Fecal Impaction

Background

• Fecal impaction occurs when thickened, hardened fecal matter in the rectum or colon cannot be evacuated spontaneously. It is most commonly seen in elderly or pediatric patients as a complication of chronic constipation.
• Fecal impaction may affect up to 40% of older patients in assisted living or hospital settings, and is a frequent cause of emergency department visits for nursing home residents.
• Risk factors for impaction include immobility or bed-bound status, medications that cause hypomotility, anatomic conditions, such as anal fissure, past anal surgery, or Hirschsprung disease, and neuropsychiatric conditions, such as dementia.
• Patients typically present with abdominal pain and bloating, difficulty evacuating bowels, and/or rectal discomfort. Patients may report diarrhea or fecal incontinence with the passage of soft or watery stool due to seepage around the fecal mass.
• Elderly patients or patients with dementia may present with increased confusion or agitation, and/or autonomic dysreflexia with hemodynamic instability.
• Fecal impaction can lead to damage of the intestinal wall, including ischemia, necrosis, ulceration, perforation, and peritonitis.

Evaluation

• Consider imaging with acute abdominal x-ray series, including upright kidney ureter bladder (KUB), or computed tomography (CT) scanning to assess for intraluminal feces, signs of obstruction, and to rule out a perforation if suspected.
  • Dilated loops of bowel with air-fluid levels and fecaloma or large masses of fecal matter in the colon or rectum are consistent with fecal impaction.
  • Free air may be seen under the diaphragm in upright x-rays in patients with a perforation.
  • In children and pregnant women, consider ultrasound for evaluation of acute abdominal pain as alternative to x-ray or CT scanning, to reduce radiation exposure.
• Rule out other causes of lower abdominal pain with or without bowel symptoms, such as appendicitis, diverticulitis, ovarian cancer, or ovarian cyst rupture. Rule out other potential causes of obstruction, such as small bowel obstruction, colorectal cancer, or a foreign body.

Management

• If a perforation, peritonitis, or massive hemorrhage is suspected, perform abdominal surgery.
• Base the choice of methods of disimpaction and clean out on individual clinical factors, including whether or not there is structural obstruction, positioning of the fecal matter (proximally or distally located), and the age, mobility status, and aspiration risk of the patient.
• For most infants and children, oral treatment will be adequate. Options include polyethylene glycol (PEG) electrolyte solution 1-1.5 g/kg/day orally for 3-6 days, mineral oil 15-30 mL/year of age (maximum 240 mL/day), or magnesium citrate dose 1 ounce (30 mL)/year of age orally for 2-3 days (maximum 10 ounces [300 mL]/day).
  • Though rarely needed in infants < 1 year old, a glycerin suppository of 1.2 g rectally can be used once.
  • Enemas with phosphate soda (6 mL/kg up to 135 mL), saline, or mineral oil may be used for more rapid treatment in children ≥ 2 years old.
  • See also Constipation in children.
• For adults with evidence of complete obstruction and a distally located impaction, consider manual disimpaction and/or a rectal suppository or enema for fecal clean out.
  • Consider stimulant suppositories, such as bisacodyl or glycerin, before an enema, if possible, as a suppository is less invasive.
  • Consider options for enemas in adults such as warm water with sorbitol and docusate sodium syrup, or mineral oil enema.
• For adult patients with proximally located fecal matter without obstruction, plus good mobility status and access to toileting facilities, consider an oral osmotic laxative for fecal clean out.
  • Consider PEG (macrogol) with or without electrolytes as the first-line option, with either PEG 3350 [MiraLAX]) 17 g in 4-8 ounces of water every 15 minutes until patient passes stool or 8 glasses consumed, or PEG with electrolytes (GoLYTELY or NuLYTELY) 1-2 L once daily for 1-2 days.
  • Alternatives include lactulose 15-30 mL (10-20 g lactulose) orally once daily for 24-48 hours or magnesium citrate 30-60 mL orally with 4 ounces of clear liquids, every 4-8 hours.
• Recurrence of impaction is common, so after disimpaction and clean out, assess for underlying causes and risk factors, if not already known, and advise maintenance therapy for chronic constipation unless a reversible cause is identified.
  • For adults, options include PEG 17 g/day or lactulose 10-20 g/day for maintenance.
  • For children, PEG with or without electrolytes is recommended as first line for use as maintenance therapy starting with a dose of 0.4 g/kg/day and adjusted according to the clinical response. (See also Constipation in children.)
• For opioid-induced impaction, advise the same initial management as for fecal impaction due to other causes. For maintenance therapy, consider conventional therapies for constipation such as stool softeners or osmotic agents, and opioid receptor antagonists (methylnaltrexone, alvimopan, or naloxone) or prucalopride. (See also Constipation and other gastrointestinal effects in Opioids for chronic noncancer pain.)