Fecal Impaction

How fecal impaction happens

When stool stays in the colon, water is absorbed and it becomes harder. If it is not passed, more stool accumulates behind it, forming a firm mass that the rectum cannot push out. The rectum may stretch and lose sensation, so the urge to have a bowel movement fades, making the problem worse.

Causes and risk factors

• Long-standing constipation, see chronic constipation.
• Medicines: opioids, anticholinergics, some antidepressants, iron and calcium supplements, antacids containing aluminum or calcium, and calcium channel blockers.
• Reduced mobility: bed rest, hospital stays, frailty.
• Low fluid and fiber intake.
• Neurological conditions: dementia, Parkinson's disease, stroke, multiple sclerosis, spinal cord injury.
• Ignoring the urge to have a bowel movement, often due to pain from hemorrhoids or an anal fissure.
• Metabolic causes: hypothyroidism, high calcium, low potassium, diabetes.
• After barium X-ray studies.

Symptoms

• no bowel movement for several days, or passing only small, hard pieces
• a feeling of fullness or pressure in the rectum and straining without result
• abdominal cramps, bloating and swelling
• loss of appetite, nausea and vomiting
• overflow diarrhea: watery stool leaking around the impacted mass, sometimes causing soiling. This is often misinterpreted as diarrhea and wrongly treated with anti-diarrhea medicines
• in older adults: confusion, agitation, falls, or urinary retention, sometimes as the only signs
• back pain or rectal bleeding from irritation

Diagnosis

• Digital rectal exam: a gloved finger detects hard stool in the rectum. This confirms most cases.
• Abdominal X-ray: shows stool higher in the colon and checks for bowel obstruction or a dilated colon.
• CT scan: if complications are suspected.
• Blood tests: thyroid function, calcium, potassium and kidney function.
• Colonoscopy: later, if there are concerning features such as weight loss or a change in bowel habit in older adults, to rule out a tumor.

Treatment

Clearing the impaction

• Enemas: warm water, saline, mineral oil, or phosphate enemas soften and loosen the stool. Phosphate enemas are avoided in people with kidney disease.
• Suppositories: glycerin or bisacodyl.
• Manual disimpaction: a clinician gently breaks up and removes the stool with a gloved, lubricated finger, sometimes after a local anesthetic gel or sedation.
• Oral laxatives: polyethylene glycol (PEG) at higher doses can clear impaction higher in the colon, once low rectal impaction has been relieved.
• Rarely, removal under anesthesia or surgery for very large or complicated impactions.

After clearing

• a regular laxative, such as polyethylene glycol, to keep stools soft
• adequate fluids and fiber as tolerated
• a regular toilet routine, ideally after meals, using a footstool to raise the knees
• reviewing constipating medicines; for people on opioids, a laxative should be started at the same time

Complications

• bowel obstruction
• stercoral ulcer: pressure damage to the bowel wall, which can bleed or, rarely, perforate
• fecal incontinence from overflow or a stretched rectum
• urinary retention and urinary tract infections
• in frail people, delirium and dehydration

Prevention

• Drink enough fluids so that urine is pale yellow.
• Eat fiber-rich foods, increasing fiber gradually. Fiber supplements need extra fluid.
• Stay as active as possible.
• Respond promptly to the urge to go.
• Ask about a preventive laxative if you take opioids or other constipating medicines.
• In care settings, track bowel movements so constipation is caught early.

Frequently asked questions

What are the signs of fecal impaction?

Signs include not having a bowel movement for several days, rectal pressure, straining without passing stool, abdominal cramps and bloating, nausea, and sometimes leaking watery stool. Older adults may become confused or agitated.

Can you have diarrhea with fecal impaction?

Yes. Liquid stool from higher in the bowel can leak around the hard mass, causing what looks like diarrhea or soiling. This overflow diarrhea should not be treated with anti-diarrhea medicines, which make the impaction worse.

How is impacted stool removed?

Enemas or suppositories soften and loosen the stool. If that is not enough, a clinician removes it manually with a gloved finger. Oral laxatives then clear remaining stool and keep the bowels moving to prevent recurrence.

Can fecal impaction resolve on its own?

Rarely. Once stool is hard and impacted, it usually needs enemas, suppositories or manual removal. Mild constipation can resolve with fluids and laxatives, but suspected impaction should be assessed by a healthcare professional.