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Gastrointestinal Complications (PDQ®): Supportive care - Health Professional Information [NCI] - Constipation

Etiology of Constipation

Common factors that contribute to the development of constipation in the general population include the following:

  • Diet.
  • Altered bowel habits.
  • Inadequate fluid intake.
  • Lack of exercise.

Constipation can be a presenting symptom of cancer, or it can occur later as a side effect of a growing tumor or treatment of the tumor. For patients with cancer, additional causative factors are the following:[1]

  • The tumor itself.
  • Cancer-related problems.
  • Effects of drug therapy for cancer or for cancer pain.
  • Other concurrent processes such as organ failure, decreased mobility, and depression.

Physiologic factors include the following:

  • Inadequate oral intake.
  • Dehydration.
  • Inadequate intake of dietary fiber.
  • Organ failure.

Any or all of these factors can occur because of the disease process, aging, debilitation, or treatment. (Refer to the Nausea, Vomiting, Constipation, and Bowel Obstruction in Advanced Cancer section in the PDQ summary on Nausea and Vomiting for more information.)

Causes of Constipation


  • Chemotherapy (e.g., any agent that can cause autonomic nervous system changes such as vinca alkaloids, oxaliplatins, taxanes, and thalidomide).*
  • Opioids or sedatives.
  • Anticholinergic preparations (e.g., gastrointestinal antispasmodics, antiparkinsonism agents, and antidepressants).
  • Phenothiazines.
  • Calcium- and aluminum-based antacids.
  • Diuretics.
  • Vitamin supplements (e.g., iron and calcium).
  • Tranquilizers and sleeping medications.
  • General anesthesia and pudendal blocks.


  • Inadequate fluid intake.*

Altered bowel habits

  • Repeatedly ignoring defecation reflex.
  • Excessive use of laxatives and/or enemas.

Prolonged immobility* and/or inadequate exercise

  • Spinal cord injury or compression, fractures, fatigue, weakness, or inactivity (including bedrest).
  • Intolerance with respiratory or cardiac problems.

Bowel disorders

  • Irritable colon, diverticulitis, or tumor.*

Neuromuscular disorders (disruption of innervation leads to atony of the bowel)

  • Neurological lesions (cerebral tumors).
  • Spinal cord injury or compression.*
  • Paraplegia.
  • Cerebrovascular accident with paresis.
  • Weak abdominal muscles.

Metabolic disorders

  • Hypothyroidism and lead poisoning.
  • Uremia.*
  • Dehydration.*
  • Hypercalcemia.*
  • Hypokalemia.
  • Hyponatremia.


  • Chronic illness.
  • Anorexia.
  • Immobility.
  • Antidepressants.

Inability to increase intra-abdominal pressure

  • Emphysema.
  • Any neuromuscular impairment of the diaphragm or abdominal muscles.
  • Massive abdominal hernias.

Atony of muscles

  • Malnutrition.
  • Cachexia, anemia, or carcinoma.*
  • Senility.

Environmental factors

  • Inability to get to the bathroom without assistance.
  • Unfamiliar or hurried environment.
  • Excess heat leading to dehydration.
  • Change in bathroom habits (e.g., use of a bedpan).
  • Lack of privacy.
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