Constipation
Natalie Vellutini
Background
- Constipation is a largely symptom-based diagnosis based on Rome IV criteria.
- Symptoms: lumpy/hard stools, bloating/distension, abdominal discomfort, straining, use of digital maneuvers to evacuate, sensation of incomplete evacuation, frequency <3 BM per week.
- Presence of diarrhea/stool leakage with long-standing history of prior constipation raises concern for encopresis around stool mass.
- Bristol Stool Chart can be used to characterize stool over time.
- Common etiologies:
- Primary: anorectal or pelvic floor dysfunction, slow transit, functional (normal transit).
- Secondary: medications (opioids, Zofran, iron, anticholinergics), metabolic/endocrine (hypothyroidism, hypokalemia, hypercalcemia), obstructive (colorectal cancer, strictures, adhesions), pregnancy, celiac disease, neurogenic (spinal cord injury, MS, Parkinson disease, diabetes, autonomic dysregulation), lifestyle factors (low fiber/fluid intake, reduced mobility).
Workup
- Labs: BMP + Mg to evaluate electrolytes, consider TSH if chronic.
- Imaging: No need for imaging unless concern for obstruction → KUB/ CT.
- Consider anatomical risk of obstruction (prior abdominal surgeries, oncology history or risk for GI/GU malignancies, history of IBD/Crohn’s).
- Digital rectal exam to exclude anorectal mass, fecal impaction, sphincter tone, and pelvic floor dysfunction.
- Alarm symptoms? Hematochezia, unexplained weight loss, IDA, acute onset, family history of colorectal cancer → GI eval (colonoscopy).
Management
- Treat underlying cause: Stop or minimize offending medications, correct electrolyte abnormalities, etc. “The hand that writes for opioids also writes a bowel regimen”.
- Optimize lifestyle factors: out of bed/walking hallways, increase fluid intake (minimum 1.5 L daily), gradual increase in fiber intake to 20-35 g/day, consider squat assist device.
- Ensure bowel obstruction is ruled out before starting laxatives.
- Common first line bowel regimen osmotic +/- stimulant laxative -- scheduled MiraLAX (PEG) 17g daily (can increase to BID) + senna tablet nightly (can increase up to 2 tablets BID).
- Next line can consider addition of another osmotic laxative (lactulose 20g once, Milk of Magnesia).
- Last line can add suppository (bisacodyl) and/or enema (tap water or SMOG).
- Patients with fecal impaction may require manual disimpaction followed by colon evacuation.
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, Milk of Magnesia | Hyperosmotic substances, pull fluid into GI tract |
| Stimulant Laxative | Senna, Bisacodyl (Dulcolax) | Stimulates peristalsis |
| Stool Softener | Docusate (Colace) | Generally ineffective in isolation |
| Opioid antagonist | Methylnaltrexone (Relistor) | Peripheral acting opioid antagonist, inhibits opioidinduced decreased gastrointestinal motility |
| cGMP Agonist (Refractory Constipation) | Linaclotide (Linzess), Plecanatide (Trulance) | Stimulates intestinal secretion of Cl-/HCO3- |
| Prostaglandin derivative (Refractory Constipation) | Lubiprostone (Amitiza) | Increases intestinal chloriderich fluid secretion |
Considerations
- Avoid fleet enemas (sodium-phosphate) and milk of magnesia in CKD.
- Avoid fleet enemas in geriatric population.
- In patients unable to take PO, place DHT to deliver meds or lactulose enema (important for patients with cirrhosis with AMS/HE).
- If there is high suspicion for defecatory dysfunction or failed resolution of symptoms after initial laxative regimen, refer to GI for consideration of anorectal manometry/balloon expulsion test, pelvic floor PT, and/or secretagogue therapy.
