to progesterone effects, uterine pressure, iron supplements, decreased activity.

Epidemiology

  • More common in children and elderly.
  • Female predominance (2:1).
  • Nonwhites > whites.
  • 5 million office visits, 100,000 hospitalizations yearly.
  • Prevalence: 16% adults >18 yrs, 33% adults >60 yrs; 3% pediatric visits.

Etiology and Pathophysiology

  • Defecation reflex involves rectal distension and relaxation/contraction of anal sphincters and abdominal muscles.
  • Gastrocolic reflex initiates urge postprandially.

Risk Factors

  • Extremes of age, female sex, polypharmacy, sedentary lifestyle.
  • Low-fiber diet, inadequate fluids.
  • Increased stress or abuse history.

General Prevention

  • High-fiber diet, adequate hydration, exercise.
  • Train to obey defecation urge.

Associated Conditions

  • Debilitation, dehydration, hypothyroidism, electrolyte disturbances (hypokalemia, hypercalcemia).

Diagnosis

  • Red flags:
    New onset >50 yrs, fever, nausea/vomiting, blood in stool, weight loss >4.5 kg, change in bowel habits, family history of colon cancer or IBD, abdominal pain, anemia, neurologic deficits.

  • History:
    Onset, frequency, straining, sensation of incomplete evacuation, manual maneuvers, diet, meds, abuse history, opioid use, neurologic/systemic illness.

  • Assessment tools:
    Bristol Stool Form Scale, Rome IV criteria (≥2 of 6 symptoms for ≥12 weeks), Bowel Function Index (opioid-induced constipation).

  • Physical Exam:
    Vital signs, abdominal exam (scars, distention, bowel sounds, tenderness), gynecologic exam, anorectal exam (fissures, hemorrhoids, prolapse), neurologic exam.

  • Differential diagnosis:
    Primary constipation (normal transit, slow transit, pelvic floor dysfunction), secondary causes (endocrine, metabolic, mechanical, neurologic, medication-induced).

Diagnostic Tests

  • CBC (screen for anemia).
  • Electrolytes, calcium, creatinine, glucose, TSH as indicated.
  • Colonoscopy if red flags or screening indicated.
  • Anorectal manometry, balloon expulsion, defecography for refractory cases.

Treatment

  • General measures:
    Stop meds causing constipation.
    Increase fluids and soluble fiber (25-30 g/day).
    Encourage regular toileting, exercise.

  • Medications:

  • First line:
    Bulking agents (psyllium, methylcellulose, polycarbophil, wheat dextrin).
    Osmotic laxatives (polyethylene glycol, lactulose, sorbitol, magnesium salts).
  • Second line:
    Stimulants (senna, bisacodyl).
    Suppositories (glycerin, sodium phosphate, bisacodyl).
    Enemas (saline).
  • Prescription agents:
    Lubiprostone, prucalopride, guanylate cyclase-C agonists (linaclotide, plecanatide).

  • Opioid-induced constipation: trial laxatives, then peripherally acting µ-opioid receptor antagonists (methylnaltrexone, naloxegol, naldemedine).

  • Additional therapies:
    Biofeedback, behavioral therapy, acupuncture (limited evidence).

  • Surgery:
    Rare, for anatomical abnormalities or refractory cases.

Admission/Nursing Considerations

  • Toxic megacolon, manual disimpaction in chronic cases.

Ongoing Care

  • Gradual increase of fiber with attention to gas/bloating.
  • Encourage liberal fluids.
  • Bowel training: best time post-breakfast.

Patient Education

  • Mild constipation is common and manageable.
  • Encourage bowel routine and diet changes.

Prognosis

  • Mild constipation responds to simple measures; chronic may be lifelong nuisance.
  • No evidence stimulant laxatives cause dependence.

Complications

  • Volvulus, toxic megacolon, acquired megacolon.
  • Fluid/electrolyte disturbances with laxative abuse.
  • Stercoral ulcers, fissures, prolapse, hemorrhoids.

Clinical Pearls:
- New constipation after age 50 warrants evaluation for neoplasms.
- Hirschsprung disease important in pediatric constipation.
- Bulking agents plus hydration are first-line treatments in most cases.