❗️DISCLAIMER❗️ This article is for information only. It is not intended to constitute or be a substitute for professional medical advice, diagnosis, or treatment.

Inflammatory Bowel Disease (IBD) is sometimes confused with Irritable Bowel Syndrome (IBS). “IBS” and “IBD” may sound similar, but the two acronyms stand for two very different conditions that affect the digestive tract. While they may have some similar symptoms, IBS and IBD are not the same, and they require very different treatments.

Syndrome vs disease

  • IBS

In IBS, “S” stands for syndrome. In medical terms, a syndrome is a group of symptoms occurring together that characterise a particular condition. Often, there is no identifiable cause as in case of IBS. IBS is classified as a functional gastrointestinal disorder, which means there is some type of disturbance in bowel function.

Around 1 in 5 Australians suffer from IBS. Typically, the unpleasant symptoms of IBS include abdominal pain, bloating, mucus in the stools, and either diarrhoea, constipation or a mixture of both. Its more common in women than in men and symptoms tend to first occur in early adulthood.

  • IBD

In IBD, “D” stands for disease. A disease is a condition that prevents the body, or part of it, from functioning normally and is usually characterised by a group of symptoms and signs. There are currently 100,000 people in Australia with Crohn’s disease or ulcerative colitis and this number is expected to rise into the future (link).

IBD is characterised by prolonged inflammation in various parts of the digestive tract. There are two subtypes of inflammatory bowel disease: Crohn’s Disease (CD) and ulcerative colitis (UC). UC specifically affects the large intestine (or colon) whereas CD can affect any part of GI tract.

Causes & Risk factors of IBS and IBD

The exact causes of IBS and IBD still remain incompletely understood and are the subject of ongoing clinical research. Genetics and family history are thought to play part in both.

While the cause of IBS is still uncertain, some of the risk factors thought to be involved in IBS include gastrointestinal infections, food intolerances and sensitivities, antibiotics, genetics – family history of IBS & emotional traumas or mood disorders, such as depression and anxiety.

IBS is thought to be related to hypersensitivity of the gut and the nerve cells that are within the gut. This in turn can be worsened by anxiety or depression or stress. You may have heard of gut-brain connection or gut-brain axis and IBS is inherently linked with this concept. The GI tract is second to only the nervous system in terms of how many nerve cells that it actually contains and if these nerve cells are hyperactive or overly sensitive to stimuli then you get the symptoms of IBS.

IBD has several risk factors, including genetic predisposition and is characterised by an abnormal immune repones & inflammation in the GI tract. These risk factors could be triggered by environmental and lifestyle factors including like stress, disturbances in composition and function of the gut microbiota (dysbiosis) and the Western diet.


In IBS, chronic, low-grade, subclinical inflammation has been implicated and is thought to perpetuate the symptoms of IBS. Unlike the previous reports in IBS patients, routine biopsies did not reveal abnormalities, in recent times subtle changes have been reported with the help of modern techniques.

In IBD, the body’s immune system reacts abnormally to specific triggers including biological (virus/bacteria or genetic component) and/or environmental – foods, stress episodes, smoking and alcohol. Such chronic abnormal immune response then results in damage to the gastrointestinal tract – weakening the gut barrier functions over time and negatively affecting the gut microbiota further adding the fuel to the fire of inflammation.


A noteworthy difference between these two conditions is in the symptoms. Two IBS patients can experience very different symptoms, whereas patients with CD or UC tend to have one prescriptive set of symptoms.

  • IBS:

IBS symptoms can vary from patient to patient. People with IBS are divided into 3 subcategories, depending on the variations in their bowel movements – diarrhoea (IBS-D), constipation (IBS-C) or both/mixed types (IBS-M).


  • Abdominal cramping/pain
  • Diarrhoea
  • Constipation
  • Mixed – Diarrhoea & Constipation
  • IBD:

Crohn’s Disease (CD) and Ulcerative Colitis (UC) share a lot of common symptoms, but they are not exactly identical.

CD can affect any part of the digestive tract and lesions can appear anywhere from the mouth to the rectum. However, it is most commonly found in the small intestine.

CD symptoms:

  • Mouth sores
  • Loss of appetite and weight loss
  • Pain or leakage near anus (perianal fistula)

Since CD mostly affects the small intestine, that is responsible for absorbing nutrients from your meals, CD flares cause inflammation and prevents the small intestine from doing its job putting patient at risk of nutrient deficiencies. Also, the lesions can cause scar tissue and can in turn have long-term consequences for digestive health. While surgery can remove an affected area, lesions can then appear in other parts of the gastrointestinal tract.

UC only affects the colon (large intestine) and symptoms include:

  • Blood/pus in the diarrhoea
  • Rectal pain
  • Urgent need to defecate
  • difficulty to defecate despite urgency

Several litres of water are flushed through a normal colon every day. This process assists fibre in the stool to absorb toxins so they can be flushed out from the body. However, an UC during flare up, inflammation can prevent water from entering and exiting the colon normally, leading to loose water stools.


While some treatments for IBS and IBD cross over, there are some important differences.

  • IBS:

IBS is a functional condition with no apparent damage to the gastrointestinal tract. It is not life threatening and doesn’t cause disease. IBS is debilitating and treatments focusses on managing symptoms and improving quality of life. Most common treatments include:

  • Dietary intervention that identifies food triggers and a person’s individual threshold for their triggers. The Monash University low FODMAP diet is the most well researched and evidenced dietary intervention for IBS
  • Empirical treatments involve interventions that directly treat a symptom. For example, taking Kfibre to assist dietary constipation.
  • Hypnotherapy is well researched as effective for addressing the miscommunication of the gut brain axis and has been shown to be as effective as a low FODMAP diet for improving IBS
  • IBD:

IBD is an inflammatory autoimmune condition that damages the gastrointestinal tract. Treatment is focussed on reducing inflammation and preventing complications.

  • Medications are central to management of IBD and may include anti-inflammatories, immunosuppressants, biologic medications, antibiotics and steroids to reduce inflammation and damage. To manage symptoms, anti-diarrhoea medication and pain relief may be recommended.
  • Diet intervention can be used to manage symptoms, meet nutritional needs and prevent deficiency. Often during a flare up, a low residue diet or enteral nutrition may be recommended. There is emerging research showing that a diet called the Crohn’s Disease Exclusion Diet (CDED) including partial enteral nutrition may help with remission in people who are not responding to medication.
  • Surgery may be recommended in cases that are not responsive to medication. For UC a total colectomy removes the colon, effectively “cures” the condition. With CD, up to two thirds of people will require at least one surgery. However, surgery does not cure CD as it can come back in another part of the gastrointestinal tract.

Gut microbiome

There is growing evidence that the compositions of our gut bacteria influences health and diseases, including IBS and IBD. Disturbances in the gut microbial composition and function, a state known as microbial dysbiosis is associated with both IBS & IBD.

Scientists are currently working on investigating just exactly how the microbiota can influence symptoms in IBS. Research into the gut microbiome indicates that specific bacteria may contribute to IBS-C type. For instance, IBS-C involves increase in the levels of Methanobrevibacter smithii, that is associated with higher production of methane, a gas known to slow the transit of stool through the gut.

Interestingly, people with IBS-D or IBS-M types may have lower levels of methane producing bacteria in their gut. Research also indicates that they may have depleted populations of microbes that produce butyrate. Butyrate is extremely crucial short-chain fatty acid for the human gut as it provides energy for the cells of the gut lining. Thus, butyrate production is critical in helping maintain the integrity of the gut lining and preventing inflammation.

Reduction in the butyrate producing microbes is also reported in IBD patients. Additionally, depleted short chain fatty acid (SCFA) levels is often associated with gut inflammation in IBD. A number of research studies has identified elevated levels of pathogenic microbes including E. coli in IBD patients. Furthermore, researchers have noted that IBD patients experiencing a flare tend to have lower levels of probiotic or beneficial bacteria. People with IBD for instance tend to have lower levels of Faecalibacterium prausnatzii, beneficial bacteria that protect gut from inflammation. It has also been suggested that specific pattern of dysbiosis or a negative shift in the composition and function of the microbiome may participate in triggering IBD.

To close:

IBS and IBD are two very different illnesses. It is vital to distinguish these two different gut conditions. While both are chronic, the overall treatment and prognosis are very different. An important differentiation between IBS and IBD are the associated health risks.

Both IBS and IBD can cause anxiety, depression and significantly reduce a person’s quality of life. IBD significantly increases serious disease risk, whereas IBS does not. IBD is linked to serious complications and health risks including malnutrition, weak joints and bones, ulcers, Parkinson’s and colon cancer. Making it important to consult your doctor if you experience persistent digestive symptoms, especially if they include red flags like weight loss or bleeding.

By Dr Tanvi Shinde, PhD & Contributions by Joanna Baker (APD | RN)