Constipation is a problem with passing stool, generally defined as having fewer than three bowel movements a week or having difficulty passing stool. Its key features include hard, dry or lumpy stools, straining or pain when going to the toilet, and a feeling that not all the stool has passed. Constipation may last for a short time or a long time; when it is long-lasting it is called chronic constipation, generally defined as having two or more of these core symptoms for three months or longer.
Constipation is not a disease in itself but can be a symptom of another problem. It is very common, affecting around 16 in 100 adults overall and about 1 in 3 adults aged 60 and older.
For functional (primary) constipation, doctors use the Rome IV criteria, which require two or more of the following for the last three months, with onset at least six months earlier: straining, hard or lumpy stools, a sensation of incomplete emptying, a sensation of blockage, the need for manual maneuvers to pass stool, or fewer than three spontaneous bowel movements per week, in the absence of loose stools without laxatives and without meeting the criteria for irritable bowel syndrome.
The most common symptoms of constipation are:
- Fewer than three stools a week
- Hard, dry or lumpy stools
- Straining or pain when passing stools
- A feeling that not all stool has passed (incomplete evacuation)
- A feeling that the rectum is blocked
- The need to use a finger to help pass stool
- Bloating, stomachache or cramps
Types
Functional (primary) constipation is usually divided into three types:
- Normal-transit constipation — stool moves through the colon at a normal rate, but the person still finds it difficult to pass and feels constipated; this is the most common form
- Slow-transit constipation — stool moves through the colon more slowly than normal, with infrequent bowel movements and reduced urge
- Defecatory (pelvic floor) disorders — the muscles of the pelvic floor do not coordinate properly to expel stool, sometimes called outlet dysfunction
Constipation can also be secondary, meaning it is caused by an identifiable factor such as a medication, another medical condition, or a physical blockage.
Causes and Risk Factors
Constipation generally occurs when stool moves too slowly through the colon, so the body absorbs too much water and the stool becomes hard and difficult to pass. Common contributing factors include:
Lifestyle factors:
- Not eating enough fibre
- Not drinking enough fluids
- Lack of regular physical activity
- Ignoring the urge to have a bowel movement
- Changes in routine, such as travel, and stress
Medications, including opioid painkillers, some antidepressants, iron supplements, certain antacids, some blood pressure medicines and antihistamines.
Medical conditions, such as an underactive thyroid, diabetes, irritable bowel syndrome, neurological conditions like Parkinson’s disease and multiple sclerosis, pelvic floor dysfunction, and blockages in the colon or rectum. Pregnancy is also a common cause.
Risk factors include older age, being a woman (especially during and after pregnancy), low physical activity, a low-fibre diet, and mental health conditions such as depression.
Diagnosis
Diagnosis begins with a review of medical history, symptoms, medications, diet and bowel habits, followed by a physical examination that often includes a digital rectal examination. Tests are not always needed but may include:
- Blood and urine tests, to look for conditions such as an underactive thyroid, diabetes or anemia
- Stool tests, to check for signs of infection, inflammation or bleeding
- Colonoscopy or sigmoidoscopy, to look inside the colon, particularly when warning signs are present, allowing biopsy and removal of polyps
For persistent or difficult cases, specialised tests can characterise the type of constipation:
- Colonic transit study, which tracks how quickly material moves through the intestines
- Anorectal manometry and a balloon expulsion test, which assess how the anus and rectum hold and release stool
- Defecography, a specialised X-ray to check for outlet-dysfunction causes
Treatment and Management
Treatment usually starts with lifestyle changes, adding medication when needed.
Lifestyle Changes
- Increasing dietary fibre from fruit, vegetables, beans and whole grains, aiming for roughly 18 to 30 grams per day
- Drinking more fluids
- Regular physical activity, even walking
- Good toilet habits, such as not ignoring the urge and establishing a regular routine, often after a meal
Over-the-Counter and Laxative Options
- Bulk-forming agents (fibre supplements) such as psyllium and methylcellulose
- Osmotic laxatives such as polyethylene glycol (PEG), magnesium-based products and lactulose
- Stimulant laxatives such as bisacodyl and senna
- Stool softeners such as docusate
Laxatives should not be used continuously for more than about two weeks without medical advice, as overuse can worsen symptoms.
Prescription Medication
When over-the-counter treatments are not enough, doctors may prescribe:
- Secretagogues, which increase fluid in the intestine, such as linaclotide, lubiprostone and plecanatide
- A prokinetic agent, prucalopride, which speeds up bowel movement
Other Treatments
Biofeedback therapy is used to retrain the pelvic floor muscles in people with defecatory (outlet) dysfunction. Surgery is rarely needed and is reserved for structural problems such as a blockage, stricture, or rectal prolapse.
Complications
Untreated or long-standing constipation can lead to:
- Hemorrhoids
- Anal fissures (tears in the lining of the anus)
- Fecal impaction (hard stool that becomes stuck)
- Rectal prolapse
When to See a Doctor
See a doctor if constipation is accompanied by any of the following:
- Blood in the stool, black stools or bleeding from the rectum
- Unexplained weight loss
- A sudden or new change in bowel habits
- Symptoms lasting longer than three weeks
- Persistent abdominal pain or severe pain with bowel movements
A family history of colorectal cancer, anemia, or new-onset symptoms at an older age are additional reasons to seek evaluation, as these may prompt a colonoscopy to rule out other conditions.