constipation
Meaning of constipation: Straining and hard stool define it more than frequency does, because the normal range between healthy people is remarkably wide.
Definition of constipation
Constipation is difficulty passing stool: stools that are hard, small or painful to pass, a sense that the bowel has not emptied, or bowel movements coming less often than is usual for that person. It is judged against an individual pattern rather than a fixed number of movements per week, so the same frequency can be normal for one person and abnormal for another.
What slows the bowel down?
Stool moves by peristalsis, waves of muscle contraction pushing contents along, while the colon draws water back out of them. Anything that slows the wave, or leaves stool in contact with the colon for longer, produces a harder and drier result. Low fluid intake, little fiber and inactivity all act this way. Many medicines do too, opioid painkillers most strongly, along with iron tablets, some antidepressants and certain blood pressure drugs. Sluggish bowel activity also accompanies an underactive thyroid, diabetes, Parkinson disease, spinal injury, a low blood potassium and a high blood calcium. A separate group of people move stool through the colon normally but cannot coordinate the pelvic floor at the moment of emptying, so the stool arrives and does not leave.
How do the different laxatives work?
| Type | Mechanism | Example |
|---|---|---|
| Bulk forming | Holds water in the stool, adding volume | Psyllium husk |
| Osmotic | Draws water into the bowel | Macrogol, lactulose |
| Stimulant | Prompts the bowel wall to contract | Senna, bisacodyl |
| Softener or lubricant | Eases passage of the stool itself | Docusate, mineral oil |
The groups differ in speed and in what they need in order to work. A bulk forming laxative depends on adequate fluid and adds little without it, while an osmotic agent brings water with it. Stimulants act fastest and cause cramping most often.
When does it point to something else?
Constipation is a symptom, and for most people it reflects diet, fluid, activity or medication. Certain accompaniments place it in another category: blood in the stool, unintended weight loss, anemia from iron deficiency, a persistent change in the caliber of the stool, or a first appearance in later adult life with no obvious explanation. Those combinations raise the possibility of a narrowing in the colon, and a colonoscopy looks directly for one. Constipation alternating with looser stool over years, tied to abdominal pain, fits a functional bowel disorder instead. Complete inability to pass stool or wind, with a distended painful abdomen and vomiting, describes obstruction and is a different picture altogether.
Used in a sentence
Constipation developed soon after the opioid dose was increased.
Good to know
Constipation is a symptom rather than a diagnosis, and a persistent change in bowel habit in an adult, blood in the stool, anemia or unintended weight loss alongside it are findings that prompt examination of the colon.
Word origin
Where “constipation” comes from
From the Latin constipare, to press or crowd together, from con-, together, and stipare, to pack.