PHM101: Constipation in Medicine

Constipation - Definition and Epidemiology

• Constipation is a bowel disorder characterized by difficult, infrequent, or seemingly incomplete defecation that does not meet the criteria for irritable bowel syndrome.
• Definition: fewer than 3 BM's/week, > 3 days without a BM, straining > 25% of the time.
• Epidemiology: common in North America (1.9-27%), more common in females, elderly, and can be associated with serious complications.

Constipation Subtypes

• Normal transit (functional constipation): most common, difficulty evacuating, hard stool, abdominal discomfort.
• Slow transit: ↑ GI transit time.
• Disorders of defecation: pelvic floor muscle or anal sphincter dysfunction.

Normal Colonic Physiology

• Smooth muscle: parasympathetic activity responsible for peristalsis, which propels colonic contents forward.
• Colon absorbs 90% of fluid presented to it (1.5-2L).
• Defecation regulated by pelvic floor muscles and anal sphincters.

Risk Factors for Constipation

• Lifestyle: ↓ dietary fibre, inadequate fluid intake, inactivity.
• GI disorders: irritable bowel syndrome, diverticulitis, anal/rectal diseases, tumours.
• Neurogenic: spinal cord injury, CNS trauma, tumours, strokes, multiple sclerosis, Parkinson's disease.
• Endocrine disorders: hypothyroidism, diabetes (autonomic dysfunction).
• Pregnancy: hormonal changes in colonic motility, pressure of enlarged uterus on colon.
• Elderly: ↓ dietary fibre, ↓ physical activity, medications, co-morbidities (e.g., diabetes, hypothyroidism).
• Children: transition to solid food, toilet training, entry to school.

Drug-Induced Constipation

• Anticholinergics: first generation antihistamines, tricyclic antidepressants, antiparkinson drugs, oxybutynin.
• Opioids: aluminum or calcium antacids, iron preparations, calcium channel blockers, diuretics.
• All of the above drug classes can cause constipation except misoprostol.

Clinical Presentation and Diagnosis

• Clinical presentation: hard stool, difficulty defecating, sensation of incomplete defecation, bloating, distension, abdominal pain.
• Diagnosis: Rome IV criteria, history and physical exam, response to empiric therapy, routine labs and diagnostic imaging not recommended unless alarm symptoms.

Management and Prevention

• Prevention: ↑ dietary fibre, fluid intake, exercise, choice of medication, prophylactic laxatives in high-risk individuals.
• Acute treatment vs chronic prophylaxis: relevance of onset of effect in disease.
• Nonpharmacologic options: dietary fibre, fluid intake, exercise, lifestyle modifications.

Laxative Abuse

• Misperceptions about normal bowel movement frequency.
• Psychological dependency, ?physical dependency (“lazy colon”).
• Fluid and electrolyte disturbances, weight loss strategy.

Case Study

• Helen is a 73-year-old female with hard, lumpy stools, PMH: hypothyroidism, hypertension, type 2 diabetes, diabetic neuropathy.
• Could this be caused by drug therapy? Can this be treated with drug therapy?
• If so, what would be effective and safe alternatives for Helen?

Constipation

• Definition: A bowel disorder characterized by difficult, infrequent, or seemingly incomplete defecation that does not meet the criteria for irritable bowel syndrome.
• Criteria: Fewer than 3 bowel movements (BM) per week, more than 3 days without a BM, or straining more than 25% of the time.
• Prevalence: Common in North America, affecting 1.9-27% of the population, with a higher incidence in females and the elderly.

Types of Constipation

• Primary constipation: No identifiable cause.
• Secondary constipation: Due to lifestyle, medical disorders, or drugs.
• Subtypes:
  • Normal transit (functional constipation): Most common, characterized by difficulty evacuating, hard stool, and abdominal discomfort.
  • Slow transit: Increased gastrointestinal transit time.
  • Disorders of defecation: Pelvic floor muscle or anal sphincter dysfunction.

Normal Colonic Physiology

• Smooth muscle: Responsible for peristalsis, which propels colonic contents forward.
• Parasympathetic activity: Regulates peristalsis.
• Colon function: Absorbs 90% of fluid presented to it (1.5-2L).
• Defecation regulation: Regulated by pelvic floor muscles and anal sphincters.

Risk Factors for Constipation

• Lifestyle factors:
  • Lack of dietary fiber.
  • Inadequate fluid intake.
  • Inactivity.
• Neurogenic factors:
  • Spinal cord injury.
  • CNS trauma or tumors.
  • Strokes.
  • Multiple sclerosis.
  • Parkinson's disease.
• Endocrine disorders:
  • Hypothyroidism.
  • Diabetes (autonomic dysfunction).
  • Hypercalcemia.
• Pregnancy: Hormonal changes in colonic motility, pressure of enlarged uterus on colon, and use of iron and calcium supplements.
• Medications: Anticholinergics, opioids, iron, calcium channel blockers, and diuretics.

Clinical Presentation

• Hard stool, difficulty defecating, and sensation of incomplete defecation.
• Bloating, distention, and abdominal pain.
• Diagnosis: Based on Rome criteria, which include at least 2 of the following symptoms in the previous 3 months:
  • Straining > 25% of defecations.
  • Lumpy or hard stool > 25% of defecations.
  • Sensation of incomplete defecation > 25% of defecations.
  • Sensation of blockage > 25% of defecations.
  • Manual maneuvers to facilitate > 25% of defecations.
  • < 3 defecations per week.
  • Loose stools rare without use of laxatives.
• Complications: Hemorrhoids, rectal prolapse, anal fissures, bowel obstruction/impaction, and fecal incontinence (overflow diarrhea).

Diagnosis and Management

• History and physical exam: Important for diagnosis.
• Response to empiric therapy: Helpful in diagnosing constipation.
• Routine labs and diagnostic imaging: Not recommended unless alarm symptoms are present.
• Labs based on suspicion of underlying cause: e.g., TSH for hypothyroidism, Ca for hypercalcemia of malignancy.
• Flat plate abdomen: Used to diagnose structural causes.
• Barium enema and colonoscopy: Used to diagnose structural causes.
• Alarm symptoms: Unintended weight loss, hematochezia, family history of colorectal cancer or IBD, and anemia.
• Prevention: Increase dietary fiber, fluid intake, and exercise, and choose medications that do not cause constipation.
• Treatment: Correct underlying cause, use laxatives, and perform manual disimpaction if necessary.
• Non-pharmacologic strategies: Increase dietary fiber, fluid intake, and exercise, and use bowel training to prevent constipation.

Laxatives

• Types:
  • Bulk-forming laxatives (e.g., psyllium, methylcellulose).
  • Stool softeners/emollients (e.g., docusate).
  • Lubricants (e.g., mineral oil).
  • Stimulants (e.g., senna, bisacodyl, cascara).
  • Osmotic laxatives/saline cathartics (e.g., PEG, lactulose, sorbitol, magnesium).
  • Opioid receptor antagonists (e.g., naloxegol, methylnaltrexone).
  • Serotonin 5-HT4 receptor agonist (e.g., prucalopride).
  • Guanylate cyclase C receptor agonist (e.g., linaclotide).
• Administration: Oral and rectal (suppositories and enemas).