What is the difference between IBS and colitis?

Quick Answers

IBS (irritable bowel syndrome) and colitis are both conditions that affect the digestive system, but they have some key differences:

  • IBS is a functional gastrointestinal disorder that causes abdominal pain, bloating, and changes in bowel habits but does not damage the intestines.
  • Colitis refers to inflammation of the inner lining of the colon and can be caused by certain medical conditions like Crohn’s disease or ulcerative colitis.
  • IBS symptoms come and go, while colitis symptoms are more constant.
  • IBS does not cause permanent damage to the GI tract, while colitis can lead to complications like ulcers, bleeding, or intestinal damage if not properly treated.
  • IBS treatment focuses on managing symptoms through diet, stress relief, and medications. Colitis treatment depends on the cause but may involve anti-inflammatory drugs, immunosuppressants, or surgery.

Defining IBS

Irritable bowel syndrome (IBS) is a common functional gastrointestinal (GI) disorder, estimated to affect 10-15% of adults. It is characterized by chronic abdominal pain and altered bowel habits in the absence of any structural or biochemical abnormalities that would explain the symptoms. Some key facts about IBS:

  • IBS can cause symptoms like abdominal cramping, bloating, gas, diarrhea, constipation, or alternating diarrhea and constipation.
  • The exact cause of IBS is unknown, but contributing factors may include gut-brain interaction problems, intestinal muscle contractions, inflammation, and sensitivity to pain.
  • Triggers for IBS symptoms include stress, certain foods, hormonal changes, and gut infections.
  • IBS is diagnosed based on symptoms after excluding other possible gastrointestinal conditions through testing.
  • Treatment focuses on relieving and managing symptoms through diet changes, stress management, exercise, medication, probiotics, or cognitive behavioral therapy.
  • IBS does not cause permanent damage to the GI tract or increase risk of colorectal cancer.

Overall, IBS is a functional disorder, meaning the GI tract appears normal but does not function properly. It is a chronic but generally mild condition that can be well-managed with lifestyle and dietary modifications.

Understanding Colitis

Colitis refers to inflammation in the inner lining of the colon, also called the large intestine. Several conditions can cause colitis, including:

  • Ulcerative colitis: A chronic inflammatory bowel disease that causes inflammation and ulcers in the colon. It is an autoimmune condition of unknown cause.
  • Crohn’s disease: Another type of inflammatory bowel disease that can affect any part of the GI tract including the colon.
  • Infectious colitis: Colitis caused by bacterial, viral, or parasitic infections. Common causes are Clostridium difficile, Salmonella, Shigella, and cytomegalovirus.
  • Ischemic colitis: Inflammation of the colon due to reduced blood flow.
  • Chemical colitis: Injury to the colon lining caused by contact with harsh chemicals.
  • Diversion colitis: Inflammation of a defunctionalized colon segment after a colostomy.

Common symptoms of the various types of colitis include:

  • Diarrhea
  • Abdominal pain and cramping
  • Rectal bleeding
  • Urgency to have a bowel movement
  • Inability to pass stool despite urgency (functional constipation)
  • Fatigue and fever (in some cases)

Colitis can be acute and short-lived or chronic with periodic flare-ups. It is considered a more serious condition than IBS because inflammation can damage the colon and lead to complications like:

  • Ulcers and bleeding
  • Strictures (narrowing of the colon)
  • Increased colon cancer risk
  • Perforation or holes in the colon
  • Toxic megacolon (dangerous dilation and paralysis of the colon)

Therefore, proper treatment of the underlying condition is important to resolve inflammation and prevent complications of colitis.

Key Differences Between IBS and Colitis

While IBS and colitis both affect the large intestine and can have overlapping symptoms, there are several key differences between these two conditions:

1. Inflammation

The hallmark of colitis is inflammation of the intestinal lining. This inflammation is not present in IBS. Tests like colonoscopy or biopsy allow doctors to check for signs of inflammation and help distinguish between IBS and colitis.

2. Cause

IBS is considered a functional GI disorder, meaning there is no identifiable structural or chemical cause. It is believed to arise from problems with gut-brain interaction and intestinal motility. In contrast, colitis is caused by specific conditions that produce inflammation like Crohn’s disease, infections, or reduced blood flow.

3. Duration of symptoms

IBS tends to involve intermittent symptoms that fluctuate in severity. People may go through periods of constipation, diarrhea, or pain that last for days or weeks, interspersed between symptom-free periods. Colitis symptoms are more persistent and constant.

4. Progression

IBS symptoms tend to follow a chronic, waxing and waning course over a person’s lifetime. It does not cause progressive damage to the intestines. However, colitis is a progressive disease in conditions like ulcerative colitis or Crohn’s. Over time, repeated bouts of inflammation can permanently damage the GI tract.

5. Treatment

Because no structural abnormalities exist with IBS, treatment is focused on controlling symptoms. Dietary changes, antispasmodics, laxatives, anti-diarrheals, antidepressants, and psychotherapy help manage IBS symptoms. For colitis, treatment is aimed at reducing underlying inflammation with medications like aminosalicylates, steroids, immunosuppressants, or biologics.

6. Complications

IBS does not cause any permanent damage to the colon or increase risk of colorectal cancer. However, colitis can lead to serious complications like colon ulcers, perforation, strictures, bleeding, and increased cancer risk if inflammation is not adequately controlled.

Diagnosing IBS vs Colitis

Since IBS and colitis share overlapping symptoms, diagnostic tests are needed to distinguish between the two conditions:

  • Medical history: The duration and pattern of symptoms provides clues. IBS tends to follow an intermittent course. Colitis causes more constant symptoms.
  • Physical exam: The abdomen is checked for tenderness, distension, or masses.
  • Blood tests: Markers of inflammation like C-reactive protein and fecal calprotectin are elevated with colitis but not IBS. Blood counts may reveal anemia from colon bleeding with colitis.
  • Stool tests: Fecal calprotectin or lactoferrin levels are increased with intestinal inflammation. Stool cultures can be done to check for infectious colitis.
  • Imaging tests: A CT scan or colonoscopy can visualize inflammation, ulcers, strictures or other abnormalities seen with colitis.
  • Biopsies: Microscopic examination of colon tissue samples can confirm colitis by the presence of inflammatory cells.

In many cases of chronic diarrhea or abdominal pain, IBS may be suspected first based on symptoms. If empiric treatment for IBS does not relieve symptoms, more invasive tests like colonoscopy and biopsy may be undertaken to check for colitis.

IBS vs Colitis Treatment

Because IBS and colitis arise from different mechanisms, their treatment approaches differ significantly:

IBS Treatment

  • Dietary changes – avoid trigger foods, follow low FODMAP diet
  • Fiber supplements to improve abnormal bowel habits
  • Antispasmodics to reduce intestinal cramping and pain
  • Medications for diarrhea (loperamide) or constipation (laxatives)
  • Antidepressants to help with pain signaling
  • Psychotherapy and stress management techniques
  • Probiotics to improve gut microbiome balance
  • OTC medications for symptomatic relief of cramps, gas, bloating

Colitis Treatment

  • Aminosalicylates (mesalamine) to reduce inflammation
  • Corticosteroids to control acute flares
  • Immunomodulators to maintain remission
  • Biologics that block inflammatory pathways
  • Antibiotics or antivirals for infectious colitis
  • IV fluids and electrolyte management
  • Surgery to remove affected portions of intestine
  • Low residue diet, vitamin/mineral supplementation

While IBS management focuses on symptom control, colitis therapy aims to treat the underlying inflammation and pathology in the colon lining.

Prognosis and Outcomes

IBS and colitis generally have very different outcomes and impacts on a person’s health:

  • IBS – tends to follow a chronic, relapsing and remitting course. Symptoms fluctuate in severity over time and must be managed, but IBS does not reduce life expectancy or increase mortality.
  • Ulcerative colitis – also a chronic, lifelong condition. However, some patients suffer frequent severe flares requiring hospitalization. It can progress to life-threatening complications and increases risk of colon cancer.
  • Crohn’s disease – follows a progressive course with exacerbations and complications. Over time, strictures and poor nutrient absorption can develop requiring surgery. It increases risk for small bowel cancer.
  • Infectious colitis – usually an acute illness that resolves with treatment of the underlying infection. But some pathogens may cause recurring bouts of colitis.

Overall, colitis has the potential to be much more serious than IBS in terms of complications, surgeries, cancer risk, and mortality if inflammation cannot be controlled. But outcomes depend widely on proper treatment and management.

Coping and Living with IBS or Colitis

Both IBS and colitis can negatively impact quality of life. The unpredictable, embarrassing, and painful symptoms can disrupt work, school, relationships, social activities, and mental health. Some tips for coping:

  • Follow recommended treatment plans and work closely with your healthcare team.
  • Keep a food/symptom journal to identify triggers.
  • Manage stress levels through relaxation techniques, counseling, or cognitive behavioral therapy.
  • Join a support group to connect with other patients.
  • Communicate openly with friends and family about how they can support you.
  • Maintain as normal a lifestyle as possible during symptom-free periods.
  • Be patient and compassionate with yourself during difficult times.

Living with a chronic bowel disorder can be challenging. But utilizing an appropriate treatment strategy, developing coping techniques, and having a good support system can help patients manage their symptoms and improve overall wellbeing.


IBS and colitis are both gastrointestinal conditions that can significantly impact quality of life with uncomfortable and disruptive symptoms. However, they have distinct differences in their underlying causes, risks, diagnostic workup, treatment approaches, and long-term consequences.

IBS arises from abnormal gut motility and brain-gut interactions, causing functional impairment but no permanent damage. Colitis describes inflammation stemming from a wide range of medical conditions that can lead to serious complications if uncontrolled. Being aware of the differences between these two disorders allows for prompt diagnosis and optimal management.

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