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Constipation

Last updated: March 4, 2021

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Constipation is the infrequent passage of stool. It is generally defined as ≤ 3 bowel movements per week, which may be associated with straining to defecate, the passage of hard stools, tenesmus, or the need for self-digitation to evacuate stool. It may be primary or secondary. Types of primary constipation (i.e., no identifiable organic cause) include normal transit constipation (e.g., due to inadequate calorie, fiber, or water intake), slow transit constipation, and pelvic floor dyssynergia. Secondary constipation may be drug-induced (e.g., opioid-induced constipation) or due to metabolic disorders (e.g., hypothyroidism), neurological disorders (e.g., spinal cord lesion), or mechanical obstruction of the bowel (e.g., colon cancer). Any identifiable underlying cause should be managed accordingly. In the absence of organic disease, constipation may resolve with regular exercise, hydration, and fiber supplementation. Osmotic or secretory laxatives may be considered in patients with persisting constipation. Long-term use of laxatives may result in dependency and paradoxical constipation.

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

Epidemiological data refers to the US, unless otherwise specified.

  • By course: acute or chronic
  • By etiology
    • Primary constipation (functional constipation): constipation in the absence of an identifiable medical disorder
    • Secondary constipation: constipation due to a medical disorder or medication [4]

References:[2][3][4]

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:[3][5][6][7]

Constipation is a clinical diagnosis and laboratory tests and imaging are not routinely indicated. Indications for diagnostics include the presence of any red flags (see below) or a suspected secondary cause of constipation, such as hypothyroidism.

Patient history

  • Ask about dietary habits, medication use, mobility, stool character and frequency, problems with defecation, and anorectal pain.
  • Additionally in children: delayed passage of meconium (e.g., Hirschsprung disease), voluntary withholding of stool (e.g., squatting, crying, crossing ankles, hiding), fecal (overflow) incontinence

Rome IV diagnostic criteria for functional constipation in adults

At least two of the following must have occurred in ≥ 1/4 of defecations during the past 12 weeks with onset of symptoms ≥ 6 months ago:

  • Passage of stool < 3 times/week
  • Passage of hard or lumpy stool
  • Sensation of anorectal obstruction/blockage
  • Manual aid to evacuate stool
  • Straining during attempts to defecate
  • Sensation of incomplete evacuation

Physical examination

Additional investigations

In patients with no red flag features, laboratory tests and imaging are not routinely recommended.

Red flags in patients with constipation

Children

Adults

A change in stool caliber (i.e., pencil-thin stool) and/or rectal bleeding in any patient > 50 years of age must be further investigated, as these features may be signs of colorectal cancer!

Acute-onset constipation should raise suspicion for bowel obstruction!

References:[2][3][4][5][8][9][10]

History of present illness

  • Onset
  • Duration
  • Frequency of bowel movements
  • Urge to defecate
  • Straining during defecation
  • Feeling of incomplete evacuation (tenesmus)
  • Manual disimpaction or self-digitation
  • Character of stools

Associated symptoms

  • Gastrointestinal
  • Anorectal
    • Painful defecation
    • Prolapsing mass
  • General

Past medical history, social history, and family history

General

Cardiopulmonary

Abdominal

In patients with constipation, do not forget to examine the inguinal and pelvic region for an obstructed inguinal or femoral hernia!

Neurological examination

Skin

Extremities

The diagnostic workup should be guided by the pretest probability of the relevant diagnoses. The following list includes some commonly used diagnostic tools that may be helpful when diagnosing or ruling out possible etiologies in a patient with constipation.

Laboratory studies

Imaging

Advanced diagnostic testing

In patients with no red flag features, laboratory tests and imaging are not routinely recommended.

The differential diagnoses listed here are not exhaustive.

  • Identify and treat any underlying conditions (see differential diagnoses).
  • Approach in adults [12]
  • Approach in children [3][9]
    • Infants 2 weeks to 6 months of age, without alarming features
      • May only require reassurance
        • Passage of stool is particularly variable in breastfed infants.
        • Parents who formula feed their children should be properly instructed on correct formula preparation.
      • Reassess in 2–4 weeks. [9]
      • If constipation persists, consider drug therapy (best initial: polyethylene glycol).
    • Children ≥ 6 months of age without suspected organic disease
      • Prompt laxative therapy (best initial: polyethylene glycol)
      • In combination with age-appropriate fiber, fluid, and physical activity requirements
      • Toilet training, if applicable [13]
    • Maintenance therapy: laxative therapy (polyethylene glycol or lactulose) until constipation is resolved for at least 1 month (treatment should then be tapered gradually) [9]
    • Further investigation to exclude an underlying disorder is warranted if there is a poor response to the treatments mentioned above or if constipation affects a child < 2 weeks of age.

References:[3][9][13][14][15]

Laxatives
Class Agents Mechanism of action Adverse effects
Osmotic laxatives
  • Polyethylene glycol (PEG): very effective and well-tolerated (best initial treatment)
  • Glycerin
  • Magnesium hydroxide
  • Magnesium citrate
  • Lactulose
  • Sorbitol
Stimulant laxatives/secretory laxatives
  • Senna
  • Bisacodyl
Emollient stool softener
  • Docusate
  • Emulsification (i.e., integration of water and fat) of stool → softening of stool → easier passage through the intestinal tract
Bulk-forming laxatives
  • Methylcellulose: chemical compound derived from cellulose
  • Psyllium husks
  • 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
  • Bloating
  • Worsening constipation or ileus if the patient doesn't take enough water with doses


Chronic laxative use may lead to dependency and/or hypokalemia, which can further reduce bowel motility!

Patients taking osmotic laxatives should be instructed to increase their water consumption.

  • Rule out life-threatening causes (e.g., mechanical bowel obstruction, toxic megacolon).
  • Identify and treat the underlying cause.
  • Discontinue any contributing medications (if appropriate)
  • Encourage PO fluid intake (2–3 L/day).
  • Start high-fiber diet (20–35 g/day). [16]
  • Encourage the consumption of vegetables, fruits (especially prunes), legumes, oats, rye, nuts, and seeds.
  • Mobilize patient/encourage ambulation.
  • Schedule regular toileting.
  • Start laxative therapy.

References:[2]

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

Clinical features

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

Diagnostics

Treatment [17][18]

Clinical features

Diagnostics [19]

  • 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 [19][20]

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

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