Constipation

Chelsie Sievers

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Background

• Definition: presence of lumpy/hard stools, straining, use of digital maneuvers, sensation of incomplete evacuation, frequency \<3 BM per week.
• Common etiologies: opioid-induced, medications (anti-depressants, iron, anticholinergics) hypothyroidism, hypokalemia, pregnancy, IBS, neurogenic (trauma, MS, Parkinson disease, diabetes, autonomic dysregulation).
• Always think about risk of obstruction (prior abdominal surgeries, oncology history or risk for GI/GU malignancies, history of IBD/Crohn’s).

Evaluation

• Evaluate etiologies plus lifestyle factors (low fiber intake, low fluid intake, reduced mobility, acute illness)
• Clinical diagnosis, no need for imaging unless concerned for obstruction → KUB/ CT
• BMP + Mg to evaluate electrolytes, consider TSH if chronic
• Rectal exam to exclude rectal mass or fecal impaction (constipation + diarrhea doesn’t exclude impaction/obstruction. Overflow around mass = encoparesis)

Management

• Stop or minimize offending medications if possible
• Optimize lifestyle factors: out of bed, walking hallways, increase fluid intake, + cup of coffee if appropriate.
• Escalating pathway: ensure meds are scheduled not PRN
  • MiraLAX (PEG) 17g BID (can give TID) + Senna nightly (can > increase to BID and/or 2 tabs) → Bisacodyl suppository → enema > (tap water or SMOG) → stronger osmotic laxative (lactulose > 20mg once, Mag-citrate, Golytely) → escalate lactulose dosing > 20 – 30 mg q2hrs
• Other considerations:
  • Avoid Fleet enemas (sodium-phosphate) in CKD and geriatric > populations
  • “The hand that writes for opioids also writes a bowel regimen”
    • Generally, start with scheduled MiraLAX (PEG) 17g daily + senna nightly
    • If severe and unrelieved by escalating therapies, can try methylnaltrexone
  • Lactulose can cause severe bloating and cramping
  • In patients unable to take PO: place DHT to deliver meds or rectal lactulose (important for patients with cirrhosis with AMS/HE).
  • In patients with CF (at risk for distal intestinal obstruction syndrome): ensure have pancreatic enzymes ordered, managed more like constipation than true obstruction: PO/ NGT MiraLAX QID or Golytely.
  • Acute colonic pseudo-obstruction (Ogilvie's syndrome): >12cm cecal diameter = severe dilation, risk of perforation. Treated with neostigmine, 2mg IV over 3 to 5 minutes. Monitor for bradycardia, hypotension, and dysrhythmias (relative contraindications: recent MI, asthma, PUD, epilepsy). Decompression with colonoscopy used in some cases.
  • Consider pelvic floor dysfunction, pelvic floor PT may be helpful

Laxatives
Mechanism	Examples	Effects
Bulking-agent	Psyllium seed (Metamucil), methylcellulose (Citrucel)	Absorb water and increase fecal bulk
Osmotic Laxatives	Polyethylene glycol (PEG = MiraLAX and Golytely), lactulose, mag-citrate	Hyperosmotic substances, pull fluid into GI tract
Stimulant Laxative	Senna, Bisacodyl (Dulcolax)	Stimulates peristalsis
Stool Softener	Docusate (Colace)	Generally ineffective
Opioid antagonist	Methylnaltrexone (Reslistor)	Peripheral acting opioid antagonist, inhibits opioid-induced decreased gastrointestinal motility
cGMP Agonist	Linaclotide (Linzess), Plecanatide (Trulance)	Stimulates intestinal secretion of Cl-/HCO3-
Prostaglandin derivative	Lubiprostone (Amitiza)	Increases intestinal chloride-rich fluid secretion