Common Causes of Constipation
Constipation is primarily caused by medications (especially opioids), inadequate fluid and fiber intake, reduced physical activity, and various medical conditions including metabolic disorders and neurological diseases. 1
Primary Causes
Medication-Related Causes
Opioid analgesics: Most commonly associated with constipation, affecting nearly all patients on opioids 1
- Tolerance to this side effect does not develop over time
- Acts through μ-opioid receptors in the gastrointestinal tract
Other common constipating medications 1, 2:
- Anticholinergic drugs (antidepressants, antispasmodics, phenothiazines)
- 5-HT3 receptor antagonist antiemetics
- Vinca alkaloids (chemotherapy agents)
- Antacids (particularly aluminum-containing)
- Diuretics (OR = 1.7, PAR = 5.6%)
- Antihistamines (OR = 1.8, PAR = 9.2%)
- Antispasmodics (OR = 3.3, PAR = 11.6%)
- Anticonvulsants (OR = 2.8, PAR = 2.5%)
Lifestyle and Dietary Factors
- Inadequate fluid intake leading to dehydration 3
- Low dietary fiber consumption 4, 5
- Reduced physical activity 4
- Ignoring the urge to defecate 1
- Lack of privacy when toileting 1
Medical Conditions
Metabolic disorders 1:
- Hypercalcemia
- Hypokalemia
- Hypothyroidism
- Diabetes mellitus
- Uremia
Structural issues 1:
- Abdominal or pelvic masses
- Radiation fibrosis
- Bowel obstruction
- Primary neurological diseases (strongly associated but account for few cases)
- Autonomic neuropathy
Pathophysiology of Constipation
Constipation represents a disruption of normal bowel function through several mechanisms 1:
- Disruption of normal motility: Slowed transit time through the colon
- Excessive dryness of fecal content: Longer stool remains in colon, the drier it becomes
- Diminished perception of rectal distension: Loss of urge to defecate
- Dysfunction of the rectal sphincter: Difficulty with evacuation
Special Populations
Elderly patients: Five times more prone to constipation than younger people due to 1:
- Polypharmacy
- Reduced mobility
- Reduced hydration
- Reduced urge to defecate
- Prevalence rates of 51-55% in older cancer patients
Cancer patients: 40-90% prevalence, higher in those on opioid therapy 1
Clinical Impact
Constipation can lead to significant complications if untreated 1:
- Nausea and vomiting
- Hemorrhoids and anal fissures
- Bowel obstruction
- Urinary retention
- Psychological distress and anxiety
Prevention Strategies
- Maintain adequate fluid intake 3
- Ensure sufficient dietary fiber (20-25g daily) 4, 5
- Regular physical activity within patient limitations 4
- Prophylactic laxative therapy when starting opioids 1
Common Pitfalls
- Failing to recognize medication-induced constipation, especially with opioids
- Not addressing underlying metabolic disorders
- Insufficient attention to hydration status
- Overlooking the impact of reduced mobility
- Inadequate prophylaxis when starting constipating medications
Understanding these causes allows for targeted prevention and treatment strategies to reduce the significant burden of constipation on patients' quality of life.