IBS vs IBD - Is there a difference?

By Ryan Warren, MS, RDN, CDN

IBS vs IBD - Is there a difference? 

Irritable Bowel Syndrome and Inflammatory Bowel Disease affect millions of Americans. 25 to 45 million people in the US suffer from Irritable Bowel Syndrome while an additional 3 million suffer from Inflammatory Bowel Disease. While these two gastrointestinal conditions have some similar symptoms, IBS and IBD are not the same and require different treatments. 

Let’s define the terms - IBS and IBD 

Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are two gastrointestinal conditions that are often mistaken for one another. That’s understandable because the abbreviated names are almost identical. While the acronyms are similar, these two gastrointestinal conditions have distinct differences that set them apart from one another. 

IBS is a functional gastrointestinal disorder of the lower gastrointestinal (GI) tract that affects the small and, more predominantly, large intestines.  

IBD, on the other hand, refers to a set of diseases that cause chronic inflammation of the digestive tract, namely Crohn’s disease and ulcerative colitis. IBD also adversely affects your immune system; an incorrect inflammatory response to environmental triggers essentially causes the body to “attack” itself.  

While Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD) are different and not synonymous, these conditions can overlap with one another in terms of symptoms, triggers and even some forms of treatments. As patients and clinicians, how do we navigate this tricky dichotomy? 

IBS vs IBD Symptoms: Parallels 

Aside from the fact that they simply sound similar, IBS and IBD are conditions that also have similar clinical manifestations. Here are some common signs and symptoms that characterize IBS: 

  • Flatulence (excessive gas) 
  • Early satiety (feeling full quickly during a meal) 
  • Nausea 
  • Abdominal pain or discomfort 
  • Constipation 
  • Diarrhea or Involuntary Bowel Movement 
  • Tenesmus (feeling of having to pass stool with the inability to do so) 

As luck would have it, many of these are IBD symptoms too, which is why it can be challenging to determine the root cause of the symptoms. 

Next, let’s discuss each condition in detail. 

Inflammatory Bowel Disease (IBD) 

Inflammatory bowel disease (IBD), which as previously mentioned includes Crohn’s disease and ulcerative colitis (UC), is a chronic, systemic, relapsing, immune-mediated inflammation of the gastrointestinal tract. These Inflammatory Bowel Diseases are estimated to affect 3 million Americans (which roughly equates to 1.3% of the population), and millions more across the globe. While the exact etiology of Inflammatory Bowel Disease (IBD) is not definitively known nor completely understood, scientists and clinicians hypothesize that it is likely the product of a complex network of factors, which include: 

  • Genes or Family History (some people have a hereditary predisposition) 
  • Environment (which includes dietary factors and stress!) 
  • Immune system (which can be overactive or hypersensitive) 

IBD may result when certain people with susceptibility (based on genetic makeup) come into contact with certain environmental triggers. Just like other diseases, IBD is more likely to affect someone if it is present in their family history. The external factors, in turn, prompt a dysfunctional and ongoing immune response that results in chronic inflammation of the GI tract. In essence, it’s like the perfect storm. 

Inflammatory Bowel Diseases 

Ulcerative Colitis 

Ulcerative Colitis is an Inflammatory Bowel Disease that is characterized by inflammation and sores (ulcers) in the colon. The exact cause of Ulcerative Colitis remains unknown, however it is believed to be related to an abnormal immune system response that essentially causes our body’s natural defenses to turn against us.  

Crohn's Disease 

Crohn's Disease is an Inflammatory Bowel Disease that is a chronic, incurable condition characterized by inflammation of the digestive tract, which can affect multiple layers of tissue. Crohn's Disease can affect any part of the gastrointestinal system from mouth to anus, which means it has the potential to cause symptoms anywhere along this path.  

Every patient’s experience with IBD is separate and unique; as a result, it is not a one-size-fits-all type of disease. Furthermore, there are essential differences between Crohn’s disease and ulcerative colitis. That said, there are a multitude of common symptoms that characterize IBD, including irregular bowel movements (often, diarrhea) and abdominal pain. IBD can also increase the risk of colon cancer.  

Beyond these common symptoms, patients with IBD may also experience the following: blood in stools, bowel obstruction (depending on the location of the inflammation), as well as “extraintestinal” manifestations of active inflammation (weight loss, anemia, joint pains, skin rashes, fevers etc.). 

Given the fact that IBD is chronic and therefore not curable, management of the disease can involve a complex treatment protocol. The goal of therapy is to reduce inflammation and help patients manage their symptoms on a day-to-day basis. This can involve antibiotics, steroids, immunosuppressants, biologic meds as well as over the counter remedies (e.g., anti-diarrheal, anti-spasmodic) and lifestyle modifications (think: diet and stress management!). In some severe cases, surgical options may also be explored. 

Even though there is no cure for IBD currently, doctors typically  suggest those suffering from an IBD is to focus on their food intake and follow diets such as the Mediterranean Diet or Low FODMAP diet. 

Digestive and Kidney Diseases Symptom Similarities 

Digestive and kidney diseases are two separate groups of chronic conditions that can sometimes mimic each other’s symptoms. It is important to get diagnosed with the help of a medical professional so you can know how best to treat your chronic condition. 

Irritable Bowel Syndrome (IBS) 

Just because a patient is diagnosed with IBD does not automatically mean they do not have IBS. The two are not necessarily mutually exclusive! That said, there are many patients who are diagnosed with IBS who do NOT have IBD. Patients with IBS suffer from a functional gastrointestinal disorder that primarily affects the lower parts of the GI tract - including both the small and large intestines. Like IBD, IBS is considered chronic and requires long-term management.  

While the signs and symptoms vary among individual sufferers, some of the most common include: irregular bowel movements (ranging from constipation to diarrhea), abdominal cramping, bloating, and gas. These symptoms can range from mild to severe. Luckily, however, unlike IBD, IBS does not harm or destroy the tissues that line the intestines. 

The medical community does not know precisely what causes IBS, but they think there are links between IBS and an exhausted immune system. Some commonly accepted theories and triggering factors include: dysfunctional nerves (in the GI tract), abnormal muscle contractions in the bowl (either too fast or too slow), microbial imbalances (which includes small intestinal bacterial overgrowth - i.e. SIBO) as well as infections. 

Much like in the case of IBD, diet and stress can play significant roles in triggering or exacerbating IBS symptoms. Certain foods can trigger IBS in some individuals and others experience IBS when they are stressed or anxious. That said, the converse is true as well. Dietary modifications can also play a key role in helping to manage both of these conditions and therefore optimize our patients’ nutrition status. Oftentimes, IBS management includes diet modification and stress reduction. Various medications, including anti-spasmodic and over the counter remedies such as Pepto Bismol and Tums, may also be used. 

So what comes next? The Diagnosis. 

If a new patient presents to a gastroenterology (GI) clinic reporting some of the classic symptoms listed above, the medical team will likely use a variety of different diagnostic tools and techniques to get a clearer picture of what is going on. Doctors might use one or more of the following tests to differentiate between IBS and IBD: 

  • Blood work to detect infection, anemia and/or inflammation 
  • Endoscopy (includes both upper endoscopies and colonoscopies) with biopsy, which allows the doctor to visibly detect inflammation, ulcers, bleeding and other irregularities that may be present in the GI tract. Biopsies, which are evaluated by pathologists, shed additional light on the presence of inflammation at the microscopic level. 
  • Fecal calprotectin, which is a specific marker of intestinal inflammation 
  • Imaging, such as CT or MR Enterography (MRE), X-rays, CT scans and MRIs; these provide more information about the extent of inflammation (i.e., does it extend through various layers of the gut?), presence of narrowing or strictures, and bowel obstruction. 
  • Hydrogen breath test to rule out bacterial overgrowth and/or sugar (lactose, fructose, sucrose) malabsorption 
  • Stool sample to assess for inflammatory markers, infectious pathogens, or bile salt 

Taken together, these assessments help doctors to diagnose IBD, IBS, or lack thereof! We’ll discuss IBD in greater detail up next. 

Is IBS the same as IBD: The Verdict 

Clearly, there are a lot of similarities between IBS and IBD; however, the answer to this question is, “no, they are not the same.”  

IBS and IBD are two unique and distinct etiologies. But, in reality, the convergence of these gastroenterological conditions as well as the inherent similarities makes the situation slightly more complicated. 

Research shows that approximately 40% of IBD patients report symptoms of IBS (e.g. flatulence, bloating, abdominal pain, bowel irregularities including both frequent loose stools and constipation), even when they are in remission (i.e., their IBD is inactive). When we are evaluating our IBD patients, we often have to think about what is causing their symptoms. In the absence of inflammation, it is highly likely that many reported gut symptoms may be triggered by overlapping IBS. And the prevalence of this overlap makes sense when we consider some of the common denominators for both IBD and IBS, including the following shared factors: intestinal dysmotility, visceral hypersensitivity, increased mucosal permeability (i.e., leaky gut), psychological distress and possibly microbial dysbiosis.    

In summary, IBD is a disease, whereas IBS is a syndrome. While they are not the same, the difference between the two can be a source of confusion for many because of the prevalence of similarities in clinical presentation. It is crucial, however, to be appropriately diagnosed (with either IBD, IBD or both!) to safely and effectively manage the condition. 

If you have further questions about IBD or IBD and are experiencing symptoms consistent with these conditions, we would highly encourage you to schedule an office appointment with your gastroenterologist so that they can take the appropriate next steps. 

How to treat IBS and IBD with a Low FODMAP Diet

A common suggestion by gastroenterologists is to follow a Low FODMAP diet. A Low FODMAP diet is an elimination diet that removes fermentable sugars called FODMAPS from your diet. These FODAMPS have trouble digesting in some people's guts which can cause uncomfortable symptoms.

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Ryan Warren, MS, RDN, CDN

Ryan Warren is a Registered Dietitian and Clinical Nutritionist (RDN) with a Masters of Science in Clinical Nutrition from New York University. She completed her Dietetic Internship at New York University (NYU Langone Medical Center) and has a Bachelor of Arts in Human Biology from Brown University. Ryan currently works at Weill Cornell Medicine at the Center for Inflammatory Bowel Disease where she specializes in providing personalized nutrition counseling to people with gastrointestinal issues, including Crohn’s Disease, Ulcerative Colitis, Irritable Bowel Syndrome (IBS), Small Intestinal Bacterial Overgrowth (SIBO), diverticulosis/diverticulitis, GERD, food sensitivities and intolerances, and a whole host of other conditions. Visit https://ryanwarrennutrition.com to learn more.