Overview of Crohn's Disease

Crohn's disease is a chronic and recurrent inflammatory bowel disease primarily affecting the gastrointestinal tract, but it can involve any part from the mouth to the anus. Characterized by chronic inflammation of the intestinal mucosa, it often leads to symptoms such as abdominal pain, diarrhea, and intestinal obstruction, which may require surgical intervention in severe cases. In recent years, the global incidence of Crohn's disease has continued to rise, especially among young populations in industrialized countries.

The diagnosis and treatment of Crohn's disease pose challenges due to its diverse symptoms and potential confusion with other gastrointestinal diseases. Patients often require long-term follow-up by a multidisciplinary medical team, including gastroenterologists, nutritionists, and psychiatrists. Recent research indicates that the interaction between genetic susceptibility, environmental triggers, and gut microbiota imbalance is a key mechanism in the development of this disease.

Etiology and Risk Factors

Genetic Predisposition and Gene Variations

Studies show that about 20% of patients have a family history, and abnormalities in specific genes such as NOD2 and ATG16L1 increase the risk of developing the disease. These genes are responsible for regulating intestinal immune responses and bacterial clearance; their defects lead to impaired intestinal barrier function. Twin studies further confirm that the concordance rate in monozygotic twins can be as high as 50%, highlighting the crucial role of genetics in the disease mechanism.

• Polymorphisms in specific chromosomal regions are associated with inflammatory response regulation
• Gene combinations determine individual sensitivity to environmental triggers
• Patients with a family history tend to develop the disease at an earlier age

Environmental and External Triggers

Modern lifestyles and environmental exposures are believed to be key factors in the rising incidence. Urbanized areas have a threefold higher proportion of patients compared to rural areas, suggesting that reduced microbial exposure in city environments may affect immune system development. The use of antibiotics, high intake of processed foods, tobacco use, and hormonal stress have all been proven to induce abnormal activation of the intestinal immune system.

Tar components in tobacco can directly damage the tight junctions between intestinal epithelial cells, leading to compromised barrier function. Long-term smokers have a 2.5 times higher risk of developing the disease, and the severity of symptoms correlates positively with smoking duration.

Symptoms

The symptoms of Crohn's disease vary depending on the site and severity of inflammation, commonly including:

• Gastrointestinal symptoms: Abdominal pain often localized to the right lower abdomen, possibly accompanied by intermittent diarrhea, with 3-5 watery stools containing mucus or blood daily
• Systemic symptoms: Chronic inflammation leading to weight loss, fever, fatigue, and anemia; some patients may experience joint pain or skin erythema as extraintestinal manifestations
• Structural abnormalities in the intestines: Chronic inflammation may result in fistulas, strictures, or abscesses, with a stricture occurrence rate reaching 40% in patients with over five years of disease duration

Variability of Symptoms

Approximately 30% of patients initially present with mild symptoms that may be mistaken for common gastrointestinal discomfort. The disease can have cyclical phases of remission and exacerbation, with the severity of symptoms during flare-ups directly related to the extent of intestinal involvement. Pediatric patients may experience growth retardation due to impaired intestinal development, which is a critical clinical emergency.

Diagnosis

The diagnostic process involves ruling out other intestinal diseases such as ulcerative colitis, with common examinations including:

• Endoscopy: Colonoscopy and upper gastrointestinal endoscopy to observe the degree of mucosal inflammation and obtain biopsies to confirm non-caseating granulomas and other lesions
• Imaging studies: Computed Tomography Enterography (CTE) or Magnetic Resonance Enterography (MRE) to evaluate full-thickness intestinal inflammation and structural abnormalities
• Biomarkers: Elevated serum C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) indicate active inflammation but are non-specific markers

Diagnostic Criteria

Currently, diagnosis relies on exclusion, requiring evidence of transmural inflammation (the "Swiss cheese" pattern) and non-caseating granulomas confirmed by histopathology and imaging. The diagnostic process generally includes:

1. Initial symptom assessment and family history analysis
2. Blood and stool tests to screen for infectious enteritis
3. Pathological evidence from endoscopic biopsies
4. Imaging assessment of structural abnormalities

Treatment Options

The goal of treatment is to control inflammation, maintain remission, repair intestinal damage, and improve quality of life. Standard treatment options include:

• Anti-inflammatory drugs: 5-Aminosalicylic acid (5-ASA) agents for mild inflammation, with limited efficacy for deep transmural inflammation
• Immunomodulators: Azathioprine and methotrexate to suppress abnormal immune activation, with an onset time of approximately 6-8 weeks
• Biologic agents: Anti-TNF-α monoclonal antibodies (e.g., infliximab) that rapidly inhibit key inflammatory cytokines; screening for tuberculosis infection is required before use

Surgical and Alternative Therapies

About 70% of patients require intestinal resection during their disease course, but postoperative recurrence rates can reach 50%. Emerging therapies include microbiota restoration, stem cell therapy, and personalized pharmacogenomics. Nutritional support, such as elemental diets, can significantly alleviate symptoms in some patients.

Long-term Management Strategies

Patients need regular monitoring of inflammatory markers and intestinal structural changes, with treatment plans adjusted dynamically based on disease stage. Establishing psychosocial support systems can improve treatment adherence and quality of life; approximately 40% of patients experience anxiety or depression that requires concurrent management.

Prevention

There is currently no evidence that Crohn's disease can be completely prevented, but the following measures may reduce the risk of flare-ups:

• Smoking cessation can reduce flare-up frequency by 30% and improve treatment response
• Maintaining a normal body mass index (BMI); obesity shortens the interval between flare-ups by 25%
• Regular exercise can modulate gut microbiota composition and reduce circulating inflammatory cytokine IL-6 levels

Dietary Management Strategies

A low FODMAP diet can alleviate bloating and diarrhea but should be implemented under the supervision of a nutritionist to prevent nutritional deficiencies. Some patients are sensitive to dairy products or certain food additives; maintaining a food diary can help identify triggers. Probiotic supplementation may improve gut microbiota diversity but should be based on strains validated through clinical trials.

When Should You See a Doctor?

Seek medical attention immediately if you experience:

• Unintentional weight loss exceeding 5% within one month
• Persistent abdominal pain with blood in stool or vomiting blood
• Fever over 38.5°C lasting more than 48 hours
• Perianal ulcers or abscesses
• Growth retardation in pediatric patients

For patients under regular outpatient follow-up, consult a doctor if:

• Biologic therapy efficacy diminishes within three months
• New extraintestinal manifestations such as arthritis or skin nodules appear
• Blood tests show elevated acute-phase proteins

Early medical intervention can prevent complications such as intestinal strictures or perforation. It is recommended to use Crohn's disease-specific assessment tools (e.g., CDAI index) to quantify symptom severity.

 

Frequently Asked Questions

Do people with Crohn's disease need to completely avoid certain types of foods?

Patients should adjust their diet based on individual symptoms, but there is no universal list of foods to avoid. Generally, high-fiber, spicy foods, and dairy products are recommended to be limited, but specific restrictions should be evaluated by a physician. Using elimination diets or monitoring with a nutritionist can help identify personal triggers to reduce intestinal irritation.

What is the main role of biologic agents in Crohn's disease treatment?

Biologic agents primarily target specific immune molecules (such as TNF-α), suppressing excessive inflammatory responses to control the disease. Compared to traditional immunosuppressants, they are more targeted and can rapidly improve symptoms, but require regular monitoring for infection risks and potential side effects.

Does long-term stress worsen the frequency of Crohn's disease flares?

Stress may trigger or exacerbate symptoms because stress hormones influence intestinal immune function. Managing stress through mindfulness meditation, regular exercise, or psychological counseling can help reduce the risk of acute flare-ups.

Should Crohn's disease treatment be adjusted during pregnancy?

Treatment plans should be tailored to the pregnancy, as some medications may affect fetal development. Physicians typically prefer to choose safer drugs (such as certain biologics) and closely monitor intestinal activity and pregnancy progress to balance disease control with fetal safety.

What are the recent findings regarding the relationship between gut microbiota imbalance and Crohn's disease?

Recent studies suggest that a reduction in beneficial bacteria (such as Faecalibacterium prausnitzii) may worsen inflammation. Probiotic supplementation or fecal microbiota transplantation is currently in clinical trials, but should be used under medical supervision to avoid infection risks from self-treatment.