Fecal Impaction



Incomplete evacuation of feces leading to the formation of a large, firm, immovable mass of stool in the rectum or distal sigmoid colon with resultant partial or complete obstruction


Incidence increases with age.

  • Predominant age: >70 years

Geriatric Considerations
50% of geriatric ward patients have fecal impaction (1).


  • 70% of patients with fecal impaction have a history of chronic constipation (1).
  • The prevalence of constipation in the general population is approximately 30% (2).
  • Constipation is more common in females, non-whites, and with lower socioeconomic status (2).

Etiology and Pathophysiology

  • Age-related degenerative changes of the enteric nervous system and colonic smooth muscle myopathy lead to colonic hypomotility.
  • Age-related anatomic changes of the lower GI tract contribute to delayed gut transit time and decreased stool water content.
  • Increased rectal compliance and abnormal rectal sensation result in a dilated rectosigmoid colon that accommodates fecal material which is not pliable enough to pass through the anal canal.
  • Impacted stool may exist as a single mass (stercolith) or as a composite of small, rounded fecal particles (scybalum). Fecaloma (fecalith) is an extreme form, which presents as a hardened, often calcified, stool mass.
  • Poor diet
    • Inadequate fiber, water, and caloric intake all contribute to impaction.
  • Medication side effect (3)
    • Stimulant laxatives
    • Opiate analgesics
    • Anticholinergics
    • Diuretics
    • Calcium channel blockers
    • Aluminum (sucralfate, antacids)
    • Iron
    • NSAIDs
  • Neurogenic disorders
    • Hirschsprung disease
    • Chagas disease
    • Autonomic neuropathy
    • Multiple sclerosis
    • Spinal cord injury
    • Cauda equina
    • Parkinson disease
    • Alzheimer disease
  • Metabolic disease
    • Hypothyroidism
    • Hyperparathyroidism
    • Diabetes mellitus
  • Electrolyte disturbances
    • Hypokalemia
    • Hypercalcemia
    • Hypermagnesemia
  • Anatomic abnormalities
    • Anorectal stenosis
    • Neoplasm
    • Megarectum
    • Painful rectal conditions inhibiting voluntary defecation (anal fissure, hemorrhoids, fistulas)
  • Psychological comorbidities
    • Depression
    • Anxiety
    • Anorexia nervosa
  • Immobility
  • Pelvic floor dysfunction or dyssynergia
  • Irritable bowel syndrome, constipation predominant. Fecal impaction of the cecum may be seen in cystic fibrosis.
  • Idiopathic

In the absence of known syndrome (e.g., Hirschsprung disease), there is no known genetic link.

Risk Factors

  • Institutionalization
  • Prior history of fecal impaction
  • Constipation
  • Psychogenic illness
  • Immobility, inactivity
  • Pica
  • Chronic renal failure
  • Urinary incontinence
  • Cognitive decline, disability
  • Heavy metal ingestion or exposure
  • Poor toileting habits
  • Excessive seed consumption (common in Middle Eastern cultures), leading to rectal seed bezoars
  • Medication (opioids)

Pediatric Considerations
Habitual neglect of urge to defecate may promote impaction.

General Prevention

  • Maintain adequate hydration.
  • Maintain high-fiber diet (4)[C].
  • Regular exercise and ambulation (4)[B]
  • Establish regular toilet time leveraging gastrocolic reflex to promote defecation after meals (4)[C].
  • Psyllium (4)[B]
  • Periodic enemas, if indicated
  • Periodic polyethylene glycol powder (MiraLAX) (5)[A]
  • Lactulose (5)[A]

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