Crohn’s disease is a chronic, long term condition characterised by inflammation that can occur anywhere along the digestive tract. It is classified as an inflammatory bowel disease and is distinct from functional disorders like irritable bowel syndrome because it involves physical damage and inflammation of the gut wall. While it can affect individuals of any age, it is most frequently diagnosed in teenagers and young adults. Crohn’s disease follows a relapsing and remitting course, meaning patients experience flare ups of active symptoms followed by periods of remission where they feel relatively well. Although there is currently no cure, modern medical treatments are highly effective at controlling inflammation and preventing serious complications.
What we will discuss in this article
- The primary areas of the digestive tract affected by the condition
- Common symptoms including diarrhoea, pain, and systemic fatigue
- The role of the immune system and genetics in triggering inflammation
- Long term complications such as strictures, fistulas, and abscesses
- The diagnostic process including blood tests, stool samples, and endoscopy
- Emergency guidance for life threatening symptoms
- Strategies for managing the condition and achieving long term remission
Where does Crohn’s disease occur?
Unlike ulcerative colitis, which is limited to the colon and rectum, Crohn’s disease can affect any part of the gastrointestinal system from the mouth to the anus.
The inflammation in Crohn’s disease is often patchy. This means that a person may have sections of severely inflamed tissue right next to sections of completely healthy bowel. These healthy areas are known as skip lesions. The most common site for inflammation to begin is the terminal ileum, which is the final section of the small intestine, but the large intestine is also frequently involved. Furthermore, the inflammation in Crohn’s disease is transmural, meaning it can penetrate through all layers of the bowel wall rather than just the innermost lining.
Common symptoms and signs
The symptoms of Crohn’s disease vary depending on which part of the gut is inflamed and how severe the inflammation has become.
Digestive symptoms
The most frequent symptom is persistent diarrhoea, which may sometimes contain blood, mucus, or pus. Abdominal pain and cramping are also very common, often felt in the lower right side of the stomach after eating. Some individuals may experience a frequent urge to have a bowel movement even when the bowel is empty, a sensation known as tenesmus.
Systemic and extra intestinal symptoms
Because it is an inflammatory condition, Crohn’s disease often affects the whole body. Many people suffer from extreme tiredness and fatigue that does not improve with rest. Unintended weight loss and a loss of appetite are also common indicators. Some patients develop symptoms outside of the gut, such as mouth ulcers, painful red eyes, skin rashes, or swollen and aching joints.
Causes and risk factors
The exact cause of Crohn’s disease is not yet fully understood, but it is widely believed to be the result of a combination of factors.
The leading theory is that the immune system mistakenly attacks healthy bacteria in the gut, leading to chronic inflammation. Genetics also play a significant role: about three in twenty people with the condition have a close relative who also has it. Environmental triggers are another important factor. Smoking is a well-documented risk factor that significantly increases the chance of developing the disease and makes flare ups more severe. Other possible triggers include a diet high in processed foods, recent gut infections, or an imbalance in the natural bacteria living in the digestive system.
Complications of chronic inflammation
If left untreated, the deep inflammation caused by Crohn’s disease can lead to structural damage within the bowel.
Strictures and £obstructions
Repeated cycles of inflammation and healing can cause scar tissue to build up, leading to a narrowing of the bowel called a stricture. This can make it difficult for food to pass through, potentially leading to a partial or complete bowel obstruction.
Fistulas and abscesses
When ulcers become deep enough to break through the bowel wall, they can create abnormal tunnels called fistulas. These tunnels can connect the bowel to other organs, such as the bladder, or even to the surface of the skin. If an area of infection becomes trapped, a painful pocket of pus called an abscess may form, often requiring drainage or antibiotics.
How is Crohn’s disease diagnosed?
There is no single test that can definitively diagnose Crohn’s disease. Instead, doctors use a combination of investigations to confirm the condition.
The diagnostic process typically begins with blood tests to check for markers of inflammation and anaemia. A stool sample is often requested to measure faecal calprotectin, a protein that indicates active gut inflammation. To see the inflammation directly, a specialist will perform an endoscopy or colonoscopy, where a camera is used to inspect the lining of the gut and take small tissue samples called biopsies. In some cases, imaging scans such as an MRI or CT scan are used to check the small intestine.
Emergency guidance
While most symptoms can be managed through regular clinical care, certain situations require urgent medical intervention.
Call 999 or go to the nearest emergency department immediately if you experience:
- Severe or worsening abdominal pain that makes it difficult to move.
- Signs of a bowel obstruction, such as an inability to pass gas or stool combined with vomiting and a swollen tummy.
- Heavy or non-stop bleeding from the bottom.
- A high fever combined with severe shaking or chills.
- Signs of a perforated bowel, which causes sudden and intense abdominal pain.
To summarise
Crohn’s disease is a lifelong inflammatory condition that can affect any part of the digestive tract in a patchy, transmural fashion. It is driven by an abnormal immune response and is influenced by genetics and lifestyle factors like smoking. While symptoms like diarrhoea, pain, and fatigue can be debilitating, early diagnosis through clinical testing and endoscopy is key to effective management. By working closely with a specialist team and following a personalised treatment plan, most individuals can achieve long periods of remission and maintain a good quality of life.
Can I have Crohn’s disease and irritable bowel syndrome at the same time?
While you cannot have both conditions in the same part of the gut, some people with Crohn’s disease also experience IBS like symptoms even when their inflammation is under control.
Is Crohn’s disease caused by stress?
Stress does not cause Crohn’s disease, but it is a major factor that can trigger a flare up or make existing symptoms feel much worse.
Will I definitely need surgery?
Not everyone with Crohn’s disease needs surgery. Many people manage their condition effectively with medications, though surgery may be required if complications like strictures or fistulas develop.
Can Crohn’s disease be cured by a special diet?
There is no specific diet that can cure Crohn’s disease. However, identifying your personal food triggers and eating a balanced diet can help manage symptoms during a flare.
How is Crohn’s different from ulcerative colitis?
The main difference is that Crohn’s can affect the entire digestive tract and the full thickness of the bowel wall, while ulcerative colitis only affects the colon and the innermost lining.
Does smoking really make Crohn’s worse?
Yes, smokers with Crohn’s disease tend to have more frequent flare ups, more severe symptoms, and a higher likelihood of needing surgery compared to non-smokers.
Can children have Crohn’s disease?
Yes, it can be diagnosed at any age. In children, it often presents as a failure to grow as expected or a delay in the onset of puberty.
Authority Snapshot
This article was reviewed by Dr. Stefan Petrov, a physician with an MBBS and extensive experience in general medicine, surgery, and emergency care. Dr. Petrov has worked in hospital wards and intensive care units, performing diagnostic procedures for gastrointestinal conditions. He specialises in medical education and ensuring that patients understand the clinical pathways for managing chronic inflammatory disorders through evidence based dietary and lifestyle modifications.
