Fecal Impaction
Basics
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
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
There's more to see -- the rest of this topic is available only to subscribers.
Citation
Domino, Frank J., et al., editors. "Fecal Impaction." 5-Minute Clinical Consult, 33rd ed., Wolters Kluwer, 2025. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688592/all/Fecal_Impaction.
Fecal Impaction. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2025. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688592/all/Fecal_Impaction. Accessed October 3, 2024.
Fecal Impaction. (2025). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (33rd ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688592/all/Fecal_Impaction
Fecal Impaction [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2025. [cited 2024 October 03]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688592/all/Fecal_Impaction.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC
T1 - Fecal Impaction
ID - 1688592
ED - Domino,Frank J,
ED - Baldor,Robert A,
ED - Golding,Jeremy,
ED - Stephens,Mark B,
BT - 5-Minute Clinical Consult, Updating
UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688592/all/Fecal_Impaction
PB - Wolters Kluwer
ET - 33
DB - Medicine Central
DP - Unbound Medicine
ER -