Constipation

at the bedside

airway, breathing, circulation; full vitals; IV access if vomiting or unwell
why admitted, what changed → days since stool and flatus, pain, distension, vomiting; recent surgery or procedure; opioids started or increased
drug chart and MAR → which laxatives are prescribed, and were they actually given; opioids and anticholinergics on the chart
obstruction or ileus → judge the whole picture: pain, distension, vomiting, no flatus; bowel sounds are neither sensitive nor specific. not a laxative problem
rectal exam → hard stool in the vault is impaction; an empty vault does not exclude impaction higher up, and neither finding establishes or excludes obstruction

escalate now if

vomiting, distension, no flatus, or severe or colicky pain → obstruction: no laxative or enema, urgent surgical discussion
distension without colic after surgery or on opioids → ileus
new leg weakness, saddle numbness or retention → cauda equina → back pain
“diarrhea” in a frail or immobile patient after days without stool → impaction with overflow, antidiarrheals make it worse
peritonism, fever, blood, or pain out of proportion to the exam → perforation or ischemia → abdominal pain

mechanical obstruction → adhesions, hernia, tumor, volvulus; colicky pain, vomiting, no flatus
ileus → after surgery, opioids, electrolytes, sepsis; distension without colic, little pain
fecal impaction → elderly, immobile, opioids; overflow leakage, urinary retention
drugs → opioids, anticholinergics, calcium channel blockers, iron, ondansetron, antipsychotics, diuretics
metabolic → hypercalcemia, hypokalemia, hypothyroidism, dehydration → calcium, potassium
simple → immobility, low intake, no privacy, a bedpan; the usual ward cause

history → days since stool, flatus, pain (colicky or constant), distension, vomiting, recent surgery, usual bowel habit
drug chart → opioids (dose and duration), anticholinergics, iron, calcium channel blockers, ondansetron, antipsychotics
exam → distension, tenderness, peritonism, hernial orifices, scars, palpable bladder; rectal exam for stool and its consistency, blood, mass, tone

simple constipation needs no tests
RFT, calcium, magnesium, glucose → new, refractory or unexplained; TSH → if chronic and unexplained
abdominal X-ray → not to measure stool load, and a normal film does not exclude mechanical obstruction; at most a first look for dilated loops or free air while CT is arranged
CT abdomen and pelvis → the test when obstruction, ileus or perforation is suspected and imaging is needed; peritonism or suspected ischemia → bloods and imaging as for abdominal pain

ileus or obstruction suspected

no further laxative, suppository or enema until obstruction and perforation are excluded; hold what is already charted
NPO if vomiting or distended; IV fluids; correct K and Mg → potassium, magnesium; NG tube on free drainage if vomiting or distended, X-ray to confirm position
mechanical obstruction → urgent surgical discussion now; how fast is set by ischemia, perforation or strangulation: peritonism, fever, pain out of proportion, rising lactate, a hernia that will not reduce → immediate → abdominal pain
ileus → stop or reduce opioids and anticholinergics where possible, mobilize, correct electrolytes, treat sepsis; distension or vomiting that progresses → CT and surgical review

fecal impaction

stool in the vault → glycerin or bisacodyl suppository first; tap-water or mineral-oil enema if the suppository fails or the stool is hard
manual disimpaction only when the exam shows a hard rectal mass that rectal measures will not clear, the patient tolerates it, there is no contraindication (recent anorectal or pelvic surgery, neutropenia, bleeding risk) and local protocol allows; analgesia before, stop if pain or bleeding → pain
empty vault but impaction likely higher → oral osmotic at the doses below; no result by the next round → treating team or GI
then an osmotic laxative to prevent recurrence; look for overflow (no antidiarrheals) and a palpable bladder → urinary retention

phosphate enema → avoid in older adults, renal dysfunction, dehydration, heart failure, and whenever obstruction is possible: hyperphosphatemia, hypocalcemia, AKI, severe electrolyte disturbance; do not repeat a dose; tap-water or mineral-oil enema instead

simple constipation: laxatives

first → fix the ward causes: fluids, mobilize, commode not bedpan, privacy; check the MAR for what was actually given before adding anything
start or optimize one agent → osmotic: polyethylene glycol (Movicol) 1–2 sachets PO BD or lactulose 15–30 mL PO BD; or stimulant: senna 7.5–15 mg PO nocte or bisacodyl 5–10 mg PO nocte; not every patient needs both from the start
no stool by the next day → add the other class; rectum loaded → bisacodyl 10 mg PR or glycerin suppository
on opioids → prophylaxis: senna plus an osmotic laxative from the first opioid dose; reduce or rotate the opioid if possible; refractory on full-dose laxatives → naloxegol or methylnaltrexone by the treating team, contraindicated with known or suspected bowel obstruction
cramps → paracetamol 1 g PO/IV; no hyoscine butylbromide: anticholinergic, worsens constipation and ileus, wrong if obstruction is possible; colic that needs more is a reason to re-examine → abdominal pain

reassess

when → after any enema or disimpaction, and at the next round; sooner if pain, vomiting or distension change
what → stool passed and consistency on the chart, flatus, distension, pain, vomiting, vitals; bladder if impacted; electrolytes after a phosphate enema in anyone at risk
not working → laxatives escalated with no stool and new distension, vomiting or pain: stop escalating and go back to ileus or obstruction; impaction that rectal measures have not cleared → treating team or GI

hand over → obstruction excluded or still possible, what was given and when (MAR), stool chart, overflow or retention, review time

source	type
AGA/ACG 2023 chronic idiopathic constipation guideline	international guideline
AGA 2019 opioid-induced constipation guideline	international guideline
AGA 2013 medical position statement on constipation	specialty-society guidance
ACR Appropriateness Criteria, suspected small-bowel obstruction	specialty-society guidance

Verify indication, dose, allergies, interactions, renal/hepatic function and local protocols before prescribing.

free the on-call checklist covers the whole shift on one printable page.

studying for the IM exam? the IM Rapid Review covers this in the same format. see the sample chapter.

reviewed Jul 2026updated Oct 2026file complaint/constipation