Difference between Crohn’s and IBS

difference between crohn's and ibs


The difference between Crohn’s disease and IBS is former a transmural (across the entire wall) inflammation of the gastrointestinal (GI) tract anywhere from mouth to anus. In 30% of cases, there is granulosa (tumor) formation. It is a form of IBD (Inflammatory bowel disease), the other being Ulcerative Colitis (UC). The latter (IBS-Irritable Bowel Syndrome)  is a functional digestive disorder. It is characterized by altered bowel movement and abdominal pain accompanied by bloating. In this topic will know in detail the difference between Crohn’s disease and IBS.

Crohn’s disease

This disease is caused by the inflammation of all the layers (transmural)  of the gastrointestinal tract(GI) in segments. This is also called skip lesions (inflammation in segments). The most affected part is both the small intestine (ileum) and large intestine (colon) or maybe both. It generally affects young people between the ages of 20 years to 30 years. It is characterized by relapse and remission. Crohn’s disease is more prevalent in white people and females.


The  etiology of Crohn’s disease is not exactly known however the following are thought to be the causes :

Immune involvement

The GI  tract efficiently manages substances that can cross the epithelial boundary and get into blood circulation. This is done by the secretion of proteins like defensin by the epithelial cells.

These proteins keep the bacteria and other toxic substances away from the circulation. Goblet cells produce mucin which also forms a protective barrier.

In patients with Crohn’s disease, both defensin and mucin are found in low levels. This protective barrier is lost and bacteria can easily translocate across the epithelial tissue. These bacteria along with certain other chemicals released by the WBCs (Interleukines) cause acute inflammation of the GI tract lining.

Genetic factor

Certain genes are passed on from the family members having IBD. It tends to run in the family. Another gene NOD2 its mutation causes IBD.

Environmental factors

Prior infection by viruses, or bacteria (tuberculosis) can cause Crohn’s disease.

Diet and smoking also pose a risk for Crohn’s disease

The use of antibiotics and NSAIDs (non-steroidal anti-inflammatory drugs) can also cause Crohn’s disease.

Symptoms of Crohn’s disease

The first signs of Crohn’s disease are usually abdominal pains and diarrhea. Other symptoms include:

  • Abdominal tenderness and swelling in the right lower quadrant (RLQ) of the stomach
  • Blood in the stool
  • Fatigue and fever
  • Loss of appetite
  • Stomach cramps
  • Rectal bleeding
  • Weight loss
  • Fistulas (sores that tunnel through from the GI tract to other organs like the bladder or vagina)
  • Anal fissures.

Other symptoms outside the digestive system can occur like

  • Joint pain
  • Eye inflammation
  • Skin problems.
  • Malabsorption of food which results in nutritional deficiencies

Diagnosis of Crohn’s disease

  • Ileocolonoscopy: Done with an endoscope or flexible probe with a camera at its end inserted through the anus. The pictures taken by the camera reveal the activity of the disease.
  • A stool culture to check for biomarkers that are typical of Crohn’s disease.
  • CT scans can also reveal lesions in the GI tract.
  • CDAI – (Crohn’s disease activity index) and HBI (Harvey Bradshaw Index) also help find the progress of the disease.
  • C reactive protein level is elevated in the blood. CRP is a protein made by the liver and its level goes up in Crohn’s disease. CRP test of blood is also another method of diagnosis.
  • Antibody testing, barium studies, MRE, and biopsy can also be used to diagnose Corhn’s disease.

Irritable Bowel Syndrome (IBS)

This is a functional bowel disorder in which abdominal pain or discomfort is associated with defecation or a change in bowel habits. It affects the large intestine only.

IBS is thought to be associated with the problem in the gut-brain axis. The nervous system regulates the gut activities like intestinal muscle contraction and secretion of digestive enzymes. It also ensures colon movement at an optimal pace. This helps in the absorption of nutrients and water before stool formation. Disturbance and irregular movements hamper this function and lead to abnormal motility of the gut.

 Women are more likely to develop IBS. A history of stress and severe infection of the digestive tract can also cause this syndrome.

IBS has been categorized into the following four types:

  • IBS-d-Diarrhea (loose and watery stools)
  • IBS-c-Constipation (hard and lumpy stools)
  • IBS-m-Mixed; both diarrhea and constipation
  • IBS-U unclassified (it can be of any above types, unspecific)


  • Abnormal gastrointestinal movements.
  • Sensory and motor disorders of the colon
  • A change in the nervous system communication between GI and brain (brain gut interaction).
  • Dietary allergies or food sensitivities
  • Genetics
  • Stress, mental depression, anxiety.
  • Small intestinal bacterial overgrowth (SIBO)


  • Bloating
  • Distensions
  • Recurrent abdominal pain and disordered defecation( diarrhea or constipation) .
  • Mucus in stool
  • Sensation of incomplete bowel movement


  • There is no specific test or blood test to diagnose IBS. It is generally diagnosed based on certain symptoms. Recently there has been an antibody blood test called IBS–Smart. This test measures biomarkers associated with IBS-d and IBS-m.
  • Upper GI tract endoscopy or colonoscopy to check for Inflammatory bowel disease.
  • Gastroenterologists use ROME–IV criteria that create guidelines for diagnosing IBS.
  • Some specific gut microbes are also indicators of IBS. For this, a breath analysis can be done.
  • Blood tests and stool tests may be suggested to check out other health disorders (1).

Key differences

Based on etiology and pathophysiology

Crohn’s disease 

  •  Crohn’s disease exact cause is unclear. Autoimmune involvement, genetic factors, smoking, antibiotics, and prior infection by bacteria or viruses.
  • Crohn’s disease causes intestinal obstruction. It is also called bowel blockage due to the narrowing of thickened areas of the intestine. Ulcers ( open sores) in the mouth, intestine, and anus occur. Anal fissures cause itching and pain. Fistulas ( abnormal passages between the intestinal walls and other organs) are formed. Malnutrition is common due to malabsorption in the ileum if the ileum is affected.


  • IBS is a functional digestive disorder with altered bowel movements and abdominal pain. The main cause is abnormal intestinal motility–too fast causes diarrhea, and too slow causes constipation. 
  •  The pathophysiology of IBS includes visceral afferent hypersensitivity and abnormal GI tract motility. Depression, anxiety, and phobias are also seen. Altered mucosal immune system activation may also occur.

The underlying causes and mechanism

Crohn’s disease

  •   Crohn’s disease is a complex interaction between various environmental factors and genetic predisposition. Changes in NOD2 genes increase the risk of developing Crohn’s disease. Prior exposure to viral and bacterial infection can also be a cause. Psychological stress and smoking can also be an underlying cause.
  •   Crohn’s disease is inflammation of the small intestine and the colon in segments also known as skip lesions. All layers (mucosa, submucosa, muscular layer, serosa) of the GI tract are inflamed anywhere from mouth to anus. Granulosa formation is also seen in one-third of the cases.


  •  IBS can be related to an overly sensitive colon or immune system. Previous gastrointestinal infections can also be an underlying cause. The gut-brain axis can also be a reason for the altered motility of the colon. Stress and certain foods can also be the underlying cause of IBS. It is more common in women. It may be due to chemicals released during reproductive cycles.
  •  IBS is a disorder that affects the colon. Causes abnormal bowel movement with recurrent abdominal pain. Change in form, frequency, or appearance of the stool occurs.

Symptoms of Crohn’s disease and IBS

Crohn’s disease

Symptoms are abdominal pain in the RLQ, diarrhea, weight loss, anemia, and fatigue.  Joint pain and eye inflammation are some of the associated symptoms.


Symptoms are recurrent abdominal pain, bloating, constipation, Flatulence, nausea, diarrhea, and mucus in stools.

Diagnostic test

Crohn’s disease

  • For Crohn’s disease tests like Ileocolonoscopy, biopsy, and CT scan are. Blood tests like antibody tests, C reactive protein tests, and Complete blood count tests are used in diagnosis.


  • For IBS the diagnosis depends on ROME criteria. It is based on clinical grounds radiographic, biochemical, or histological tests are applicable.
  • Recurrent abdominal pain at least three days a month for the past three months. Improvement with defecation. Onset associated with change and form of stool and recent antibiotic use.
  •   Blood tests and stool tests to check out other health problems or coeliac diseases.

 Management for Crohn’s disease and IBS

  •  Crohn’s disease can be managed through medications like corticosteroids, antibiotics, immunosuppressants. Administration of vitamin supplements can also help.
  •   IBS. Intake of more fiber, and probiotics, and limiting caffeine, fatty and spicy foods. Medications can include antispasmodic and antidiarrheals as per the doctor’s advice.

How to live with or manage or cope in day-to-day life

  • Crohn’s disease can be managed by following a disciplined routine. The right amount of exercise, sleep, rest, and proper diet can ease the symptoms. Medications as per the doctor’s advice are to be strictly followed.
  •  IBS can be managed by changing diet (increase of fiber intake). More exercise, proper rest, and sleep are a must. Lastly, Stress management is very essential.

Difference between Crohn’s disease and IBS

Crohn’s disease


Parts affected

Chronic granulomatous disease. The most commonly affected parts are the terminal ileum and colon. Functional disorder of the bowel with no visible structural damage. It is irritable due to visceral hypersensitivity.


Transmural inflammation. The presence of a skip lesion was seen. No inflammation is seen. Irregular motility of the colon. Too fast causes diarrhea as no water can be absorbed. Too slow causes constipation as much water is absorbed during the transit of stool.


Genetic predisposition, autoimmune reaction, stress, certain diet, medications, and smoking seem to cause Crohn’s disease. Brain gut interaction, underlying bacterial infection, overgrowth of bacteria, and food allergies cause IBS. Stress is also a main cause.

Affect on abdominal 

Presence of perianal fistula, and bowel blockage. No associated abnormalities of the GI tract were seen.


Abdominal pain, diarrhea, weight loss, and anemia are seen. Joint pain, loss of appetite, skin and eye problems are seen. Abdominal pain is relieved upon defecation, and mucus in stools. Bloating and diarrhea or constipation happen.

Diagnostic tests

Diagnostic tests of blood, stool culture, ileocolonoscopy, biopsy, and barium tests can confirm Crohn’s disease. Diagnosis depends on ROME–IV criteria. Recurrent abdominal pain at least three days a month for the past three months. Improvement with defecation. Onset associated with change and form of stool and recent antibiotic use. Stool and blood tests can be done to rule out other health complications.


Immunosuppressants, corticosteroids, antibiotics, and vitamin supplements can be used to control the symptoms. Surgery can be performed depending on the severity of the symptoms. Medications can include antispasmodic and antidiarrheals.


Suitable lifestyle modifications (exercises, destress) and changes in diet can improve the conditions. Intake of probiotics, adequate water intake, and no smoking help in management of this disease. Dietary modifications like excluding lactose, and gluten help soothe IBS. Increased intake of fiber helps IBS patients. Mental therapy and stress management are also recommended.


1. How do I know if it is IBS or Crohn’s?

IBS causes pain in the lower left side of the abdomen. Crohn’s disease causes pain in the lower right quadrant of the abdomen. A colonoscopy reveals no visible damage to the GI tract in IBS. Crohn’s disease shows skip lesions, granulosa formation, and inflammation of the GI tract.

2. How can you tell the difference between IBS and IBD?

In IBS improper functioning of the bowel takes place with no visible structural damage to the GI tract. Sensory nerve endings in the bowel are irritated and give the sensation of pain. It can cause either constipation diarrhea or both.

In IBD the bowel is inflamed causing damage to the GI tract. There is blood in the stool.

3. What is the difference between IBD and Crohn’s?

Crohn’s disease is transmural and affects any part of the GI tract.

IBS infects mainly the colon and rectum. Mucosa and submucosa layers of the GI tract are affected.

4. What is the main difference between Crohn’s and colitis?

Crohn’s disease causes inflammation and damage to the terminal ileum and the whole of the colon.

Colitis is the acute inflammation of the colon.


The difference between Crohn’s disease and IBS is that the former is a type of IBD. The other form is ulcerative colitis (UC). IBS is a functional disorder of bowel movement. It is irritable due to hypersensitive nerve endings in the bowel.

Written By: Ahana Mitra