About Constipation: Causes

When food leaves the stomach, it's still a partly digested mush. Your body reabsorbs valuable fluid from it while it's moved down the colon (large intestine). This transforms it into normal feces. The longer it stays in the colon, the drier it gets. That makes it harder.

Obviously, the quantity also increases if you wait to go to the toilet. A large, hard stool can be painful and difficult to pass. This can make people, especially children, reluctant to go, creating a vicious cycle. It's the common pattern of chronic constipation in children. It often begins when they start school. Many young children avoid the school toilets and end up waiting too long.

Chronic constipation can last for months or years. It's usually caused by poor diet, by some other disease, or by regularly ignoring the urge to go to the toilet. Low-fibre diets and insufficient water intake are the leading causes of constipation.

While most otherwise healthy people will occasionally experience constipation, certain diseases or conditions can also cause it:

  • chronic kidney failure
  • rectal or colon cancer
  • irritable bowel syndrome
  • neurogenic disorders such as Parkinson's disease, multiple sclerosis, or spinal cord injury
  • bowel obstructions, such as a tumour or benign growth
  • hypothyroidism

Acute constipation starts suddenly and lasts a few days. It can be caused by a blockage, prolonged inactivity, medication, dehydration, or missing a bowel movement. Pregnant women can develop constipation when the womb presses on the intestine. Sometimes, general anaesthetic affects the bowel muscles for a few days after surgery. Lead poisoning and swallowing indigestible objects are other occasional causes.

All of the following drugs can slow the passage of feces through the intestine, provoking acute constipation:

  • antidepressants
  • narcotics such as codeine
  • some antacids
  • heart medications such as calcium-channel blockers
  • diuretics
  • iron supplements
  • anticonvulsants used for epilepsy

Over-use of laxatives eventually makes the bowels less sensitive to the need to eliminate feces, and can cause chronic constipation. The bowels become dependent on laxatives to work.

People who are bedridden can develop severe acute blockages called fecal impaction. These may have to be removed by a doctor.

Learn more about Gastrointestinal