Functional Constipation

What makes constipation "functional"

Constipation is called functional when it is not caused by a blockage, medicine, metabolic disorder or neurological disease. It is a disorder of gut-brain interaction: the bowel looks normal but does not work as it should.

Rome IV criteria (adults)

Two or more of the following in more than a quarter of bowel movements:

• straining
• lumpy or hard stools (Bristol stool types 1 to 2)
• a sensation of incomplete emptying
• a sensation of blockage at the anus
• manual maneuvers needed to help pass stool
• fewer than 3 spontaneous bowel movements a week

Plus: loose stools are rare without laxatives, and criteria for irritable bowel syndrome are not met. Symptoms must be present for the last 3 months, starting at least 6 months before diagnosis.

Functional constipation vs IBS with constipation

Both share symptoms. In IBS-C, abdominal pain linked to bowel movements is the main feature. In functional constipation, pain is absent or not dominant. Many people move between the two diagnoses over time.

Types and causes

Contributing factors:

• low fiber and fluid intake
• inactivity
• ignoring the urge to go
• travel and routine changes
• pregnancy
• older age
• anxiety, depression and eating disorders

Secondary causes to exclude

Medicines (opioids, iron, calcium channel blockers, anticholinergics, some antidepressants), hypothyroidism, high calcium, diabetes, Parkinson's disease, spinal cord problems, colon cancer, strictures and, in children, Hirschsprung disease.

Functional constipation in children

It is the most common cause of constipation in children, often starting:

• during toilet training
• when starting school
• after a painful bowel movement, leading to stool withholding

Children cross their legs, stiffen or hide to avoid passing stool. Retained stool forms a large mass, and liquid stool can leak around it, causing soiling (encopresis) that is often mistaken for diarrhea.

Signs that need checking for Hirschsprung disease or other causes include constipation from birth, delayed passage of the first stool beyond 48 hours, poor growth, vomiting, a swollen belly, or abnormal back or leg findings.

Diagnosis

A doctor takes a history (stool frequency and form, straining, medicines, diet, red flags) and examines the abdomen and anus. A digital rectal exam checks for impaction, fissures, hemorrhoids and whether the pelvic floor relaxes when asked to push.

Tests are usually limited to:

• blood count, calcium, thyroid function and glucose if indicated
• colonoscopy for red flags or age-appropriate colon cancer screening
• for persistent cases: anorectal manometry and balloon expulsion test (for dyssynergia), and colonic transit study (radio-opaque markers or wireless motility capsule)

Treatment

Step 1: Lifestyle and fiber

• Fiber: aim for 25 to 35 g a day. Psyllium has the best evidence. Increase gradually to limit gas.
• Fluids: drink enough to keep urine pale; extra fluid matters most when taking fiber.
• Toilet routine: try 15 to 30 minutes after breakfast, when the gut is most active; don't rush.
• Position: feet on a footstool so knees are above hips, lean forward.
• Activity: regular exercise helps.
• Foods: prunes, kiwifruit and high-fiber cereals have supporting evidence.

Step 2: Laxatives

• Osmotic laxatives: polyethylene glycol (PEG 3350) is first-line in adults and children; lactulose and magnesium are alternatives (magnesium with caution in kidney disease).
• Stimulant laxatives: senna and bisacodyl, effective and safe for regular use when needed.
• Stool softeners (docusate) have little evidence.

Step 3: Prescription medicines

For persistent constipation, guidelines support linaclotide, plecanatide, lubiprostone and prucalopride.

Pelvic floor dysfunction

Biofeedback therapy with a pelvic floor physical therapist is the treatment of choice for dyssynergic defecation and helps most people. Laxatives alone often fail in this group.

Children

• Disimpaction with PEG at a higher dose for several days if there is a stool mass.
• Maintenance PEG daily for months, gradually tapered once regular soft stools are established.
• Behavioral approach: scheduled toilet sits after meals, rewards, a footstool, and avoiding punishment for accidents.
• Avoiding excessive milk intake in toddlers, and adequate fiber and fluids.

Complications

• hemorrhoids and anal fissures
• fecal impaction
• overflow soiling
• rectal prolapse
• reduced quality of life

Frequently asked questions

What is functional constipation?

It is chronic constipation without an underlying disease or structural cause. It is diagnosed when symptoms such as straining, hard stools, incomplete emptying or fewer than 3 bowel movements a week have been present for at least 3 months, using the Rome IV criteria.

What is the best treatment for functional constipation?

Start with fiber (especially psyllium), fluids and a regular toilet routine. If that is not enough, polyethylene glycol is the first-line laxative. Stimulant laxatives and prescription medicines help persistent cases, and biofeedback is best when the pelvic floor does not relax properly.

Is it safe to take laxatives every day?

For chronic constipation, daily polyethylene glycol is considered safe long term, and stimulant laxatives such as senna are also safe when used as needed or regularly under medical advice. Talk to a doctor if you need laxatives for more than a couple of weeks.

How long does functional constipation last in children?

With consistent treatment, many children improve within weeks, but treatment often needs to continue for 6 months or longer to prevent relapse. Stopping too early is a common reason constipation returns.