Crohn’s disease

What is Crohn's disease?

Crohn's disease is a chronic autoimmune inflammatory bowel disease characterised by transmural inflammation, meaning it affects all layers of the bowel wall rather than just the inner lining. It can occur anywhere along the gastrointestinal tract. It is one of the two main forms of inflammatory bowel disease (IBD), distinct from ulcerative colitis which is confined to the colon's inner lining. For an overview of IBD as a whole, see our IBD page.

The most commonly affected regions are the terminal ileum and the colon, though Crohn's can involve several separate segments of bowel at once, a pattern known as skip lesions. This patchy, full-thickness nature is what distinguishes it from ulcerative colitis, and it has real implications for complications and management.

Crohn's disease is classified by its behavioural phenotype:

• Inflammatory (non-stricturing, non-penetrating) active mucosal inflammation without complications. The most common phenotype at diagnosis, with the highest potential for response to medical treatment.

• Stricturing chronic full-thickness inflammation causes progressive scarring and thickening of the bowel wall, leading to narrowing of the intestine that can cause partial or complete obstruction.

• Penetrating transmural inflammation penetrates through the full bowel wall to create fistulae (abnormal connections between the bowel and nearby structures including the skin, bladder, vagina, or other bowel loops) and abscesses.

Disease behaviour tends to progress over time, with many patients moving from inflammatory toward stricturing or penetrating phenotype. Early effective treatment significantly reduces the risk of this progression.

Symptoms of Crohn's disease

Crohn's disease symptoms depend on which part of the gut is affected and fluctuate between active flares and remission.

Common intestinal symptoms:

• Abdominal pain and cramping: often localized in the lower right side.

• Bowel changes: chronic diarrhea (sometimes with blood or mucus), nausea, and vomiting from blockages.

• Systemic effects: unexplained weight loss, fever, loss of appetite, and persistent fatigue from anemia or inflammation.

• Perianal issues: painful fissures, skin tags, abscesses, or fistulas around the anus.

Extraintestinal symptoms (affecting up to 40% of patients):

• Joints, eyes and skin: joint pain, eye inflammation (uveitis), and painful skin rashes or ulcers (erythema nodosum).

• Liver: inflammation and scarring of the bile ducts (primary sclerosing cholangitis).

What causes Crohn's disease?

Crohn's develops when an overactive immune system reacts inappropriately to normal gut bacteria, in people who are genetically susceptible. Key contributing factors include:

• Immune and genetic vulnerability: abnormal immune responses drive deep intestinal inflammation, with over 200 associated genes, most notably NOD2 mutations, which impair how the body recognizes bacteria.

• Microbiome and environment: reduced gut bacteria diversity, Western diets, childhood antibiotic use, and past stomach infections can alter the gut environment and trigger disease onset.

• Lifestyle and stress: smoking significantly increases the risk of Crohn's and worsens flares, while psychological stress weakens the gut barrier and disrupts immune function.

How is Crohn's disease detected?

Crohn's disease is detected through a combination of abdominal MRI, blood tests, and ultimately endoscopic assessment with biopsy for definitive diagnosis.

Abdominal MRI and MR enterography Elfcare uses targeted MR enterography (MRE) as the leading radiation-free imaging tool for assessing Crohn's disease, providing detailed imaging of the small bowel alongside standard abdominal coverage on full-body scans. MRE directly visualizes bowel wall thickening, active inflammation, and the classic "comb sign" of increased mesenteric blood flow, while effortlessly spotting skip lesions, strictures, and penetrating complications like fistulas or abscesses to deliver a complete picture of your gut health.

Blood tests assess the inflammatory burden, nutritional consequences, and systemic impact of Crohn's disease. Relevant markers in Elfcare's panel include:

• CRPprimary inflammation marker that tracks disease activity and guides treatment.

• Hemoglobin, MCV and ferritin detects iron deficiency anemia caused by chronic bleeding or poor absorption.

• Vitamin B12 flags absorption issues specifically linked to inflammation in the lower small intestine.

• Vitamin Didentifies common deficiencies resulting from malabsorption and reduced sun exposure.

• Albumin indicates active inflammation and overall nutritional depletion.

• Full blood count highlights active infections via elevated white cells or medication side effects via lower counts.

• Liver enzymes (ALT, AST, GGT, ALP) checks for liver complications or medication toxicity.

• tTG-IgA screens for celiac disease, which mirrors Crohn's symptoms.

• Homocysteine reveals elevated cardiovascular risk driven by B12 and folate malabsorption.

• Uric acid tracks increased cell turnover during active flares or medication responses.

Note: Faecal calprotectin is the most sensitive non-invasive stool test for gut inflammation. While not in the standard blood panel, it is prioritized during specialist follow-up if Crohn's is suspected.

Why early detection matters

Each inadequately treated inflammatory episode adds to cumulative, irreversible bowel damage. Central to modern Crohn's management is the idea of a "therapeutic window": the period of early disease before stricturing or penetrating complications develop. Biological therapy started before that damage accumulates can achieve mucosal healing, prevent strictures forming, and dramatically cut the lifetime risk of surgery. The same treatment started after strictures or fistulae have already developed can still ease symptoms, but it can't reverse the structural damage that's already there. Catching Crohn's at the inflammatory stage, through MRI and blood testing, before it progresses to stricturing or penetrating disease, is the single biggest opportunity to change its course.

How Elfcare can help

Elfcare's abdominal MRI images the small and large bowel directly, identifying the transmural inflammation, skip lesions, strictures, and fistulae characteristic of Crohn's disease. These are structural findings that provide the clinical basis for urgent specialist referral and starting treatment. MR enterography provides particularly detailed small bowel assessment when Crohn's is suspected or confirmed.

Our blood panel covers CRP, haemoglobin, ferritin, B12, vitamin D, albumin, and liver function, providing a comprehensive picture of inflammatory activity, nutritional status, and systemic consequences.

If our MRI or blood tests identify findings consistent with Crohn's disease, we take care of further diagnostics or refer you to the appropriate specialist.