Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are two distinct gastrointestinal (GI) conditions. Despite having similar acronyms and some overlapping symptoms, the two conditions are very different in how they are diagnosed and treated. If you regularly struggle with digestive upset and abdominal pain, it's important to determine if you have IBS, IBD, or another GI condition to properly treat your symptoms and find relief. 

What is IBS?

Irritable bowel syndrome (IBS) is a common disorder characterized by abdominal pain or discomfort, bloating, gas, and altered bowel habits, such as recurrent diarrhea, constipation, or both. IBS is classified as a functional gastrointestinal disorder, which means there is some type of disturbance in bowel function.1 The term “irritable” is used because the nerve endings in the lining of the bowel are unusually sensitive, and the nerves that control the muscles of the gut are unusually active. 

Abdominal pain is a key symptom of IBS and is often relieved with the passing of a bowel movement. The signs and symptoms of IBS can range from mildly inconvenient to severely debilitating, adversely affecting a person's quality of life.1,2  

IBS is a chronic condition that requires long-term management. According to the International Foundation for Functional Gastrointestinal Disorders, IBS affects between 25 million and 45 million U.S. adults. It’s estimated that between 20 and 40 percent of visits to gastroenterologists are due to IBS symptoms and about two-thirds of IBS sufferers are female.3 

What Causes IBS?

The causes of IBS are not completely understood. Factors that appear to play a role include:4,5 

  1. Muscle contractions in the intestine. Individuals with IBS often have irregular small intestine and colon motility patterns, meaning the muscle contractions are not functioning the way they should. Contractions that are stronger and last longer than normal can cause gas, bloating, and diarrhea. Weak intestinal contractions can slow food passage and lead to constipation.
  2. The nervous system. Abnormalities in the nerves in the digestive system might cause an individual to experience greater than normal discomfort when the abdomen stretches from gas or stool. Poorly coordinated signals between the brain and the intestines can cause the body to overreact to changes that normally occur in the digestive process, resulting in pain, diarrhea, or constipation.
  3. A post infection state. IBS can develop after a bout of diarrhea (gastroenteritis) caused by bacteria or a virus. IBS might also be associated with a surplus of bacteria in the intestines – particularly types of bacteria not commonly found in that part of the digestive tract. 
  4. Early life stress. Individuals exposed to stressful events, especially in childhood, tend to have more symptoms of IBS.

Changes in gut microbes. The bacteria, fungi, and viruses that normally reside in the intestines play a key role in health. Research indicates that microbes in the gut of individuals with IBS can differ from those in healthy people. It's unclear, however, if this difference causes IBS, or if IBS leads to changes in the gut microbes. 

Common Triggers of IBS

The signs and symptoms of IBS can come and go over time and are often triggered by ordinary stimuli, including certain foods, stress, hormonal changes, and some medications.4,6 

  1. Food. True food allergies are extremely rare and seldomly cause IBS. But many people have worse IBS symptoms when they eat or drink certain foods or beverages, including wheat, dairy products, citrus fruits, beans, some sugars, cabbage, and carbonated drinks.
  2. Stress. Most people with IBS experience worse or more frequent signs and symptoms during periods of increased stress. 

Diagnosis and Treatment for IBS

There isn't a specific test that determines if you have IBS. Instead, the condition is diagnosed by your symptoms and by ruling out other possible health conditions. A doctor likely will take a detailed medical history, conduct a thorough physical exam, collect blood and stool samples, and, if necessary, perform additional diagnostic tests. If you are diagnosed with IBS, the condition will be classified by subtype: IBS with diarrhea, IBS with constipation, or IBS mixed (constipation and diarrhea).4,7

Treatment focuses on relieving specific symptoms to improve your quality of life. Some people can find relief with lifestyle changes like diet, exercise, and stress management techniques. More severe symptoms might require over-the-counter or prescription medications. In addition, counseling can be helpful – especially for people with depression or stress that makes symptoms worse.4,8 Some research indicates that acupuncture and gut-directed hypnotherapy also can reduce IBS symptoms.9 

What is IBD?

Inflammatory bowel disease (IBD) is chronic inflammation of the gastrointestinal tract. IBD is a disease that can damage the GI tract and increase the risk of other health conditions, including colon cancer – if the disease affects the colon.10,11 According to the Centers for Disease Control and Prevention, approximately 3.1 million U.S. adults have IBD.12 

There are two types of IBD: Crohn’s disease and ulcerative colitis. Although they are both inflammatory bowel diseases and share similar symptoms, they affect different areas of the GI tract and are not the same illness. 

  1. Crohn’s disease. Crohn’s disease (CD) can affect any part of the GI tract, from the mouth to the anus – although it most commonly affects the last part of the small intestine, called the ileum. CD causes inflammation of the digestive tract, which can lead to abdominal pain, severe diarrhea, fatigue, weight loss, and malnutrition. The inflammation can be continuous, or it might appear in patches and "skip" sections throughout the GI tract. In addition, inflammation can extend through the entire thickness of the bowel wall.13,14
  2. Ulcerative colitis. Ulcerative colitis (UC) is an inflammatory bowel disease that causes inflammation and ulcers (sores) in the colon. It affects the innermost lining of the colon and rectum. Ulcerative colitis is more common than Crohn’s disease. Individuals with UC will often have bloody, loose stool, urgency to go to the bathroom, an increased number of bowel movements, and abdominal pain and cramping.14,15

The symptoms of IBD range from mild to severe depending on the level of inflammation and where it occurs. People with IBD often experience times when the disease is quiet with few or no symptoms (remission), alternating with periods when the disease is active and causing symptoms.10,14 

What Causes IBD?

Although the exact cause of inflammatory bowel disease is unknown, it does involve an interaction between genes and the immune system. When the immune system is fighting off an invading virus or bacterium, it sometimes has an abnormal response that also causes it to attack the cells in the digestive tract, creating chronic inflammation. Heredity can also play a role in that IBD is more common in individuals who have family members with the disease and several genes are associated with the development of IBD.11,14

Diagnosis and Treatment for IBD

The diagnosis of IBD requires evaluation by a gastroenterologist – a medical doctor with specialized understanding of the digestive tract. Diagnosis can involve a combination of tests and procedures, including blood tests, stool samples, a computerized tomography (CT) scan, or an endoscopic procedure, such as a colonoscopy that takes tissue samples of the colon.5,17

The goal of treatment is to reduce the inflammation that triggers the signs and symptoms. This might lead to long-term remission and reduced risk of complications. IBD treatment usually involves a combination of tactics, including a change in diet, prescription drug therapy with immunosuppression, and sometimes surgery.18,19

Key Differences Between IBS and IBD 

The following isn't a complete list of the signs, symptoms, or differences between IBS and IBD, but it does provide a general idea of their basic distinguishing factors.2,20 

IBS

IBD

Classified as a syndrome, defined as a group of symptoms

Classified as a disease

Does not cause inflammation and rarely requires hospitalization or surgery

Can cause destructive inflammation and permanent harm to the intestines

There is no visible sign of abnormality during an exam of the GI tract

Signs of inflammation and damage are visible in the digestive tract during examination

Does not increase the risk for colon cancer or IBD

Increases the risk for colon cancer if the colon is affected by the disease

Blood in the stool and weight loss are NOT typical symptoms

Blood in the stool and weight loss can be symptoms

Treatments are prescribed to relieve specific IBS symptoms

Treatments are prescribed to reduce bowel inflammation and control symptoms

It's important to talk with a health care professional about any abdominal pain or chronic digestive symptoms you might be having. Working with a health care team can lead you to a diagnosis. Then you can learn how to manage your symptoms or begin treatment to improve your quality of life.

References

  1. What is IBS? International Foundation for Gastrointestinal Disorders. https://aboutibs.org/what-is-ibs/ [Accessed May 11, 2022]
  2. IBS vs IBD. Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/what-is-ibd/ibs-vs-ibd [Accessed May 11, 2022]
  3. Facts about IBS. International Foundation for Gastrointestinal Disorders. https://aboutibs.org/what-is-ibs/facts-about-ibs [Accessed May 13, 2022]
  4. Irritable bowel syndrome. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/irritable-bowel-syndrome/symptoms-causes/syc-20360016 [Accessed May 12, 2022] 
  5. What causes IBS? International Foundation for Gastrointestinal Disorders. https://aboutibs.org/what-is-ibs/what-causes-ibs/ [Accessed May 11, 2022]
  6. FAQs about IBS. International Foundation for Gastrointestinal Disorders. https://aboutibs.org/what-is-ibs/faq-about-ibs/ [Accessed May 13, 2022]
  7. Diagnosing IBS. International Foundation for Gastrointestinal Disorders. https://aboutibs.org/what-is-ibs/diagnosis-of-ibs/ [Accessed May 11, 2022]
  8. Treatment for IBS. International Foundation for Gastrointestinal Disorders. https://aboutibs.org/treatment/ [Accessed May 12, 2022] 
  9. 6 tips: IBS and Complementary Health Practices. National Center for Complementary and Integrative Health. https://www.nccih.nih.gov/health/tips/tips-ibs-and-complementary-health-practices [Accessed May 11, 2022]
  10. What is IBD? Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/what-is-ibd [Accessed May 12, 2022] 
  11. Facts about IBD. Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/sites/default/files/legacy/assets/pdfs/ibdfactbook.pdf [Accessed May 13, 2022]
  12. People with IBD have more chronic diseases. Centers for Disease Control and Prevention. https://www.cdc.gov/ibd/features/IBD-more-chronic-diseases.html. [Accessed May 31, 2022]
  13. What is Crohn's Disease? Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/what-is-crohns-disease [Accessed May 11, 2022]
  14.  Inflammatory Bowel Disease. American Gastroenterological Association. https://patient.gastro.org/inflammatory-bowel-disease-ibd/ [Accessed May 13, 2022]
  15. What is ulcerative colitis. Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/what-is-ulcerative-colitis [Accessed May 16, 2022]
  16. Diagnosing IBD. Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/what-is-ibd/diagnosing-ibd [Accessed May 13, 2022]
  17. Inflammatory Bowel Disease. Mayo Clinic https://www.mayoclinic.org/diseases-conditions/inflammatory-bowel-disease/symptoms-causes/syc-20353315 [Accessed May 12, 2022]
  18. Ulcerative colitis treatment options. Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/what-is-ulcerative-colitis/treatment-options [Accessed May 11, 2022]
  19. Crohn's disease treatment options. Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/What-is-crohns-disease/treatment [Accessed May 11, 2022]
  20. Inflammatory bowel disease vs irritable bowel syndrome. Crohn's and Colitis Foundation. https://www.crohnscolitisfoundation.org/sites/default/files/2019-10/ibd-and-IBS-brochure-final.pdf [Accessed May 12, 2022]