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 many cases, constipation is harmless. It's not a disease, but it might be a symptom of a disease.
Many 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 3 or 4 days or even longer for some healthy babies that are exclusively breast-fed.
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 and harder it gets.
Obviously, the quantity also increases if you wait to go to the toilet. A large, hard stool can be painful and difficult to pass, which then makes people reluctant to go, thereby creating a vicious cycle. This pattern of chronic constipation is especially common in children. It often begins when they start school. Many young children avoid 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 be the cause, such as:
- bowel obstructions, such as a tumour or benign growth
- chronic kidney failure
- irritable bowel syndrome
- neurologic disorders such as Parkinson's disease, multiple sclerosis, or spinal cord injury
- rectal or colon cancer
Acute constipation starts suddenly and lasts for 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 anesthesia affects the bowel muscles for a few days after surgery. Lead poisoning and swallowing indigestible objects are other occasional causes.
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 (dark brown colour inside the bowel).
People who are bedridden can develop severe acute blockages called fecal impaction. The stools may have to be removed by their doctor.
Symptoms and Complications
Symptoms of constipation can include:
- a sensation that the bowels haven't completely emptied
- bloating of the abdomen, and possibly a "rumbling" noise
- infrequent bowel movements
- hard, dry stools that are difficult to pass
- loss of appetite
- pain or pressure in the belly
- some bleeding as a result of straining
Constipation can cause complications. Very large, hard stools can stretch the anus, tearing the skin. These anal fissures can be very painful. Occasionally, a really tough bowel movement causes rectal prolapse, in which a small section of intestinal lining pokes out of the anus and has to be pushed back in.
Chronic constipation increases the risk of diverticulitis. This is when small pockets called diverticula are formed by the chronic increased pressure inside the bowel wall muscle and eventually get blocked and infected. Hemorrhoids can also be caused by the chronic pushing of constipation.
Making the Diagnosis
If constipation is a problem, see your doctor. A physical exam will show whether there are hard stools in your intestine or any unusual masses in your stomach. This will include a digital rectal exam to check muscle tone.
Your doctor might do a sigmoidoscopy or colonoscopy. This involves using a lighted tube with a camera on the end to look into part or all of the large intestine. A barium enema allows abnormalities of the large intestine to be seen on an X-ray. These procedures require some preparation to empty the bowel so that it can be seen on X-ray.
Treatment and Prevention
Constipation can be treated medically, but lifestyle changes are often very important. The following practices can both treat and prevent constipation:
- Avoid medications with constipating effects.
- Do physical exercise to stimulate the movement of waste through your intestines.
- Drink at least 8 glasses of fluid each day - water is best.
- Eat a diet that's high in bulk and low in processed foods.
- Increase dietary fibre to about 25 g per day for women and 38 g per day for men by eating whole grains, especially flaxseed, fruits, and vegetables (these add bulk to stools, making them easier to pass).
- Schedule regular times for bowel movements to condition your body (after breakfast, for instance).
- Use prune juice, stewed prunes, or figs to soften hard stools (increase the amount slowly to reduce gas).
Medications are usually brought in if changing diet and habits don't work. Most laxatives should be used sparingly as needed.
- Bulk-forming laxatives add bulk to the stool, stimulating defecation.
- Others act by coating the feces with oil, preventing water from being absorbed by the intestine.
- Some laxatives are irritants or stimulants that cause the lining of the intestine to contract, helping to push out the stool.
- Some laxatives work by pulling water back into the colon to ease transit.
Enemas and stool softeners can be used to increase the amount of water in your stool, causing it to become soft. This is useful if you can't or shouldn't be straining. This happens if you have anal fissures or rectal prolapse.
Medications can also create dependence, so use them only as directed by your health care professional.
*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.