why does ulcerative colitis cause constipation?

Why Does Ulcerative Colitis Cause Constipation?

Ulcerative colitis is a chronic inflammatory bowel disease (IBD) that mainly affects the large intestine (colon) and rectum. Many people associate ulcerative colitis with frequent diarrhea, urgency, and abdominal pain. However, constipation can also be a real and confusing symptom for some people with ulcerative colitis—especially during certain phases of the disease.

Understanding why ulcerative colitis can cause constipation can help you better recognize symptoms, communicate with your healthcare provider, and make informed decisions about your care.

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A Quick Overview of Ulcerative Colitis

Ulcerative colitis causes ongoing inflammation and irritation of the inner lining of the colon. Over time, this inflammation can:

• Change how the colon moves stool
• Affect nerve signaling in the gut
• Alter fluid absorption
• Lead to structural changes in the bowel

While diarrhea is common during active inflammation, constipation can occur due to how ulcerative colitis disrupts normal bowel function.

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How the Colon Normally Works

In a healthy digestive system:

• The colon absorbs water from stool
• Muscles contract in a coordinated way to move stool forward
• Nerves help regulate timing and strength of these contractions

Ulcerative colitis interferes with all three of these processes, which helps explain why constipation can develop.

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Main Reasons Ulcerative Colitis Can Cause Constipation

1. Inflammation Slows Bowel Movement

Inflammation in ulcerative colitis can make the colon less effective at pushing stool forward.

• Swollen tissue may narrow the intestinal space
• Muscle contractions can become uncoordinated
• Stool may remain in the colon longer than usual

When stool stays in the colon too long, more water is absorbed, making it harder, drier, and more difficult to pass.

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2. Inflammation Limited to the Rectum (Proctitis)

Some people with ulcerative colitis have disease limited to the rectum, known as ulcerative proctitis.

In this situation:

• The rest of the colon may still absorb water normally
• Stool becomes firm before reaching the rectum
• The inflamed rectum may resist emptying

This can lead to constipation, straining, or a constant feeling of needing to go, even when little stool is present.

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3. Rectal Spasms and Pain Inhibit Bowel Movements

Inflammation in ulcerative colitis can irritate nerves in the rectum, leading to:

• Pain during bowel movements
• Muscle spasms
• Fear of passing stool due to discomfort

Over time, people may subconsciously delay bowel movements, which worsens constipation.

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4. Medications Used to Treat Ulcerative Colitis

Some medications commonly prescribed for ulcerative colitis can contribute to constipation, including:

• Antispasmodics (used to reduce cramping)
• Pain medications, especially those containing opioids
• Iron supplements, often prescribed for anemia
• Certain anti-diarrheal medications, if used when inflammation is still present

These medications are often necessary and helpful, but they can slow bowel movement as a side effect.

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5. Changes in Diet During Flares

During ulcerative colitis flares, many people change their diet to reduce symptoms. While this can be helpful, it may also lead to constipation.

Common contributing factors include:

• Reduced fiber intake
• Avoiding fruits, vegetables, or whole grains
• Drinking less water due to nausea or discomfort

Fiber and fluids help stool move smoothly. Without them, constipation becomes more likely.

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6. Dehydration

Ulcerative colitis can increase the risk of dehydration due to:

• Ongoing inflammation
• Reduced fluid intake
• Medication side effects

When the body is dehydrated, the colon pulls more water from stool, making it harder and more difficult to pass.

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7. Structural Changes in the Colon

Over time, chronic inflammation from ulcerative colitis can lead to physical changes, such as:

• Scarring of the colon wall
• Narrowing (strictures) in certain areas
• Reduced flexibility of bowel tissue

These changes can slow stool movement and contribute to constipation, particularly in long-standing disease.

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Constipation vs. “False Constipation” in Ulcerative Colitis

Some people with ulcerative colitis feel constipated even though stool is still present. This is sometimes called tenesmus.

Tenesmus may cause:

• A constant urge to have a bowel movement
• Passing small amounts of stool or mucus
• Feeling like the bowel never fully empties

This sensation comes from rectal inflammation rather than true stool buildup, but it can feel just as uncomfortable.

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When Constipation May Signal a Bigger Problem

While constipation can be part of ulcerative colitis, certain symptoms should not be ignored.

Speak to a doctor promptly if constipation is accompanied by:

• Severe or worsening abdominal pain
• Vomiting
• Unexplained weight loss
• Blood in the stool that is increasing
• Fever or signs of infection
• No bowel movement for several days with increasing discomfort

These symptoms may indicate complications that need medical attention.

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Understanding Your Symptoms Better

Ulcerative colitis symptoms can vary widely from person to person and can change over time. If you are unsure whether your constipation is related to ulcerative colitis or something else, you may find it helpful to do a free, online symptom check for Ulcerative Colitis to better understand possible causes and next steps.

This can be a useful starting point, but it does not replace professional medical care.

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Managing Constipation in Ulcerative Colitis

Management depends on the underlying cause. A doctor may recommend:

• Adjusting medications
• Treating active inflammation more effectively
• Carefully reintroducing fiber
• Improving hydration
• Using stool softeners or gentle laxatives when appropriate

Because ulcerative colitis affects everyone differently, self-treating constipation without guidance is not recommended.

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The Importance of Talking to a Doctor

Constipation in ulcerative colitis is not something you need to “just live with.” It can often be improved with the right approach. However, some causes can be serious if ignored.

Always speak to a doctor if:

• Constipation is new or worsening
• Symptoms interfere with daily life
• You notice bleeding, pain, or systemic symptoms
• You are unsure whether a symptom could be related to ulcerative colitis

A healthcare professional can help determine whether constipation is part of your ulcerative colitis, a medication side effect, or a sign of another condition that needs treatment.

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Key Takeaway

Ulcerative colitis can cause constipation due to inflammation, rectal involvement, nerve and muscle changes, medications, diet changes, dehydration, and long-term structural effects on the colon. While it may seem unexpected, constipation is a recognized and manageable symptom of ulcerative colitis. With proper evaluation and care, most people can find relief and reduce discomfort.

If you have concerns about symptoms that feel severe, unusual, or potentially life-threatening, speak to a doctor as soon as possible.