Constipation

Constipation has been defined as < 3 bowel movements per week, but this is not a required criterion, and symptoms may include straining to defecate, the passage of hard stools, a sensation of incomplete evacuation, and/or the need for self-digitation to evacuate stool. Associated features include nausea, abdominal bloating, anorexia, and, in patients with fecal impaction, paradoxical diarrhea. Constipation is categorized as primary constipation (i.e., functional constipation) when no underlying medical cause or offending medication is identified. Primary constipation is further categorized as normal transit constipation (most common), slow transit constipation, and defecatory disorders (i.e., outlet obstruction, pelvic dyssynergia). Secondary constipation is due to an identified cause (e.g., metabolic disorders, neurological disorders, mechanical obstruction, medication use). Evaluation of constipation in adults begins with identifying red flag features for colorectal malignancy and signs of secondary constipation that may warrant specific diagnostic studies and/or immediate referral to a specialist. In the absence of such signs, a clinical diagnosis of primary constipation can be established based on the Rome IV criteria for primary constipation in adults. Empiric management for primary constipation begins with nonpharmacological measures (e.g., increased fiber and fluid intake, education on avoiding stool-withholding behaviors) and bulk-forming laxatives. If symptoms persist, osmotic laxatives are recommended, followed by stimulant laxatives or intestinal secretagogues if necessary. Refractory symptoms after an appropriate trial of empiric therapy should prompt referral to gastroenterology to evaluate for disorders of defecation or colon transit. Secondary constipation is managed by treating the identified cause.

Constipation in infants, children, and adolescents is detailed separately.

• Prevalence
  • ∼ 14% of the general population experiences chronic constipation. ^[1]
  • Accounts for 3–5% of pediatric outpatient visits ^[2]
• Sex: ♀ > ♂ (3:1) ^[3]

Epidemiological data refers to the US, unless otherwise specified.

Constipation can be chronic or acute. Chronic constipation is typically classified as primary or secondary depending on the etiology. Acute constipation may be caused by lifestyle changes , hospitalization, immobility, or the acute onset of secondary causes of constipation. ^[4]

Primary constipation (functional constipation) ^[5][6][7]

Constipation with no identifiable secondary cause

Subtypes

• Normal transit constipation (most common): symptoms of constipation despite normal colonic transit time
• Defecatory disorders (also known as outlet obstruction or pelvic floor dyssynergia): difficulty evacuating stool once it reaches the rectum
  • Can manifest with prolonged straining, rectal discomfort, and trouble passing even soft stools
  • May be caused by inadequate rectal propulsion, increased resistance to evacuation , or other factors
• Slow transit constipation (least common): constipation with slow colonic transit time ^[8]

Risk factors for primary constipation ^[6]

• Lifestyle: poor diet, insufficient physical activity, obesity
• Genetic predisposition
• Psychological and behavioral disorders
• Alterations in normal gut flora, colonic dysmotility ^[5]

A predominance of abdominal bloating, cramping, and pain associated with constipation should increase the suspicion for IBS-C. ^[9]

Secondary constipation ^[5][6][7]

Constipation due to a medical disorder or medication

Both primary and secondary constipation can cause changes in stool consistency and defecation habits.

• Mechanism of altered stool consistency
  • External factors such as lack of exercise or inadequate fluid and fiber intake (primary constipation)/internal factors such as changes within the colon or rectum (secondary constipation) → slow passage of stool → prolonged absorption of water by the bowel → dry, hard stool → painful defecation → sensation of incomplete and irregular bowel emptying → constipation
• Mechanism of altered bowel motility
  • Effective peristalsis of the bowel is controlled by intrinsic (e.g., myenteric plexus) and extrinsic (e.g., sympathetic and parasympathetic) innervation.
  • Any alteration in bowel innervation may lead to ineffective peristalsis.
    • Drugs (e.g., calcium channel blockers, opiates, antispasmodics, antidepressants) ^[10] → altered autonomic outflow and bowel muscle contraction ^[11]
    • Endocrine pathology (e.g., hypothyroidism) → downregulated bowel motility
    • Neurological pathology (e.g., spinal injury, enteric neuropathy) → disease or trauma of bowel innervation
  • Ineffective peristalsis → difficult passage of stool regardless of stool consistency → sensation of incomplete and irregular bowel emptying

References:^[11][12]

• Manage complications
  • Identify and treat fecal impaction.
  • Suspected acute complication (e.g., bowel obstruction, bowel perforation) ^[14]
    • Urgent general surgery and/or gastroenterology consult
    • Obtain urgent abdominal imaging (CT or x-ray abdomen).
• Perform a clinical evaluation for constipation, including identification of:
  • Red flags in adults with constipation
  • Rome IV diagnostic criteria for primary constipation in adults
  • Risk factors for primary constipation
  • Clinical features or history (including medication history) suggestive of a secondary cause of constipation
• No abnormal findings, no red flags
  • Obtain a CBC to evaluate for anemia; other laboratory tests and imaging are not routinely recommended. ^[5][6][15]
  • Diagnose functional constipation if Rome IV diagnostic criteria for primary constipation in adults are met.
  • Initiate treatment.
• Abnormal findings or red flags
  • Red flags in constipation: Refer to gastroenterology for colonoscopy to evaluate for colorectal malignancy. ^[7]
  • Suspected secondary constipation: Identify and treat the underlying cause.
    • Obtain laboratory studies as needed.
    • Discontinue constipation-inducing medications when possible.
  • Suspected defecatory disorder: Refer to gastroenterology or urogynecology for anorectal function testing.

Acute-onset constipation associated with abdominal pain should raise suspicion for possible bowel obstruction. Complete bowel obstruction is a medical emergency.

A comprehensive history, physical examination, and assessment of red flag features should be conducted in all patients.

Red flags in constipation ^{[6][14][15][16]}

These features in a patient with constipation should prompt evaluation, e.g., with a diagnostic colonoscopy, for an underlying colorectal malignancy.

• Blood in stool
• Rectal bleeding
• Rectal tenesmus
• Clinically significant unintentional weight loss
• Unexplained iron deficiency anemia
• Jaundice
• Obstructive symptoms
• Patients > 50 years of age without previous screening for colorectal cancer; recent guidelines suggest 45 years as the cut-off to start screening ^{[4][6][13][17]}
• Abdominal or rectal mass
• Sudden change in bowel habits (e.g., onset of constipation without clear cause, change in stool caliber)
• Family history; of pertinent GI conditions (e.g., colorectal carcinoma, IBD)

A change in bowel habits (e.g., pencil-thin stool caliber) and/or rectal bleeding, especially in patients > 50 years of age, may indicate colorectal cancer and must be evaluated. ^[6]

Rome IV diagnostic criteria (adults) ^[9]

The Rome IV diagnostic criteria for primary constipation in adults are only applied if there is no suspected or identified cause of secondary constipation. All criteria must be present to establish a diagnosis. ^[7]

• Symptom onset ≥ 6 months prior
• The presence of ≥ 2 of the following symptoms in at least 25% of bowel movements over the last 3 months:
  • Passage of spontaneous stool < 3 times/week
  • Passage of hard or lumpy stool
  • Sensation of anorectal obstruction
  • Sensation of incomplete evacuation (rectal tenesmus)
  • Straining during attempts to defecate
  • Manual aid to evacuate stool
• Loose stools are rarely present except when laxatives are used.
• Rome IV criteria for irritable bowel syndrome are not met

Infrequent, hard stools (e.g., Bristol stool types 1 and 2) may suggest slow transit constipation. Straining and a sensation of incomplete evacuation may suggest a defecatory disorder. ^[9][14]

Physical examination ^[6][7][9]

A thorough physical examination should be performed, including the following:

• Abdominal examination to assess for GI pathology
• Inspection of perineum and anus
  • Evaluate for anal fissures and hemorrhoids.
  • Test the anal wink reflex: An absent anal wink reflex suggests a neurological pathology (e.g., sacral nerve injury). ^[18]
• Digital rectal examination
  • Check for masses (e.g., rectal carcinoma, fecal impaction, rectocele).
  • Assess anal sphincter tone and function for signs of pelvic floor dyssynergia. ^[4][19]

Diagnostics are not routinely required for primary constipation (i.e., if the Rome IV criteria for primary constipation in adults are met).

Laboratory studies ^[4][5][13]

Consider the following to evaluate for secondary causes of constipation as clinically indicated.

• CBC
• BMP
• Blood glucose levels, HbA1c
• Thyroid function tests
• Serum PTH levels and ionized calcium
• Serum magnesium

Colonoscopy ^[4][13][14]

• Indications
  • Red flags in constipation
  • Age > 50 years if age-appropriate colorectal cancer screening has not been performed; recent guidelines suggest starting screening at 45 years of age ^[4][13][17]
• Findings ^[16][20]
  • May be normal; colonoscopy has a low diagnostic yield for isolated constipation
  • May detect features of an underlying etiology: e.g., colorectal cancer, features of IBD, colonic stricture

In the absence of red flags in constipation, it is unlikely that colonoscopy will detect an underlying etiology. ^[16][20]

Imaging

• Indications: suspected complications
• Modalities: CT abdomen and pelvis with IV contrast, x-ray abdomen, POCUS ^[21][22]
• Findings
  • Uncomplicated constipation: may be normal; fecal loading with/without colonic dilation may be seen ^[14]
  • Features of complications: e.g., pneumoperitoenum , radiological signs of mechanical bowel obstruction

Advanced studies ^{[4][7][13][14]}

Patients with chronic primary constipation refractory to lifestyle modifications and empiric therapy should be referred to a specialist for additional workup, to identify the subtype and tailor management.

• Anorectal function testing: to evaluate for defecatory disorders
  • Balloon expulsion test
  • Anorectal manometry
  • Defecography (barium or MRI)
• Colon transit studies: to differentiate between normal transit constipation and slow transit constipation
  • Radiopaque marker study ^[4]
  • Wireless motility capsule study ^[4]

Approach ^[4][6][7][9]

This section details the management of patients with acute constipation (with no red flag features) and chronic primary constipation.

• First-line: nonpharmacological measures (e.g., high-fiber diet, increased fluid intake, and exercise) and/or trial of bulk-forming laxatives ^[5]
• Second-line: step-wise pharmacotherapy with laxatives from other classes
  • Begin with an osmotic laxative. ^[6][14][23]
  • If symptoms persist, add a short course of a stimulant laxative. ^[6][14]
• Constipation refractory to initial pharmacological treatment after ∼ 4 weeks ^[5]
  • Patients using opioids ^[24][25]
    • Initiate a peripherally acting μ-opioid receptor antagonist
    • See “Opioid-induced constipation” for details.
  • Patients not using opioids: Refer to gastroenterology for further evaluation and management. ^[5][6][7]

Nonpharmacological management of constipation ^[4][6][7][9]

• High-fiber diet: Recommend 20–35 g of dietary fiber daily, from high fiber-containing foods and/or bulk-forming laxatives (e.g., psyllium). ^[24]
• Hydration: Encourage recommended daily fluid intake. ^[26]
• Physical activity: Encourage regular physical exercise. ^[5][27]
• Healthy bowel habits
  • Schedule toileting for 10–15 minutes in the morning and ∼ 30 minutes after each meal to coincide with the gastrocolic reflex.
  • Use a step stool while on the toilet to raise the legs and straighten the colon.
  • Recognize and respond to urges to defecate. ^[28]
• Biofeedback: Recommend in patients with defecatory disorders who are able to actively participate. ^[13]

Introduce fiber slowly (over several weeks) and ensure adequate fluid intake simultaneously to prevent cramping and bloating. ^[24]

Constipation that worsens with fiber supplementation may suggest slow transit constipation or a defecatory disorder. ^[29]

Laxatives ^[4][5][15]

Important considerations

• Patients taking bulk-forming laxatives and osmotic laxatives should be instructed to ensure adequate water consumption.
• Chronic; osmotic or stimulant laxative use may lead to hypokalemia (which can further reduce bowel motility) and metabolic alkalosis. ^[30]
• Stimulant laxatives should be:
  • Prescribed for short-term use only; chronic stimulant laxative use may lead to dependency. ^[14][26]
  • Taken approximately 30 minutes after meals to coincide with the gastrocolic reflex ^[13]
• Stool softeners (e.g., docusate) should not be used for initial pharmacological treatment because their benefit has not been proven. ^[31]

Avoid bulk-forming laxatives if fecal impaction is suspected. ^[24]

Polyethylene glycol and lactulose are preferred osmotic laxatives. Bisacodyl and sodium picosulfate are preferred stimulant laxatives. ^[9][32]

Avoid the use of magnesium salts in patients with renal failure (magnesium is renally excreted) or cardiac dysfunction because of the risks of magnesium toxicity, other electrolyte abnormalities, and fluid shifts that could lead to volume overload. ^[24][34]

Intestinal secretagogues ^[4][14]

A group of drugs that improve colonic transit time by increasing intestinal secretion of water, bicarbonate, and chloride. These may be used to manage constipation refractory to other therapies.

• Agents
  • Linaclotide ^[5]
    • A peptide agonist of guanylate cyclase-C
    • Increases intestinal secretion of bicarbonate, chloride, and fluid, which improves fecal transit
  • Lubiprostone ^[5]
    • A prostaglandin derivative that activates chloride channels on the apical surfaces of enterocytes
    • Increases intestinal fluid secretion and improves fecal transit
• Adverse effects
  • Diarrhea
  • Nausea (lubiprostone)

Intestinal secretagogues are contraindicated in pregnancy.

Constipation in infants, children, and adolescents is detailed separately.

Constipation in older adults ^[7][24][28]

Epidemiology

• Constipation is common in older adults.
• Peak prevalence: 8–40% of individuals > 70 years of age ^[35]
• More common in older adults living in institutions (e.g., long-term health care facilities) than those living independently ^[6]

Etiology

• Primary constipation, related to risk factors that include:
  • Cognitive impairment
  • Prolonged immobility (e.g., patients who are bedridden and/or in a long-term care facility)
  • Stressors, social isolation ^[15]
  • Impaired urge to defecate
• Secondary constipation, due to, e.g.:
  • Colorectal malignancy
  • Polypharmacy (see “Constipation-inducing medications”)
  • Autonomic neuropathies, e.g., diabetes, Parkinson disease

Diagnostics

Similar to the approach to constipation in adults, with some special considerations

• Assess for fecal impaction. ^[7]
• Consider obtaining a BMP in patients with polypharmacy.

Fecal impaction is common in older adults and can manifest atypically with paradoxical diarrhea (due to decreased rectal sensation) and nonspecific symptoms (e.g., functional decline, delirium) ^[7]

Treatment ^[24][28]

• Manage fecal impaction if present.
• Lifestyle modifications: similar to management in all adults (see “Nonpharmacological management of constipation” above), with some special considerations
  • Fiber supplementation: Older adults are more likely to need fiber supplements to reach their daily fiber goals.
  • Fluid intake
    • Consider fluid-sensitive comorbidities (e.g., CHF, CKD), which are more common in older adults.
    • Assess and optimize the patient's ability to communicate and/or access their fluid needs.
  • Bowel habits: Discourage defecation in bedpans.
  • Physical activity: Increased exercise does not decrease constipation in older patients diagnosed with constipation. ^[24]
• Laxatives ^[24]
  • Required in most older adults with chronic constipation
  • Therapy should be individualized; see “Overview of laxatives” for dosages.
    • Preferred first-line agent: polyethylene glycol ^[24]
    • Persistent constipation: Consider a short course of stimulant laxatives.
    • Constipation refractory to the above measures: Refer to gastroenterology; consider intestinal secretagogues.
  • Magnesium salts: Use with caution and avoid long-term use. ^[24]
• Enemas ^[24]
  • Consider in patients who cannot tolerate oral laxatives or those with fecal impaction.
  • Enemas with mineral oil or plain warm water (without soap) are preferable. ^[28]
  • Avoid phosphate enemas because of adverse effects and toxicity. ^[9][28]
  • Consider glycerin suppositories as an alternative to enemas. ^[24]

Polyethylene glycol is preferred over lactulose and sorbitol because of the lower risk of electrolyte imbalances. ^[24]

Older patients are susceptible to severe laxative-associated adverse events, e.g., dehydration, electrolyte abnormalities, and hepatotoxicity. ^[28]

Clinical features

• Inability to defecate for days or weeks
• Normal bowel sounds
• Distended, tympanitic abdomen
• DRE: hard, impacted stools distending the rectum
• Tenesmus

Fecal impaction may manifest with diarrhea (paradoxical diarrhea) because of overflow fecal incontinence. ^[7]

Diagnostics

• Clinical diagnosis
• Abdominal x-ray (to rule out bowel perforation)
  • Findings:
    • Dilated bowel loops
    • Fecal shadows in the colon and rectum
    • Air-fluid levels may be visible.

Treatment ^[24][36]

• Rule out bowel perforation.
• Manual disimpaction ^[37]
  • Insert lubricated gloved index finger into the rectum.
  • Manually break up stool using a scissoring motion.
  • Gently extract fragments using circular motions with the finger bent.
  • Repeat as needed until the rectum is clear of fecalomas.
  • Consider procedural sedation and/or endoscopic disimpaction in severe cases.
• Administer osmotic enema (e.g., warm water enema or mineral oil enema).
• Consider the addition of stimulatory suppositories
  • Bisacodyl suppository
  • Glycerin suppository
• Prevention of recurrence
  • Start maintenance bowel regimen with osmotic laxative (e.g., polyethylene glycol or lactulose ).
  • Stop contributing medications.
  • Lifestyle modifications
  • See “Treatment.”
• For severe cases, consult surgery.

Clinical features

• Recent initiation of an opioid or dose adjustment
• New or worsening constipation
• Fecal impaction may be present
• Physical examination typically normal

Diagnostics ^[9]

• Clinical diagnosis
• Rome IV diagnostic criteria for OIC
  • Recent initiation of opioid treatment or a dose increase
  • AND ≥ 2 of the characteristic clinical features of functional constipation:
    • Passage of spontaneous bowel movement < 3 times/week
    • Passage of hard or lumpy stool (more than 25% of defecations)
    • Sensation of anorectal obstruction/blockage (more than 25% of defecations)
    • Manual aid to evacuate stool necessary (more than 25% of defecations)
    • Straining during attempts to defecate (more than 25% of defecations)
    • Sensation of incomplete evacuation (more than 25% of defecations)
  • Loose stools are rarely present without the use of laxatives
• Consider x-ray of the abdomen to rule out fecal impaction

Treatment ^[9][25]

• Similar to the treatment of primary constipation; see “Treatment.”
• Identify and treat any underlying organic cause.
• Lifestyle and dietary modification
• Evaluate the need for opiate therapy and discontinue/reduce dose if appropriate.
• Medical therapy
  • Laxative therapy
    • Osmotic laxative (e.g., polyethylene glycol or lactulose )
    • and/or stimulant laxative (e.g., senna )
  • Options for laxative-refractory OIC:
    • Peripherally acting μ-opioid receptor antagonists
      • Methylnaltrexone
      • Naldemedine
      • Naloxegol
    • Lubiprostone

Discontinue any additional laxatives when initiating a peripherally acting μ-opioid receptor antagonist.

• Fecal incontinence
• Fecal impaction, which may lead to bowel obstruction, or rarely, bowel perforation
• Anal fissures
• Hemorrhoids
• Megacolon
• Urinary retention
• Pelvic floor damage in women
• Rectal prolapse

References:^[3]

We list the most important complications. The selection is not exhaustive.