IBS vs. IBD: Understand The Key Differences

Many people get irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD) confused – it’s a common misunderstanding, as they both affect the gut and share some similar symptoms. Sometimes, you can even have both of these gastrointestinal (GI) disorders¹ at the same time.

Although they can be difficult to distinguish, IBS and IBD are different conditions. They have different disease processes, and their symptoms and long-term outcomes can vary significantly.

Understanding the differences between these conditions is crucial for accurate diagnosis and treatment since they require different approaches.

What are IBS and IBD?

IBS

Irritable bowel syndrome (IBS) is a disorder that affects the lower gastrointestinal area, including the colon, large intestine, and small intestine. If you have IBS, you may experience diarrhea or constipation – sometimes, you might even have both.

There are different types of IBS, categorized according to their symptoms:

• IBS-C – Constipation is the main symptom, resulting in fewer bowel movements, and you will likely strain when passing them.

• IBS-D – Diarrhea is the main symptom, characterized by frequent bowel movements and over a quarter of the stools you pass being loose. 

• IBS-M – Alternating symptoms of constipation and diarrhea. Your stool may be loose and watery on some days or hard and lumpy on others.

IBD

Inflammatory bowel disease (IBD) is a term that represents several gastrointestinal conditions that cause swelling and inflammation of the intestines. The most common conditions are ulcerative colitis and Crohn's disease. These conditions are genetic for many patients, but no single gene is known to be the cause. The severity of the disease depends on multiple genetic abnormalities and the effect of microbes on your immune system.  Like IBS, diarrhea is the most common symptom of IBD.

Other common symptoms of IBD include:

• Blood in your stool

• Fever

• Abdominal cramps

• Loss of appetite

• Anemia

• Extreme weight loss

• Loss of bodily fluids

• Blocked bowels or difficulty passing bowel movements

What are the differences between IBS and IBD?

While IBS and IBD share some symptoms, they are distinct conditions with a number of differences between them, including:

• IBD is a disease, while IBS is categorized as a syndrome or group of symptoms. 

• Doctors can detect IBD with diagnostic imaging, while IBS is undetectable during a colon exam. 

• IBD can result in high levels of inflammation and permanently damage the intestines, while IBS does not lead to inflammation and rarely requires surgery or hospitalization. 

• While IBD increases the risk of colon cancer, IBS is not known to increase the risk of developing either colon cancer or IBD. 

• IBD affects less than 1%² of the global population, while IBS is more prevalent, affecting up to 15%³. 

• Both conditions can affect individuals of all ages, but IBD is more prevalent in younger people. 

• The conditions can also affect both genders. Where IBD is equally common in women as in men, women are two times⁴ more likely to have IBS.

What causes IBS and IBD?

IBS

Some IBS patients⁵ can experience microscopic areas of inflammation. The causes are not known, but it is suggested that they range from abnormal bowel contractions (due to triggers such as stress or foods) to hyperreactivity of bacterial gut infections to delayed or accelerated transit of contents via the GI tract (constipation or diarrhea).

IBD

The exact cause(s) of IBD, including its various types,  remains unknown, but researchers suggest² that it may be caused by a malfunctioning of the immune system in the bowel tissue, a genetic predisposition, and/or an individual’s response to gut microorganisms.

How are IBS and IBD diagnosed?

IBD

A doctor can diagnose you with IBD by examining whether you have physical intestinal damage. The diagnosis can be undertaken through CT or MRI scans, blood and stool tests, or a colonoscopy. During a colonoscopy, your doctor may remove a small tissue sample for further analysis in a process called a biopsy. These tests enable your doctor to accurately establish whether you have IBD and in what form if the tests show that you have ulcers and inflammation.

IBS

Doctors can diagnose you with IBS using the Rome criteria⁶. You are considered to have IBS if you experience pain in your belly for at least one day a week for three consecutive months, and the belly pain is accompanied by two of the following symptoms:

• Bowel movement that either increases or improves the pain

• Change in the appearance of your stool

• Increase or decrease in the frequency of your bowel movements

The Rome criteria can be used solely to diagnose IBS, but your doctor may also recommend that you undergo testing to determine whether there is inflammation or bleeding in your digestive tract, especially if you have other symptoms that point to a potential diagnosis of IBD.

What other conditions are similar to IBS?

IBS has similar symptoms to other conditions, such as Crohn's disease and colitis, including ulcerative colitis and microscopic colitis.

Ulcerative colitis has many of the same symptoms as IBS, such as:

• Diarrhea

• Mucus in stool

• Chronic abdominal pain

• Bowel urgency

Shared symptoms between microscopic colitis and IBS include:

• Chronic diarrhea

• Abdominal pain or cramping

• Fecal incontinence

However, colitis is different from IBS in that it is generally an inflammation of the colon, whereas IBS does not lead to inflammation.

Crohn's disease⁷ is also similar to IBS. The two conditions share very similar symptoms that can make them difficult to distinguish from one another. This can even lead to misdiagnosis or the wrong treatment being recommended.

Both IBS and Crohn’s disease cause:

• Abdominal pain

• Abdominal distension

• Diarrhea

However, you may have Crohn’s disease if you have some or all of the following symptoms:

• Fatigue

• Bleeding

• Weight loss

• Fever

When should you see a doctor?

Contact your doctor if you notice a new or sudden change in any IBS or IBD symptoms. You should monitor your condition for symptoms such as:

• Difficulty swallowing 

• Anemia 

• Rectal bleeding

• Unexplained vomiting 

• Persistent pain that continues even after bowel movements

The lowdown

IBS and IBD are different gastrointestinal conditions that both affect the gastrointestinal tract. As they share some similar symptoms, it can be difficult to distinguish between the two. IBD typically causes swelling and inflammation of the gastrointestinal tract, whereas IBS is a term that refers to a range of symptoms affecting that gut that occur together. The cause of each condition is not yet known.  If you experience any of the symptoms of IBS or IBD, it is important to contact your doctor to seek an accurate diagnosis. The correct diagnosis is crucial because the conditions require different treatments.