Description

Incomplete evacuation of feces leading to the formation of a large, firm, immovable mass of stool typically in the rectum or distal sigmoid colon

Epidemiology

Incidence increases with age:

• Predominant age: >70 years

Geriatric Considerations
42% of patients in a geriatric ward found to have fecal impaction (1)

• 60% of patients with fecal impaction have a history of chronic constipation (2).
• In North America, the prevalence of constipation among the general population is between 1.9% and 27.2% (3).
• Among adults, constipation is more common in women.
• 78% of all children with encopresis were found to have fecal impaction (4).
• In children, encopresis is 3× more common in boys than girls (4).

Risk Factors

• Institutionalization
• 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 East cultures), leading to rectal seed bezoars

Pediatric Considerations
Habitual neglect of defecation urge may promote impaction.

Genetics
Fecal impaction of the cecum may be seen in cystic fibrosis.

General Prevention

• Maintain adequate hydration.
• Maintain high-fiber diet (5)[C].
• Regular exercise and ambulation (5)[B]
• Establish regular, consistent toilet time using gastrocolic reflex (5)[C].
• Psyllium (6)[B]
• Periodic enemas, if indicated
• Periodic polyethylene glycol powder (MiraLax) (6)[A]
• Lactulose (6)[A]

Pathophysiology

• Age-related degenerative changes of the enteric nervous system, colonic hypomotility, and age-related anatomic changes of the lower GI tract may contribute to delayed gut transit time and decreased stool water content (7).
• The rectosigmoid colon dilates to accommodate mass of fecal material, which, in turn, is not pliable enough to pass through the disproportionately small anal canal as a result of the patient’s weak defecation effort.
• Impacted stool may exist as a single mass (stercolith) or as a composite of small, rounded fecal particles (scybalum).

Etiology

• Diet:
  • Lacking in fiber
  • Inadequate water intake
  • Low calorie
• Medication side effect (3,8):
  • 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's disease
• Metabolic:
  • Hypothyroidism
  • Hyperparathyroidism
  • Diabetes mellitus
• Electrolytes:
  • Hypokalemia
  • Hypercalcemia
  • Hypermagnesemia
• Anatomic:
  • Anorectal stenosis
  • Neoplasm
  • Megarectum
  • Painful rectal conditions inhibiting voluntary defecation (e.g., anal fissure, hemorrhoids, fistulas)
• Psychological:
  • Depression
  • Anxiety
  • Anorexia nervosa
• Immobility
• Rectal bezoars
• Pelvic floor dysfunction or dyssynergia
• Irritable bowel syndrome—constipation predominant
• Idiopathic