LecturePatient will present as → an elderly bed-bound patient with impaired mental function and poor fluid/fiber intake who complains of incontinence of liquid stool. He also reports rectal pressure and lower abdominal pain. The pain is cramping in quality and the patient’s abdomen is “bloated.” Digital rectal examination reveals a large amount of stool in the rectum.
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Fecal impaction is a large mass of hard, retained stool
- It generally occurs in the rectum but also may occur higher in the colon
- Classic patient: older, immobile or bedbound, dementia or neurologic disease, opioids or anticholinergics, poor fluid and fiber intake
- Overflow (paradoxical) diarrhea: liquid stool leaks around the impaction, so do a rectal exam before treating "diarrhea" in an older patient
- Complications include overflow incontinence, urinary retention, stercoral colitis (pressure ulcer of the colon wall → ischemia or perforation), and rectal prolapse
Rock hard stool in the rectal vault on examination is diagnostic of distal impaction
- Imaging is not routine; abdominal X-ray or CT if the impaction is higher up, disimpaction fails, or obstruction, perforation, or stercoral colitis is suspected (CT: fecaloma with bowel wall thickening and fat stranding)
- The elderly are at greater risk for developing chronic constipation
- Colonoscopy if there are alarm features, new constipation at age 45 or older, or the patient is not up to date on colorectal cancer screening (impaction alone is not an indication)
Abdominal X-ray done in the emergency room showing a huge fecal impaction extending from the pelvis upwards to the left subphrenic space and from the left towards the right flank, measuring over 40 cm in length and 33 cm in width. Image: Di Saverio S et al., CC BY 2.5, via Wikimedia Commons.
Distal (rectal) impaction: manual disimpaction first, then clear the colon with warm tap-water enemas (for up to 3 days) or oral PEG-electrolyte solution once obstruction is excluded
- More proximal impaction or failed disimpaction → water-soluble contrast enema under fluoroscopy (excludes obstruction and helps clear stool); sigmoidoscopy can break up stool beyond the finger
- Avoid sodium phosphate (Fleet) enemas in older adults (hyperphosphatemia, hypocalcemia, kidney injury) and soap-suds enemas (colitis); use magnesium laxatives with caution in kidney disease
- Prevent recurrence: daily PEG 3350 for a stool at least every other day, toileting after meals, a bisacodyl or glycerin suppository if no bowel movement in 2 days, and stop constipating drugs when possible
- Bedbound or dementia: extra fiber can make it worse; scheduled enemas once or twice weekly can help
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Question 1 |
An 84-year-old bedbound nursing home resident with dementia, who takes oxycodone and oxybutynin, has had small amounts of liquid stool leaking several times a day for 4 days. He has crampy lower abdominal pain and a distended abdomen. Which of the following is the most likely cause of his liquid stool?
Clostridioides difficile colitis Hint: C. difficile follows antibiotic exposure and causes frequent watery stools with fever and leukocytosis; always do a rectal exam first in an older immobile patient. | |
Fecal impaction with overflow | |
Ischemic colitis Hint: Ischemic colitis causes sudden crampy pain followed by bloody diarrhea. | |
Laxative overuse Hint: He has no laxative exposure; his opioid and anticholinergic both cause constipation. | |
Viral gastroenteritis Hint: Viral gastroenteritis is acute, with vomiting and diarrhea, and is not tied to immobility and constipating drugs. |
Question 1 Explanation:
Older, immobile patients with dementia who take constipating drugs (opioids, anticholinergics) are at high risk for fecal impaction. Liquid stool can leak around the hard mass of stool (overflow or paradoxical diarrhea), so a digital rectal exam should be done before treating "diarrhea" in this setting. Treating it as diarrhea with antidiarrheals would make the impaction worse.
Question 2 |
An 80-year-old woman with Parkinson disease has rectal pressure, cramping lower abdominal pain, and no bowel movement for 6 days. Vital signs are normal, and the abdomen is mildly distended but soft without peritoneal signs. Which of the following is the most appropriate initial diagnostic step?
Abdominal CT with contrast Hint: CT is reserved for impaction higher in the colon, failed disimpaction, or suspected obstruction, perforation, or stercoral colitis. | |
Barium enema Hint: Barium can harden and worsen an impaction; a water-soluble contrast enema is used only if disimpaction fails. | |
Colonoscopy Hint: Colonoscopy is not the first step; it is done later if there are alarm features or screening is not current. | |
Digital rectal examination | |
Upright abdominal radiograph Hint: Plain films are not needed when the rectal exam shows a rectal impaction; they are used if the exam is unrevealing or complications are suspected. |
Question 2 Explanation:
A digital rectal examination is the first and usually the only test needed: it shows a mass of hard stool in the rectal vault. Imaging (abdominal X-ray or CT) is reserved for impaction higher in the colon, failed disimpaction, or concern for obstruction, perforation, or stercoral colitis.
Question 3 |
A 78-year-old man in a skilled nursing facility has a large amount of rock-hard stool in the rectal vault on digital rectal examination. He has no fever, peritoneal signs, or signs of obstruction. Which of the following is the most appropriate initial treatment?
Manual disimpaction | |
Milk of magnesia Hint: Oral laxatives work poorly against a hard rectal mass and can cause cramping; they are used after disimpaction. | |
Nasogastric tube placement Hint: A nasogastric tube is not used for a distal colonic or rectal impaction. | |
Oral sodium phosphate Hint: Sodium phosphate can cause severe hyperphosphatemia, hypocalcemia, and kidney injury in older adults and should be avoided. | |
Sigmoid colectomy Hint: Surgery is only for complications such as perforation or ischemia. |
Question 3 Explanation:
Distal (rectal) fecal impaction is treated first with manual disimpaction: the hard stool is broken up and removed with a gloved, lubricated finger. The rest of the colon is then cleared with warm tap-water enemas for up to 3 days or with an oral PEG-electrolyte solution once obstruction is excluded, followed by a daily maintenance regimen to prevent recurrence.
Question 4 |
After manual disimpaction, an 86-year-old woman with chronic kidney disease stage 3b needs her colon cleared. Which of the following agents carries the greatest risk of hyperphosphatemia, hypocalcemia, and acute kidney injury in this patient?
Bisacodyl suppository Hint: Bisacodyl suppositories are safe and useful when there has been no bowel movement for 2 days. | |
Glycerin suppository Hint: Glycerin suppositories are safe and help trigger a bowel movement. | |
Oral polyethylene glycol Hint: PEG is the preferred osmotic laxative in older adults and is safe in kidney disease. | |
Sodium phosphate enema | |
Warm tap-water enema Hint: Warm tap-water enemas are the preferred enema after disimpaction. |
Question 4 Explanation:
Sodium phosphate (Fleet) enemas and oral sodium phosphate can cause severe hyperphosphatemia, hypocalcemia, hypokalemia, dehydration, and acute kidney injury, especially in older adults and patients with kidney disease, so they should be avoided. Soap-suds enemas can cause colitis, and magnesium-containing laxatives should be used with caution in kidney disease. Warm tap-water enemas or PEG are preferred.
Question 5 |
A 79-year-old man has recovered after manual disimpaction and colon cleansing for a fecal impaction. He takes no opioids now and can walk with a walker. Which of the following is the most appropriate regimen to prevent recurrence?
Daily docusate Hint: Docusate is a weak stool softener that is not recommended because it does not prevent constipation or impaction. | |
Daily loperamide Hint: Loperamide slows the bowel and would cause another impaction. | |
Daily polyethylene glycol 3350 with scheduled toileting | |
Twice-weekly sodium phosphate enemas Hint: Sodium phosphate enemas are avoided in older adults because of electrolyte and kidney risks. | |
Weekly magnesium citrate Hint: Weekly magnesium citrate does not keep stool moving daily and risks hypermagnesemia in older adults. |
Question 5 Explanation:
After disimpaction, recurrence is prevented with a daily osmotic laxative, usually polyethylene glycol 3350, aiming for a soft stool at least every other day, plus toileting after meals. A bisacodyl or glycerin suppository is added if there is no bowel movement in 2 days, and constipating drugs are stopped when possible. In bedbound patients with dementia, extra fiber can worsen impaction, and scheduled enemas once or twice weekly may help.
There are 5 questions to complete.
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References: Merck Manual · UpToDate