Constipation

Last updated: June 23, 2022

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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

Etiology of secondary constipation [5][6][7]
Gastrointestinal causes

Neurological causes

Metabolic causes
Connective tissue disorders

Constipation-inducing medications

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

References:[11][12]

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.

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:

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.

Colonoscopy [4][13][14]

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

Imaging

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.

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

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

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

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

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]

Overview of laxatives [4][5][15][28][33]
Class Agents Mechanism of action Adverse effects
Bulk-forming laxatives (fiber)
  • Methylcellulose : chemical compound derived from cellulose
  • Psyllium husks : outer coating of the seed of the Plantago ovata plant
  • Polycarbophil
  • Bulk-forming laxatives are indigestible, not systemically absorbed.
  • Soluble fibers increase water absorption in the intestinal lumen → stretching of the bowel wall → stimulation of peristalsis
Osmotic laxatives
  • Polyethylene glycol (PEG): very effective and well tolerated (best initial treatment) [5][24]
  • Disaccharides
  • Magnesium salts
    • Magnesium hydroxide [15]
    • Magnesium citrate [24]
  • Glycerin suppository
Stimulant laxatives (secretory laxatives)
  • Bisacodyl [5]
  • Sodium picosulfate [15]
  • Senna [5]
Emollient stool softener
  • Docusate (not recommended) [31]
  • Theoretically, emulsification (i.e., integration of water and fat) of stool → softening of stool → easier passage through the intestinal tract
  • Abdominal pain, cramping

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.

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

Diagnostics

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

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]
  • 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

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
  • Prevention of recurrence
  • For severe cases, consult surgery.

Clinical features

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]

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

References:[3]

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

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