IBS vs IBD: What's the Difference?

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IBS vs IBD: What's the Difference?

Courtney Bennett

Written by Courtney Bennett

Courtney Bennett

Courtney Bennett

Dr. Courtney Bennett aims to simplify the complexities of modern medicine, enabling readers to make informed choices about their health. Her interests include reading, camping, hiking, painting, and photography.

September 26, 2019 / Read Time 6 minutes

Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD) are chronic conditions that affect the gastrointestinal tract (also known as the GI tract, intestinal tract, or digestive tract).

The GI tract is made up of hollow organs that stretch all the way from the mouth to the anus; it includes the:

  • Mouth

  • Esophagus

  • Stomach

  • Small intestine

  • Large intestine (including the rectum)

  • Anus

Both IBS and IBD are umbrella terms used to describe certain disorders of the digestive tract that vary in their presentation from patient to patient, but they are otherwise quite distinct.

IBDs are diseases that cause chronic intestinal inflammation, including Chron’s disease and ulcerative colitis.

IBS is a functional gastrointestinal disorder that causes changes in digestion and motility but does not cause physical damage.

This article will help you understand the similarities and differences between IBS and IBD.

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What is IBS?

Irritable Bowel Syndrome is a chronic disorder that describes a constellation of symptoms caused by the misfunctioning of the gastrointestinal tract. The symptoms and severity can vary wildly from person to person, with some people having episodes or flares followed by periods of remission, and some being afflicted by the symptoms daily.

One study conducted in 2001 that surveyed ~1,450 patients found that 57% suffered daily, 25% weekly, and 14% monthly. In a 2002 survey of 350 patients conducted by the International Foundation for Functional Gastrointestinal Disorders (IFFGD), over one third of patients rated their pain as extreme or very severe.

Rather than a clearly defined medical condition, IBS has often been called a diagnosis of exclusion. When other major diagnoses can be adequately excluded (e.g. Chron’s or ulcerative colitis, celiac disease, gallstones, cancer) and no damage to the gastrointestinal tract is visible, IBS is often diagnosed.

There is no consensus on the pathophysiology, or physiological cause, of IBS. Physicians generally credit a variety of factors that are thought to stem from a disruption or malfunction in the brain-gut communication channel including:

  • A recent stomach virus

  • Changes to the gut microbiome

  • Anxiety or depression

  • Severe stress

  • Increased visceral sensitivity

  • Impaired transit of intestinal gas

  • Genetic variation

The Rome Foundation manual says the following about functional gastrointestinal disorders: “Functional GI disorders are disorders of gut–brain interaction. It is a group of disorders classified by GI symptoms related to any combination of the following: motility disturbance, visceral hypersensitivity, altered mucosal and immune function, altered gut microbiota, and altered central nervous system processing.”

What are IBS Symptoms?

Symptoms of IBS include:

  • Changes in motility (i.e. diarrhea and/or constipation)

  • Bloating / distention of the abdomen, especially after eating

  • Abdominal pain or cramps

  • Urgency

  • Mucus in stool

  • Feelings of incomplete emptying during bowel movements

IBS is typically classified as one of three categories:

  • IBS-C. IBS-C is primarily characterized by constipation.

  • IBS-D. IBS-D is primarily characterized by diarrhea.

  • IBS-M. IBS-M (sometimes alternatively referred to as IBS-A) is characterized by a mix of both constipation and diarrhea.

What is IBD?

Inflammatory Bowel Diseases are mainly differentiated from Irritable Bowel Syndrome by their severity and physical presentation, as well as the lasting physical damage that is inflicted on the intestines.

While IBS can be debilitating, it does not cause visible damage (i.e. inflammation, ulcers) to the intestinal tract. IBDs, on the other hand, often cause severe, irreversible damage to the intestinal tract.

IBDs are autoimmune diseases, with the inflammation stemming from the digestive system being attacked by the body’s own immune system. IBDs primarily include Chron’s disease and ulcerative colitis.

Similar to IBS, the causes of IBDs are not very well understood either. Physicians and researches posit a combination of:

  • Bacterial contamination

  • A change in the immune system

  • Genetic variations

A majority of patients with an IBD have been observed to have defects in intestinal epithelial barrier function. The intestinal epithelium is a single-cell layer that forms the lining of the small and large intestine and acts as a barrier between the body and external elements that have been ingested.

It is a semi-permeable barrier that allows electrolytes, nutrients, and water to be absorbed, but acts as a barrier that keeps antigens, toxins, and microorganisms from passing through.

Alterations or defects that increase the permeability of the epithelium significantly increase an individual’s susceptibility to developing not only an IBD, but any intestinal disease.

It is commonly understood that autoimmune diseases are heavily influenced by genetics, however, the major influence of IBD development appears to be due to environmental factors.

Research suggests that autoimmune diseases have a higher prevalence in developed countries, with North America having the highest prevalence of Chron’s disease in the world. Some studies have shown that this may be due to the increased consumption of milk and animal proteins, as well as polyunsaturated fatty acids (found in corn and sunflower oil, soy beans, and some seeds and nuts), that is seen in developed countries.

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What are IBD Symptoms?

Chron’s disease and ulcerative colitis have similar symptoms, but they are diagnostically distinct. Chron’s disease is characterized by inflammation anywhere along the lining of the digestive tract, while ulcerative colitis causes chronic inflammation only in certain parts of the digestive tract, most often the colon or large intestine.

Symptoms of the IBDs include:

  • Diarrhea

  • Fever and fatigue

  • Abdominal pain and cramping

  • Blood in your stool

  • Reduced appetite

  • Unintended weight loss

  • Chron’s disease: thickening of the bowel wall

Diagnosing IBS vs. IBD

IBS is tricky to diagnose because there are no tests that can definitively indicate that you have it. IBDs, on the other hand, are often diagnosed based on visible damage to the intestinal track.

The damage is most often evaluated through a procedure known as a colonoscopy – this procedure involves the patient being sedated, and a thin flexible scope with a camera attached to the end being inserted into the rectum and into the intestinal tract. A gastroenterologist will often be able to diagnose an IBD based on visible damage and inflammation alone, but may take samples or biopsies as well in order to confirm the diagnosis.

Biopsies are a very effective diagnostic tool for distinguishing between Chron’s disease and ulcerative colitis as they each have distinctive inflammation patterns.

A recent technological advancement allows some physicians to perform a capsule endoscopy, a procedure which can examine the small intestine, which is unreachable by either colonoscopy or endoscopy. A capsule endoscopy involves the patient swallowing a pill sized wireless camera that takes pictures of the gastrointestinal tract.

If IBDs are ruled out, a diagnosis of IBS is much more likely.

Blood tests can also aid in diagnosing an IBD if there is an elevated white cell count or sedimentation rate, anemia, and/ or a vitamin B-12 deficiency. X-rays or magnetic resonance imaging (MRI) can be used to reveal additional complications that are the result of IBDs, such as abscesses, fistulae, or bowel obstructions.

Additional tests may be conducted in order to rule out other GI disorders such as:

  • Celiac disease: a blood test is conducted in order to diagnose or rule out celiac disease.

  • Lactose intolerance: oftentimes patients will be asked to restrict their intake of lactose for a short time and evaluate whether symptoms dissipate. If that elimination yields significant improvement, lactose intolerance can be diagnosed without further testing. However, a hydrogen breath test and lactose intolerance blood test may be completed as well.

  • Gastroparesis: a gastric emptying study can evaluate whether a patient is suffering from gastroparesis, a condition which affects the stomach muscles and prevents the stomach from emptying properly.

  • Small intestine bacterial overgrowth (SIBO): some physicians will conduct a hydrogen and/or lactulose breath test in order to diagnose SIBO, however, there is currently no universally accepted standard for hydrogen and lactulose levels. As such, some physicians will treat potential SIBO with antibiotics, in lieu of any diagnostic test, and evaluate improvements.

  • Ulcers: an endoscopy may be performed in order to inspect the stomach lining and part of the small intestine. Similar to a colonoscopy, a flexible scope with a camera on the end is inserted into the mouth and down the esophagus into the gastrointestinal tract. Additionally, stool samples may be taken in order to look for the presence of H. pylori – a bacteria that commonly causes ulcers.

  • Gallstones: an ultrasound of the gallbladder can determine whether a patient is suffering from gallstones.

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When to Contact a Doctor

While IBS is a serious condition, it is not life threatening.

However, similar conditions such as Inflammatory Bowel Disease (IBD) can have grave consequences to your health that worsen the longer they are left untreated.

If you are experiencing unintended weight loss, reduced appetite, fatigue, blood in your stool, or black, tarry stools in addition to the aforementioned IBS symptoms, you should contact your physician right away.

Book an appointment to talk to a PlushCare doctor today.

Read more from our IBS Series:


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