Constipation

Constipation is discomfort associated with a reduced frequency of bowel movements and an increase in stool consistency (hard) that leads to difficulty in defecating. Constipation often presents with pain, bloating, flatulence and feelings of incomplete evacuation.  If left untreated it can lead to nausea and vomiting, overflow diarrhea, urinary dysfunction, tenesmus, anorexia, confusion, fecal impaction and bowel obstruction.   Approximately 50% of patients report constipation but about 80% of patients require laxatives.

CAUSES
The most common causes of constipation include:

  • pharmacologic: opioids*, phenothiazines, anticholinergic, antacids(aluminum, calcium), Tricyclic antidepressants, diuretics;
  • metabolic: hypothyroid, hypokalemia, hypercalcemia;
  • diet: low fiber intake;
  • motility: decreased motility;
  • ileus: acute illness (Ogilvie's syndrome), electrolyte abnormality, drugs;
  • mechanical obstruction: tumor, rectocoele, hernia, adhesions;
  • dehydration;
  • autonomic dysfunction: diabetes, renal failure, advanced cancer, drugs;
  • concurrent disorders: Hemorrhoids, anal fissure.

ASSESSMENT
History: It is important to start the assessment for constipation with a detailed history including information on:

  • the normal pattern of bowel movements;
  • frequency and consistency of stools;
  • nausea and vomiting;
  • pain;
  • distention and discomfort;
  • mobility and nutrition.

Physical Exam should be preformed including:

  • general observation;
  • abdominal palpation;
  • Rectal or stomal examination. 

Rectal exam is important to detect stool mass, fecal impaction (98% occurs in rectum), hypotonia from spinal cord invasion, tumor mass etc. 

In addition, information about access to the toilet or commode is important as issues such as limited mobility, privacy, and need for assistance may exacerbate constipation.  In some cases, when the diagnosis of constipation is difficult, an x-ray of the abdomen can be helpful.

MANAGEMENT

Non-Pharmacological Interventions
Encourage the following:

  • increased fluid intake if not in advanced stages of illness, last hours of life;
  • scheduled toileting: same time each day, after meals;
  • position: try to get onto commode or at least sitting up.

Avoid bulk agents like bran since 1) normalize stool but not a good laxative, 2) need to use with a lot of water, 3) tastes bad, 4) in debilitated patients may precipitate obstruction by forming a viscous mass.

Pharmacological Interventions

Laxatives

Stimulant laxatives

The aim of stimulant laxative therapy is to irritate the bowel and increase peristaltic activity by stimulating myenteric plexus. Their latency of action is typically 6-12 hours.  Stimulant laxative can result in colic and severe purgation.  The dose should be titrated and colic may be reduced by giving the daily requirement in divided doses.

Consider:
Prune juice
Senna
Bisacodyl

Osmotic laxatives
Osmotic laxatives draw water into the bowel lumen. They undergo bacterial degradation in the colon that decreases intestinal pH, stimulates peristalsis and increases bulk by stimulating bacterial growth. Stool moisture is increased, as is the overall stool volume.  Can result in bloating, colic, and flatulence.  Osmotic laxatives should always be accompanied with increased fluid intake.

Detergent laxatives (stool softeners)
Detergent laxatives facilitate the dissolution of fat in water and increase the water content of stool. Docusate also increases the secretion of water and sodium chloride in stool and may increase peristalsis.

Prokinetic agents
Prokinetic agents stimulate the bowel's myenteric plexus and increase peristaltic activity and stool movement.

Enemas

Lubricant stimulants
Lubricant stimulants are often given overnight and lubricate the stool and irritate the bowel, thus increasing peristaltic activity and stool movement. Use if impacted with hard feces to soften fecal mass. May need manual disimpaction or large volume enemas.

Consider:
Glycerine suppositories
Oils: mineral, peanut

Large-volume enemas
Large-volume enemas soften stool by increasing its water content. They also distend the colon and induce peristalsis.

Consider:
Warm water


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