Merck Manual

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Some Causes and Features of Constipation

Some Causes and Features of Constipation

Cause

Examples/Common Features*

Tests

Acute constipation†

Twisting of a loop of intestine (volvulus), hernia, adhesions, and fecal impaction

Usually vomiting, crampy abdominal pain, and a distended abdomen

Abdominal x-rays

Sometimes CT

Ileus (temporary absence of the contractile movements of the intestine)

Major acute illness, such as sepsis (a severe infection of the bloodstream)

Immediately after abdominal surgery

Recent head or spinal cord injury

Prolonged bed rest

Abdominal x-rays

Drugs

Drugs with anticholinergic effects, such as antihistamines, some antidepressants, antipsychotic drugs, drugs used to treat Parkinson disease, and drugs that reduce or stop muscle spasms in the digestive tract (antispasmodic drugs)

Drugs containing certain metals (iron, aluminum, calcium, barium, or bismuth)

Opioids

Calcium channel blockers

Usually constipation that begins shortly after starting a new drug

A doctor's examination to exclude other causes of constipation

Sometimes stopping the drug to see whether constipation resolves

Chronic constipation†

Often constipation that has recently developed, persists for weeks, and gradually worsens as the tumor grows

Sometimes blood in stool (blood may be visible or detected during a doctor's examination)

Colonoscopy with biopsy

Metabolic disorders

Diabetes mellitus, an underactive thyroid gland (hypothyroidism), high levels of calcium in the blood (hypercalcemia), kidney failure, or pregnancy

Blood tests

Central nervous system disorders (affecting the brain or spinal cord)

MRI and/or CT

Peripheral nervous system disorders (affecting nerves outside the brain and spinal cord)

A doctor’s examination

Sometimes x-rays after barium is inserted in the rectum (barium enema) and/or biopsy

Systemic disorders

Systemic sclerosis, amyloidosis, skin inflammation plus muscle inflammation and muscle degeneration (dermatomyositis), or weakness and stiff muscles (myotonic dystrophy)

A doctor’s examination

Sometimes biopsy and/or blood tests

Functional disorders

Inactive colon (colonic inertia), irritable bowel syndrome, functional constipation, or disordered defecation

Often a sense of a blockage in the anus and/or rectum, prolonged or difficult defecation, or excessive straining

A doctor’s examination

Sometimes sigmoidoscopy

Dietary factors

Low-fiber diet or chronic laxative abuse

A doctor’s examination

* Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present.

† There is some overlap between causes of acute and chronic constipation. In particular, drugs are common causes of both.

CT = computed tomography; MRI = magnetic resonance imaging.