Fecal Impaction

Description

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

Epidemiology

Incidence
Incidence increases with age.

• Predominant age: >70 years

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

Prevalence

• 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

Genetics
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]