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Gastroenterology
Primary Care
Emergency Medicine

Acute Constipation

High EvidenceUpdated: 2025-12-22

On This Page

Red Flags

  • Vomiting + distension + no flatus (obstruction)
  • Rectal bleeding + weight loss (malignancy)
  • New constipation age >50
  • Peritoneal signs
Overview

Acute Constipation

1. Clinical Overview

Summary

Constipation is <3 bowel movements/week. In ED: rule out bowel obstruction, fecal impaction, malignancy before giving laxatives. Treat with osmotic laxatives (PEG first-line). Prevent opioid-induced constipation with stool softener + stimulant.

Key Facts

  • Definition: Infrequent or difficult bowel movements (<3/week)
  • First-line: PEG (MiraLAX) osmotic laxative
  • Red flag: New constipation >50 years → colonoscopy
  • Common cause: Opioids → prevent with stool softener + stimulant
2. Epidemiology

Overview

Constipation is defined as infrequent or difficult bowel movements, typically <3 per week. Acute constipation in the ED requires ruling out serious causes such as bowel obstruction or fecal impaction before initiating laxative therapy. Most cases are functional and respond to simple interventions.

Classification

By Etiology:

TypeExamples
Functional (primary)Slow transit, pelvic floor dysfunction
SecondaryMedications (opioids), metabolic (hypothyroid), neurological (Parkinson's)
ObstructiveColorectal cancer, stricture, volvulus

Epidemiology

  • Prevalence: 15-20% of adults; higher in elderly
  • More common in women
  • Major risk in hospitalized patients: Opioids, immobility, poor diet

Etiology

Common Causes:

CategoryExamples
MedicationsOpioids, anticholinergics, calcium channel blockers, iron
Diet/LifestyleLow fiber, dehydration, immobility
MetabolicHypothyroidism, hypercalcemia, diabetes
NeurologicalParkinson's disease, spinal cord injury, MS
StructuralColorectal cancer, stricture, rectocele
FunctionalSlow transit, pelvic floor dyssynergia
3. Pathophysiology

Mechanism

Functional Constipation:

  • Slowed colonic transit
  • Increased water absorption → Hard stool
  • Pelvic floor dysfunction → Difficult evacuation

Obstructive Constipation:

  • Mechanical blockage prevents stool passage
  • Proximal dilation, vomiting, distension

Opioid-Induced:

  • μ-opioid receptors in gut wall
  • Decreased motility, increased transit time
  • Increased fluid absorption → Hard stool
4. Clinical Presentation

Symptoms

SymptomDescription
Infrequent stools<3/week
StrainingDifficulty passing stool
Hard stoolsLumpy or pellet-like
Sensation of incomplete evacuation
Abdominal bloating
Rectal painWith defecation

History

Key Questions:

Physical Examination

FindingSignificance
Abdominal distensionObstruction, fecal loading
TympanyGas-filled loops
High-pitched bowel soundsObstruction
Absent bowel soundsIleus
TendernessObstruction, diverticulitis
Peritoneal signsPerforation
Rectal exam: Hard stoolFecal impaction
Rectal exam: MassTumor
How long has this been going on?
Common presentation.
Last bowel movement?
Common presentation.
Blood in stool, weight loss?
Common presentation.
Vomiting, ability to pass flatus?
Common presentation.
Medications (opioids, anticholinergics)?
Common presentation.
Diet, fluid intake, activity level?
Common presentation.
History of colon cancer or polyps?
Common presentation.
Prior abdominal surgeries (adhesions)?
Common presentation.
5. Clinical Examination

(Integrated into Clinical Presentation above)

Red Flags

Serious Causes to Exclude

FindingConcernAction
Vomiting + distension + no flatusBowel obstructionX-ray, surgery consult
Rectal bleeding + weight lossColorectal cancerRefer for colonoscopy
New constipation in age >0MalignancyColonoscopy referral
Fever + LLQ painDiverticulitisCT, antibiotics
Severe abdominal painObstruction, perforationImaging, surgery
Peritoneal signsPerforation, ischemiaCT, emergent surgery
6. Investigations

Differential Diagnosis

DiagnosisFeatures
Bowel obstructionComplete obstipation, vomiting, distension
IleusRecent surgery, medications, electrolyte disturbance
DiverticulitisLLQ pain, fever
Colorectal cancerWeight loss, rectal bleeding
Hirschsprung diseaseCongenital; pediatric
HypothyroidismFatigue, cold intolerance
Ogilvie syndromeMassive colonic dilation without obstruction
Diagnostic Approach

Clinical Diagnosis

  • Constipation is usually a clinical diagnosis
  • Imaging and labs for red flags or suspected obstruction

Imaging

Abdominal X-Ray:

FindingSignificance
Fecal loadingConfirms constipation
Dilated bowel loops + air-fluid levelsObstruction
Free airPerforation

CT Abdomen/Pelvis:

IndicationFindings
Suspected obstructionTransition point, distension
Suspected diverticulitisColonic wall thickening, stranding
Suspected malignancyMass

Laboratory Studies

TestIndication
CBCInfection, anemia (GI bleeding)
BMPElectrolytes, renal function (dehydration)
TSHHypothyroidism
CalciumHypercalcemia
7. Management

Principles

  1. Rule out obstruction before laxatives
  2. Treat underlying cause if identified
  3. Lifestyle modifications: Fluids, fiber, activity
  4. Laxatives for symptomatic relief
  5. Disimpaction for fecal impaction

Laxative Therapy

First-Line: Osmotic Laxatives:

AgentDoseNotes
Polyethylene glycol (PEG/MiraLAX)17 g dailyWell-tolerated, effective
Lactulose15-30 mL dailyCan cause bloating
Magnesium citrate150-300 mLAvoid in renal failure

Second-Line: Stimulant Laxatives:

AgentDoseNotes
Bisacodyl5-10 mg PO or suppositoryFast-acting
Senna8.6-17.2 mg POEffective

Adjuncts:

AgentDoseNotes
Docusate (stool softener)100 mg BIDLimited efficacy alone
Glycerin suppository1 rectallyLubricates

Fecal Impaction

StepIntervention
1Digital disimpaction (with lubrication)
2Warm water or saline enema
3Oil retention enema (mineral oil)
4Osmotic laxative after disimpaction
5Consider milk and molasses enema if refractory

Opioid-Induced Constipation

InterventionDetails
PreventionStool softener + stimulant when starting opioids
TreatmentStimulant laxatives (senna), osmotic (PEG)
RefractoryMethylnaltrexone (SC), naloxegol (PO)—peripherally acting μ-opioid antagonists

Bowel Obstruction Management

InterventionDetails
NPOBowel rest
NG tubeDecompress if vomiting
IV fluidsResuscitation
Correct electrolytes
Surgical consultationFor complete obstruction or complications
8. Complications

Disposition

Discharge Criteria

  • No signs of obstruction
  • Able to tolerate oral intake
  • Bowel movement achieved or imminent
  • Laxative regimen provided
  • Follow-up for red flags (colonoscopy if indicated)

Admission Criteria

  • Bowel obstruction
  • Severe fecal impaction not cleared
  • Dehydration or electrolyte disturbance
  • Inability to tolerate oral intake
  • Signs of perforation or ischemia

Referral

IndicationReferral
New constipation >0 yearsColonoscopy
Rectal bleeding, weight lossGI/Colonoscopy
Chronic/Refractory constipationGastroenterology
11. Patient/Layperson Explanation

Condition Explanation

  • "Constipation means your bowel movements are infrequent or difficult."
  • "Most cases are due to diet, fluids, or medications."
  • "Laxatives and lifestyle changes usually help."

Home Care

  • Increase fiber intake (25-30 g/day)
  • Drink plenty of fluids (at least 6-8 glasses/day)
  • Regular physical activity
  • Take laxatives as directed
  • If on opioids, take stool softeners preventively

Warning Signs to Return

  • Vomiting or inability to pass gas
  • Severe abdominal pain
  • Blood in stool
  • Fever
  • No bowel movement despite laxatives
9. Prognosis & Outcomes

Special Populations

Elderly

  • High prevalence
  • Often multifactorial (medications, immobility, diet)
  • Higher risk of fecal impaction
  • Be cautious with magnesium-containing laxatives (renal function)

Opioid Users

  • Very common complication
  • Preventive regimen essential
  • Consider peripherally acting μ-opioid antagonists

Pregnancy

  • Common due to hormonal changes and iron supplements
  • PEG and lactulose are safe
  • Avoid stimulants if possible

Neurological Disorders

  • Parkinson's, spinal cord injury increase risk
  • May need chronic laxative regimen
  • Avoid magnesium in renal impairment
Quality Metrics

Performance Indicators

MetricTargetRationale
Red flag assessment documented100%Identify serious causes
Rectal exam for impaction>0%Diagnose impaction
X-ray before laxatives (if obstruction concern)100%Avoid laxatives in obstruction
Colonoscopy referral for new constipation >0100%Cancer screening

Documentation Requirements

  • Duration and severity
  • Red flag assessment
  • Rectal exam findings
  • Laxative regimen prescribed
  • Follow-up plan
10. Evidence & Guidelines

Key Clinical Pearls

Diagnostic Pearls

  • Rule out obstruction before laxatives: X-ray if concerned
  • Rectal exam is essential: Detect impaction, masses
  • New constipation in elderly = Cancer until proven otherwise
  • Overflow incontinence can mimic diarrhea: Check for impaction
  • Opioid-induced is common: Prevent with stool softener + stimulant
  • Consider hypothyroidism and hypercalcemia: Check labs if chronic

Treatment Pearls

  • PEG is first-line osmotic: Safe, effective, well-tolerated
  • Stimulants work fast: Bisacodyl, senna
  • Docusate alone is weak: Combine with stimulant
  • Disimpact before oral laxatives: If impacted
  • Prevent opioid-induced constipation: Don't wait for symptoms
  • Methylnaltrexone for refractory opioid-induced: Peripheral μ-antagonist

Disposition Pearls

  • Most can be discharged: With laxatives and education
  • Admit for obstruction: Surgical emergency potential
  • Colonoscopy for red flags: New onset >50, bleeding, weight loss
  • Follow-up essential: If not improving
12. References
  1. Bharucha AE, et al. American Gastroenterological Association Medical Position Statement on Constipation. Gastroenterology. 2013;144(1):211-217.
  2. Wald A. Constipation: Advances in Diagnosis and Treatment. JAMA. 2016;315(2):185-191.
  3. Basilisco G, et al. Chronic constipation: a critical review. Dig Liver Dis. 2013;45(11):886-893.
  4. Ford AC, et al. Efficacy of osmotic laxatives in chronic idiopathic constipation. Am J Gastroenterol. 2018;113(9):1356-1365.
  5. Camilleri M. Opioid-induced constipation: challenges and therapeutic opportunities. Am J Gastroenterol. 2011;106(5):835-842.
  6. ACG Clinical Guideline: Management of Benign Anorectal Disorders. Am J Gastroenterol. 2014.
  7. NICE Guideline. Constipation in adults: diagnosis and management. 2021.
  8. UpToDate. Management of chronic constipation in adults. 2024.

Last updated: 2025-12-22

At a Glance

EvidenceHigh
Last Updated2025-12-22

Red Flags

  • Vomiting + distension + no flatus (obstruction)
  • Rectal bleeding + weight loss (malignancy)
  • New constipation age &gt;50
  • Peritoneal signs

Guidelines

  • NICE Guidelines
  • BTS Guidelines
  • RCUK Guidelines