Constipation
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Basics

A group of syndromes with similar findings that include unsatisfactory defecation characterized by infrequent stools, difficult stool passage, or both. Characteristics include <3 bowel movements a week, hard stools, excessive straining, prolonged time spent on the toilet, a sense of incomplete evacuation, and abdominal discomfort/bloating.

Description

  • System(s) affected: Gastrointestinal (GI)
  • Synonym(s): Obstipation

Geriatric Considerations
Increased incidence of colorectal neoplasms with age may be associated with constipation; thus, new onset of constipation after 50 years of age is considered a “red flag.”

Pediatric Considerations
Consider Hirschsprung disease (absence of colonic ganglion cells): 25% of all newborn intestinal obstructions, milder cases diagnosed in older children with chronic constipation, abdominal distension, decreased growth. 5:1 Male:Female ratio. Associated with inherited conditions such as Down syndrome.

Epidemiology

  • Predominant age: May affect all ages, but more pronounced in children and elderly
  • Predominant sex: Female > Male (2:1)
  • Nonwhites > Whites
Incidence
  • 5 million office visits annually
  • 100,000 hospitalizations

Prevalence
~15% of population affected

Risk Factors

  • Extremes of life (very young and very old)
  • Polypharmacy
  • Sedentary lifestyle or condition
  • Improper diet and inadequate fluid intake

Genetics
Unknown, but condition may be familial

General Prevention

High-fiber diet, adequate fluids, exercise, and bowel training to “obey the urge” to defecate are useful preventive strategies.

Pathophysiology

  • As food leaves the stomach, the ileocecal valve relaxes (gastroileal reflex) and chyme enters the colon (1–2 L/d). Peristaltic contractions move the chyme through the colon into the rectum. In the colon, sodium is actively absorbed in exchange for potassium and bicarb: Water follows because of the generated osmotic gradient. The chyme is converted into feces (200–250 mL).
  • Normal transit time for a meal to reach the cecum is 4 hours, and the pelvic colon 8 hours later. Transit then slows to the anus. Rectal distention initiates the defecation reflex.
  • Defecation follows as a reflex that can be inhibited by voluntarily contracting the external sphincter or facilitated by straining to contract the abdominal muscles while voluntarily relaxing the anal sphincter. The urge to defecate occurs as rectal pressures increase. Distention of the stomach by food also initiates rectal contractions and a desire to defecate.

Etiology

  • Primary constipation:
    • Slow colonic transit time (13%)
    • Pelvic floor/anal sphincter dysfunction (25%)
    • Functional: Normal transit time and sphincter function, yet problems (bloating, abdominal discomfort, perceived difficulty going, presence of hard stools) (69%)
  • Secondary constipation:
    • Irritable bowel syndrome (IBS)
    • Endocrine dysfunction (diabetes mellitus, hypothyroid)
    • Metabolic disorder (increased calcium, decreased potassium)
    • Mechanical (obstruction, rectocele)
    • Pregnancy
    • Neurologic disorders (Hirschsprung, multiple sclerosis, spinal cord injuries)
  • Medication effect:
    • Anticholinergic effects (antidepressants, narcotics, antipsychotics)
    • Antacids (calcium, aluminum)
    • Calcium channel blockers

Commonly Associated Conditions

  • Debility, either general as in the aged or that imposed by specific underlying illness
  • Dehydration
  • Hypothyroidism
  • Hypokalemia
  • Hypercalcemia

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