Inflammatory Bowel Disease

Gastroenterology (12%) Core Clinical Conditions

Jump to content

Definition Aetiology Pathophysiology Sign and Symptoms Investigations Management

Inflammatory Bowel Disease (IBD) is a chronic disorder that affects the digestive tract, causing inflammation and damage primarily within the intestines. It encompasses two main conditions: Crohn's disease and ulcerative colitis. While they share some similarities, they also possess distinct characteristics that differentiate them from one another.

1. Crohn's Disease: This form of IBD can affect any part of the digestive tract, from the mouth to the anus. However, it most commonly occurs in the small intestine and the beginning of the large intestine. The inflammation caused by Crohn's disease extends through all the layers of the intestinal walls, leading to ulcers, deep tissue damage, and potential complications such as abscesses or fistulas. Symptoms can vary in severity and commonly include diarrhoea, abdominal pain, weight loss, fatigue, and malnutrition.

2. Ulcerative Colitis: Unlike Crohn's disease, ulcerative colitis is limited to the large intestine and rectum. The inflammation starts in the rectum and then spreads continuously to the colon. The innermost lining of the colon develops ulcers and becomes inflamed, leading to symptoms like bloody diarrhoea, abdominal cramping, urgency to have a bowel movement, and a persistent or recurring need to empty the bowels. In severe cases, individuals with ulcerative colitis may experience weight loss, fever, and dehydration.

Both Crohn's disease and ulcerative colitis are considered autoimmune disorders, meaning that the body's immune system mistakenly attacks the gastrointestinal tract, causing chronic inflammation.

Genetic Factors:
There is a significant genetic component to the development of IBD. Studies have shown that individuals with a family history of IBD have a higher risk of developing the disease themselves. Mutations in specific genes, such as the NOD2/CARD15 gene, have been implicated in the pathogenesis of Crohn's disease – a form of IBD. These genetic factors contribute to a defective immune response, impaired intestinal barrier function, and abnormal handling of gut microbiota.
Environmental Factors:
Environmental factors play a crucial role in triggering and influencing the course of IBD. Smoking, for instance, has been consistently identified as a significant risk factor for Crohn's disease. Other environmental factors, including diet, infections, stress, and the use of certain medications, can also contribute to the development of IBD. Dietary factors, especially the consumption of high-fat, high-sugar, and processed foods, are believed to have a pro-inflammatory effect, potentially exacerbating the condition. Exposure to certain pathogens, such as bacteria or viruses, may trigger an abnormal immune response in susceptible individuals, leading to chronic inflammation in the gut.
Immunological Factors:
The immune system plays a pivotal role in the pathogenesis of IBD. It is believed that an aberrant immune response is triggered by an unknown environmental trigger in genetically susceptible individuals. The intestinal immune system, responsible for distinguishing between harmful bacteria and beneficial microorganisms, becomes dysregulated and reacts excessively, triggering inflammation. Dysfunction in immune cells, particularly T-cells and dendritic cells in the gut, leads to the excessive production of pro-inflammatory cytokines. This immune dysregulation results in the infiltration of immune cells into the intestinal wall, causing chronic inflammation and tissue damage.
Microbiota Dysbiosis:
The gut microbiota, the diverse community of microorganisms residing in the digestive tract, also plays a role in the aetiology of IBD. It is thought that an imbalance or dysbiosis in the gut microbial composition can contribute to the development and progression of the disease. The disrupted microbial ecosystem may lack beneficial bacteria, leading to the overgrowth of harmful or pathogenic species. This dysbiosis can trigger an inappropriate immune response and affect the integrity of the intestinal barrier, perpetuating chronic inflammation.

Genetic Predisposition: Multiple genes have been implicated in the development of IBD, suggesting a genetic predisposition. Variations in genes related to the immune system, such as the NOD2/CARD15 gene, have been associated with an increased risk of developing CD. However, genetic susceptibility alone is not sufficient for disease development, as environmental factors play a significant role.
Immune Dysfunction: Dysregulation of the immune system is considered a central feature in the pathophysiology of IBD. There is evidence of an overly aggressive immune response to normal gut bacteria in individuals with IBD. In a genetically susceptible individual, exposure to environmental triggers (e.g., certain bacteria, viruses, or food antigens) leads to an uncontrolled immune response within the GI tract.
Inflammation and Tissue Damage: The initial trigger activates immune cells, such as T lymphocytes, macrophages, and dendritic cells, within the intestinal lining. These cells release pro-inflammatory cytokines (e.g., tumour necrosis factor-alpha, interleukin-1, and interleukin-6), which promote recruitment of additional immune cells and perpetuate the inflammatory process.
Intestinal Barrier Dysfunction: In IBD, there is impaired intestinal barrier function, allowing for increased permeability of the gut lining to luminal contents. This breach in the barrier allows antigens, bacteria, and other harmful substances to penetrate the intestinal wall, setting the stage for an amplified immune response.
Alteration in Gut Microbiota: The gut microbiota, comprising millions of bacteria, fungi, and viruses, plays a crucial role in maintaining intestinal homeostasis. In individuals with IBD, there is an imbalance in the composition of the gut microbiota, known as dysbiosis. Dysbiosis can further promote inflammation and disrupt the delicate balance between the immune system and the gut microbiota.
Chronicity and Remission: The chronic nature of IBD arises from a dysregulated inflammatory response, which persists even after the initial trigger has been resolved. This chronic inflammation can lead to tissue damage, ulceration, and thickening of the intestinal walls. Periods of remission may occur when the inflammation subsides, but relapses are common, triggered by certain factors such as stress, diet, or microbial changes.

1. Abdominal pain and cramping: One of the most recognizable symptoms of IBD is abdominal pain, which can range from mild discomfort to severe cramping. The pain is often located in the lower right or lower left quadrant of the abdomen.
2. Persistent diarrhoea: Frequent and chronic diarrhoea is another characteristic symptom of IBD. It may involve loose, watery stools and can be accompanied by urgency or a feeling of incomplete evacuation.
3. Rectal bleeding: Inflammatory bowel disease can cause inflammation and ulcers in the intestines, leading to rectal bleeding. Blood may be present in the stool or may be seen on toilet paper after wiping.
4. Unexplained weight loss: As IBD affects the body's ability to absorb nutrients, individuals with the condition may experience unintentional weight loss. This can be attributed to decreased appetite, malabsorption, and increased calorie expenditure due to chronic inflammation.
5. Fatigue and weakness: IBD can cause chronic inflammation, which can lead to general fatigue and a sense of weakness. The body's immune response and the ongoing inflammation may contribute to these feelings of fatigue.
6. Fever: Many individuals with IBD may experience low-grade fevers that come and go. These fevers are often related to the ongoing inflammation present in the gastrointestinal tract.
7. Loss of appetite: Inflammatory bowel disease can affect the normal functioning of the digestive system, leading to a loss of appetite. This can result in weight loss and overall nutritional deficiencies if not managed properly.
8. Joint pain: IBD can cause inflammation not only in the gut but also in other parts of the body, including the joints. Joint pain and swelling, similar to arthritis, can be common in individuals with IBD.
9. Skin problems: Certain skin conditions, such as erythema nodosum and pyoderma gangrenosum, can be associated with inflammatory bowel disease. These conditions cause painful red nodules or ulcers on the skin.
10. Mouth sores: Some individuals with IBD may develop mouth ulcers or sores, particularly in the lining of the inner cheeks and lips. These sores can be painful and make eating and talking uncomfortable.

Clinical Assessment:

The first step in diagnosing IBD involves a thorough clinical assessment, including a detailed medical history and physical examination. Key symptoms suggestive of IBD may include persistent diarrhoea, abdominal pain, rectal bleeding, unexplained weight loss, fatigue, and changes in bowel habits. The duration, frequency, and severity of these symptoms are essential in differentiating between Crohn's disease and ulcerative colitis.

Laboratory Tests:

Laboratory tests play a vital role in supporting the diagnosis of IBD and ruling out other possible causes of gastrointestinal symptoms. Common blood tests include:

1. Full Blood Count (FBC): Evaluation of red blood cells, white blood cells, and platelets can identify anaemia, infection, and inflammation.

2. C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR): Increased levels of these markers can indicate inflammation in the body, aiding in the diagnosis and monitoring of disease activity.

3. Stool Analysis: Examination of stool for blood, white blood cells, and infectious agents can exclude infections or colitis. This includes a faecal calprotectin test or faecal immunochemical test (FIT).

Imaging Studies:

Various imaging techniques can provide valuable information in the diagnosis and assessment of IBD. These may include:

1. Endoscopy and Colonoscopy: These procedures involve a flexible tube with a light and camera being inserted through the mouth or rectum, allowing visualisation of the digestive tract's inner lining. Biopsies can be obtained during these procedures for further analysis.

2. Computed Tomography (CT) Scan: CT scans can identify complications such as fistulas, abscesses, or bowel obstruction that may occur in Crohn's disease.

3. Magnetic Resonance Imaging (MRI): MRIs are useful for visualising the intestine and surrounding structures, particularly in evaluating perianal disease or for those who cannot tolerate a CT scan or undergo radiation.

1. Medication: Medications play a crucial role in managing IBD symptoms and reducing inflammation. Medications such as aminosalicylates, corticosteroids, immunomodulators, or biologics. These medications aim to suppress the inflammatory response, control symptoms, and prevent flare-ups.

2. Diet and Nutrition: A well-balanced and individualised diet is essential for managing IBD. While there isn't a specific diet that works for everyone, certain dietary modifications can be beneficial. A low-residue or low-fibre diet may be recommended during flare-ups to reduce bowel movements and relieve symptoms. Additionally, some individuals find that avoiding trigger foods, such as high-fat foods, caffeine, spicy foods, or alcohol, helps in managing symptoms. Registered dietitians can provide personalised guidance on dietary adjustments.

3. Surgery.

Jump to other topics below: