Constipation occurs when stool or waste material moves too slowly through the large intestine. Feces that stay in the bowel too long before elimination become hard and dry. This results in difficult, painful, and infrequent bowel movements. In most cases, constipation is harmless. It's not a disease, but it might be a symptom of a disease.
Many elderly people believe they are constipated when they're not; thinking that less than one bowel movement a day is abnormal. In fact, as little as twice a week is fine so long as you go when you feel the need. In contrast, infants may go anywhere from 5 times daily to every fifth day!
When food leaves the stomach, it's still a partly digested mush. Your body recuperates 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-fiber 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:
- bowel obstructions, such as a tumor or benign growth
- chronic kidney failure
- irritable bowel syndrome
- neurogenic disorders such as Parkinson's disease, multiple sclerosis, or spinal cord injury
- rectal or colon cancer
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 anesthetic affects the bowel muscles for a few days after surgery. Lead poisoning and swallowing indigestible objects are other rare causes.
All of the following medications can slow the passage of feces through the intestine, provoking acute constipation:
- anticonvulsants used for epilepsy
- heart medications such as calcium-channel blockers
- iron supplements
- pain medications such as codeine and morphine
- some cough and cold medications containing dextromethorphan*
- some antacids
Overuse 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, and this can lead to bowel distension and a condition called melanosis coli.
People who are bedridden can develop severe acute blockages called fecal impaction. These may have to be removed by your doctor.