Inflammatory Bowel Disease (IBD) vs. Irritable Bowel Syndrome (IBS)

Both irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) can cause problems with digestion, including diarrhea and/or constipation, abdominal pain, and bloating. However, while the names are similar, they are completely different conditions. There are more differences between them than there are similarities.

This article will cover the two conditions and how they differ, including signs and symptoms, treatments, and extraintestinal complications (those occurring outside the intestines).

Key Features of IBD vs. IBS

IBD is a disease that causes inflammation in the digestive system and in other parts of the body. IBS is a disorder of gut-brain interaction. Many of the differences between them come from this fundamental understanding of the nature of each condition. 

What Is IBD?

IBD includes Crohn's disease, ulcerative colitis, and indeterminate (or undefined) colitis. There also are differences among the three types.

Crohn’s disease causes patchy inflammation that can occur anywhere in the digestive tract. Ulcerative colitis causes contiguous inflammation (inflamed areas are touching or close together) in the colon. Indeterminate colitis usually affects the colon like ulcerative colitis but also has some symptom overlap with Crohn’s disease, which makes diagnosis difficult.

IBD is a chronic, immune-mediated condition. It is thought to begin because of a complex interaction between genetic and environmental factors. This is, however, not settled science, and there may be a number of factors that contribute to the development of the condition.

It’s thought that the immune system reacts in an inappropriate way, leading to the inflammation that causes the signs and symptoms of IBD. The immune system gets activated and targets the intestinal tract and, sometimes, other parts of the body as well.

What Is IBS?

IBS is caused by a disruption in the communication between the central nervous system (which includes the brain and spinal cord) and the enteric nervous system (part of the peripheral nervous system that controls gastrointestinal behavior, or the gut). If there’s a disorder in the way the two communicate, it could lead to the symptoms that are common in IBS.

The causes of IBS also aren’t well understood. There is also variability in IBS symptoms, with some people experiencing either diarrhea or constipation as their main symptom and others having a combination of the two.

IBS

The different types of IBS are:

• IBS with predominant constipation (IBS-C)
• IBS with predominant diarrhea (IBS-D)
• IBS with mixed bowel habits (IBS-M)
• Unclassified IBS (IBS-U)

IBS and IBD Symptoms

One of the reasons that IBS and IBD are often confused is because of their signs and symptoms, which can overlap. However, there are symptoms of IBD that don’t occur with IBS. In addition, there are signs and symptoms that occur with Crohn’s disease and not ulcerative colitis, and the reverse.

The symptoms that could occur either with IBS or IBD include:

• Abdominal pain and/or cramping
• Bloating/distension 
• Constipation
• Diarrhea
• Mucus in the stool
• Urgent bowel movements
• Worsening of symptoms during menses
  

The symptoms that occur with IBD but not with IBS include:

• Fatigue
• Fever
• Loss of appetite
• Rectal bleeding
• Weight loss 
  

IBS may also cause alternating diarrhea and constipation.

Where Is the Pain in IBD vs. IBS?

Both IBS and IBD may cause abdominal pain. The way people experience pain is individualized, but there might be some similarities in where pain is located and what it feels like.

In IBS, the pain may be anywhere from mild to severe, and the abdomen may also be tender to the touch. IBS-C might cause pain that’s more frequent, more bothersome, and interferes with daily life more often than with IBS-D. In IBS-C and IBS-M, the pain might also be more widespread across the abdomen.

Abdominal pain is common in IBD. Pain is often felt when the disease is active (during a flare-up), with more than 80% of people having abdominal pain at least once a week. Between flare-ups, 62% of people reported pain.

In ulcerative colitis, pain tends to feel crampy and is located in the lower abdomen. It may get better after having a bowel movement.

In Crohn’s disease, pain is commonly felt in the lower right side of the abdomen, but it could appear in any part, or even throughout the abdomen. The pain may get worse after eating. In complicated Crohn’s disease, there could also be pain in other areas, such as the area around the anus (the perianal area).

Both IBD and IBS cause abdominal pain. Because people can have both conditions, it could be difficult to figure out which one is causing the pain.

Causes of IBD and IBS

The causes of both IBS and IBD are still poorly understood. Researchers are finding some clues as to why people may develop these disorders. However, it’s likely that there are many factors that work together as causes, and they are probably different from person to person.

Causes of IBS

IBS is a disorder of gut-brain interaction. This means there is a disruption in how the gut and the brain connect and communicate.

The causes of IBS can be due to several other factors. Some of the things that have been associated with developing IBS include:

• A disordered gut microbiome (the balance of microbes in the gut)
• Bacterial infection
• Food sensitivities
• Genetics
• Mental health conditions
• Small intestine bacterial overgrowth
• Stressful events in childhood
  

One of the key differences between IBS and IBD is the presence of inflammation. IBD always causes inflammation, and IBS is often not associated with inflammation.

However, some research shows that there could be low-grade subclinical inflammation in IBS, meaning that it’s not visible on a colonoscopy. It’s still unclear whether or how inflammation could play a role in IBS.

Causes of IBD

The causes of IBD aren’t fully understood, but many theories exist. It’s generally thought to be a genetic condition that is triggered by environmental factors. This means genes are associated with it, but not everyone with those genes develops the disorder. Some people with a genetic predisposition may encounter a trigger or triggers that cause IBD to develop.

IBD is an immune-mediated disease, meaning the immune system plays a role. Inflammation can be an appropriate response the immune system produces in certain circumstances, but the body is using inflammation inappropriately in IBD.

In general, it’s thought that the immune system reacts to a change, and the development of IBD begins. Some of the things that could contribute to this cascade of events may include: 

• Appendectomy (surgery to remove the appendix; increases the risk of Crohn’s disease but decreases the risk of ulcerative colitis)
• Disruption in the gut microbiome
• Dysregulation of the immune system
• Food sensitivities or intolerances
• Genetics
• Medications
• Psychological stress
• Smoking
  

IBD vs. IBS Diagnosis

IBD is generally diagnosed after taking a history (including signs and symptoms) and performing some tests. There’s usually no one test that can give a diagnosis, although a colonoscopy can provide a lot of information if there is inflammation or other signs of IBD (such as scarring) can be seen.

The tests that might be used to diagnose IBD include:

• Barium enema
• Blood tests
• Capsule endoscopy
• Colonoscopy
• Computed tomography enterography (CTE) scan
• Intestinal ultrasound
• Sigmoidoscopy 
• Stool tests (for blood and infections or parasites and for fecal calprotectin)
• Upper endoscopy
• Upper gastrointestinal (GI) series
• X-rays
  

IBS is diagnosed with a set of standards called the Rome criteria. To be IBS, there must be recurrent abdominal pain on average at least one day/week in the last three months, associated with two or more of the following criteria:

1. Related to defecation
2. Associated with a change in the frequency of stool
3. Associated with a change in the form (appearance) of stool
   

These criteria must be fulfilled for the last three months, with symptom onset at least six months prior to diagnosis.

Complications With IBD and IBS

Another key difference between IBS and IBD has to do with complications. In general, IBS is not a risk factor for serious complications such as cancer. IBD, however, can be connected to extraintestinal complications in some people.

IBS

IBS is a chronic condition, and signs and symptoms will come and go. It does not increase the likelihood of developing colon cancer. It’s not a life-threatening condition. It can, however, significantly reduce your enjoyment of life, including family time and socializing, and interfere with work.

People with IBS who have constipation may have a greater risk of stool becoming impacted. If they restrict their diet to avoid symptoms, there may be a risk of becoming deficient in vitamins or minerals. Those who have diarrhea with their IBS may be at risk for dehydration. There may also be an increased risk of developing hemorrhoids (inflamed and swollen veins around the anus or lower part of the rectum).

People who have IBS are also at risk of developing mental health conditions, such as anxiety and depression.

IBD

IBD is associated with several complications inside and outside the digestive system. Complications can differ between Crohn’s disease and ulcerative colitis.

Complications within the digestive system that could occur with Crohn’s disease include:

• Abscess (a pocket of pus in the body)
  
• Fistula (an abnormal connection between two organs)
• Increased risk of small intestine cancer (but this is rare) and colon cancer (for those who have inflammation in the colon)
• Stricture (a narrowing of the intestine)
  

Complications that can occur in the digestive system with ulcerative colitis include:

• Increased risk of colon cancer
• Perforation (a hole in the intestinal wall)
• Toxic megacolon (a life-threatening condition in the large intestine)

Extraintestinal manifestations are complications that occur outside of the digestive system. In Crohn’s disease and ulcerative colitis, these can include:

• Arthritis
• Bone disorders (including avascular necrosis and osteoporosis)
• Gallstones
• Increased risk of blood clots
• Eye disorders (including uveitis, scleritis, and episcleritis)
• Kidney stones
• Liver disease (such as primary sclerosing cholangitis)
• Mouth ulcers
• Skin disorders (including pyoderma gangrenosum and erythema nodosum)
  

Treatment for IBS and IBD

Another key difference between IBS and IBD regards treatment. For the most part, they are treated with different medications. There could be some overlap when it comes to lifestyle changes.

IBS

Prescription medications may be used to treat different types of IBS. These medications could include:

• Antibiotics for IBS-D, such as Xifaxan (rifaximin)
• Antispasmodics, like dicyclomine, hyoscyamine, and hyoscine
• Intestinal secretagogues for IBS-C, including Linzess (linaclotide), Amitiza (lubiprostone), Trulance (plecanatide), Ibsrela (tenapanor)
• Mu- and kappa-opioid receptor agonist/delta-opioid receptor antagonist for IBS-D, such as Viberzi (eluxadoline)
• Serotonin type-4 receptor (5-HT4) agonists for IBS-C, like Zelnorm (tegaserod)
• Serotonin (5-hydroxytryptamine; 5-HT3) antagonists for IBS-D, including Lotronex (alosetron) and Zofran (ondansetron)
• Tricyclic antidepressants, such as Elavil (amitriptyline), Pamelor (nortriptyline), Tofranil (imipramine), and Norpramin (desipramine)

Diet is another key component of IBS treatment. How diet is used is often individualized but may include a low fermentable oligosaccharides, disaccharides, monosaccharides, polyols (FODMAP) diet. Other types of diets may be used individually, on the advice of a dietitian.

Mind-body therapy is also sometimes recommended. This can include gut-directed psychotherapies such as cognitive behavioral therapy (CBT) and gut-directed hypnotherapy. Peppermint oil supplements may also be used.

Other lifestyle changes or supplements may also be used, but there is less evidence that they will be effective.

IBD

Many of the medications for IBD may be approved for use in both Crohn’s disease and ulcerative colitis, with a few exceptions. These diseases are treated separately when it comes to medication approvals.

Some of the medications that might be used include:

• Aminosalicylates (5-ASA), including sulfasalazine, mesalamine, olsalazine, and balsalazide, which are used for ulcerative colitis
• Antibiotics (in specific situations)
• Biologics and their biosimilars, such as Cimzia (certolizumab), Entyvio (vedolizumab), Humira and others (adalimumab), Remicade and others (infliximab), Simponi (golimumab), Stelara (ustekinumab), Tysabri (natalizumab)
• Immunomodulators, including Imuran (azathioprine), 6-mercaptopurine, cyclosporine, and tacrolimus
• Corticosteroids (prednisone)
• Janus kinase (JAK) inhibitors, such as Xeljanz (tofacitinib) and Rinvoq (upadacitinib) for Crohn’s disease
  
• Sphingosine 1-phosphate (S1P) receptor modulator, like Zeposia (ozanimod)

Surgery may also be used to treat IBD. In ulcerative colitis, this may include ileostomy or ileal pouch surgery, both of which involve the removal of the colon and/or rectum (colectomy).

In Crohn’s disease, a resection to remove an affected part of the intestine is often used, along with colostomy, ileostomy, and stricture surgery. Other types of surgery may be needed to treat intestinal or extraintestinal complications.

In addition to medications and surgery, people with IBD may also make lifestyle changes to manage symptoms inside and outside the gut, including diet, exercise, and mind-body practices. 

Prevalence of IBS and IBD

IBS is a common condition. It may affect between 4% and 5% of people in the United States, United Kingdom, and Canada. It is more commonly diagnosed in people under age 50 and in females more so than males.

IBD is also common. It may affect between 2% and 3% of people in the United States. It used to be thought of as a disease of Western countries. However, it is increasingly becoming a worldwide disease as it becomes more common in Asia, Africa, and South America.

How Stress Relates to IBS and IBD

Stress does not cause IBS or IBD. However, stress can make symptoms worse for some people.

The relationship between digestive conditions and stress is often described as bidirectional. This means that stress can worsen the condition but also that the condition itself causes stress.

Stress relief is increasingly being used as an adjunct therapy for digestive conditions. People who live with diseases and conditions that affect the digestive system will want to check with their healthcare providers about help for their mental health.

Can IBD Lead to IBS?

It’s possible for people to have both IBS and IBD at the same time. How these conditions may overlap is still not well understood. For some people with IBD who still have symptoms even when in remission, IBS may be the cause.

IBD is associated with other immune-mediated conditions. These can include asthma, chronic bronchitis, celiac disease, multiple sclerosis, pericarditis, psoriasis, and rheumatoid arthritis.

Summary

IBS and IBD have similarities in their symptoms, but there are specific and important differences. A diagnosis is important in the treatment and management of these conditions because they are not treated with the same medications.

The two conditions can occur together, further complicating treatment. There is still much more to learn about how the two conditions may overlap and affect one another.