Overview

Inflammatory Bowel Disease (IBD) is a chronic condition that affects the gastrointestinal tract characterized by the dysregulation of the immune system.IBD is primarily classified into two types: ulcerative colitis (UC) and Crohn's disease (CD). However, there is a third classification called indeterminate colitis which does not meet the criteria for being classified as ulcerative colitis or Crohn's disease.¹ UC and CD are more prevalent in Europe and North America than in other regions. For example, in Europe, there are about 505 cases of ulcerative colitis per 100,000 people and about 322 cases of Crohn's disease per 100,000 people.²

IBD significantly impacts patients' quality of life, mental health, and work productivity, placing a considerable burden on healthcare systems. In order to avoid complications from this disease, an accurate diagnosis and appropriate treatment are required. About 70% of cases are diagnosed via colonoscopy, while the remainder may require imaging techniques like CT, MRI, or capsule endoscopy.¹ To understand the disease, we will examine its causes, associated factors, and, finally, its symptoms.

Causes

The cause of IBD is unclear, but a mix of factors has been shown to have an effect. Different factors, such as inadequate immune response, external environment, intestinal microbial flora, and individual genetic susceptibility, are still being studied to explain the pathogenesis of this disease.⁴

Genetics

Each gene contains different versions, known as variants. More than 200 genetic variants have been associated with IBD.⁵ When someone develops this disease, they often have a combination of these genetic variants. However, a single genetic variant may be enough to cause the disease in some cases, although this is not very common. The risk of suffering from this disease is greater in those who have a first-degree relative with inflammatory bowel disease, and this risk increases even more in relatives of patients who developed the disease as children. Additionally, the likelihood of inheriting inflammatory bowel disease varies depending on the type of disease. For example, approximately 30% of Crohn's disease cases can be attributed to genetics. At the same time, this percentage is around 15% for ulcerative colitis.⁶

Environment

Several environmental factors have been identified as potential risk factors for IBD, including (7,8):

• Diet
• Smoking (active and passive)
• Varicella (chicken pox) infection
• Social stress
• Psychological element
• Geography
• Low vitamin D
• Air pollution
• Certain medications, such as antibiotics (especially metronidazole and fluoroquinolones) and oral contraceptives⁷
• Protective factors^{7, 9}
• Breastfeeding
• Appendectomy
• Rotavirus vaccine

Microbial factors

The intestinal microbiota is like a community of microorganisms, mainly bacteria, that live in our intestines. These microorganisms begin to colonise our intestines from the moment we are born. However, this community can change over time due to our diet, our immune system, and the microorganisms around us in the environment. Changing this community may be linked to inflammatory bowel diseases. People with these diseases have fewer different microorganisms and lack bacteria that keep our intestines healthy.¹⁰

Immunological factors

Inflammatory Bowel Disease (IBD) involves a complex interplay of our body's defence system, the immune system, which goes awry. Imagine the lining of your intestines like a protective shield. In IBD, this shield gets damaged, making it vulnerable to inflammation. This inflammation is like an overreaction of your body's defences triggered by the bacteria in your gut. It leads to an influx of immune cells, such as T cells, B cells, and others, into the intestinal wall. Unfortunately, the system that usually puts the brakes on this inflammation doesn't work correctly in IBD, allowing it to spiral out of control. These activated immune cells then release powerful substances called cytokines, which further fuel the inflammation, causing the symptoms we associate with IBD, like abdominal pain and diarrhoea. So, in simpler terms, in IBD, the immune system mistakenly attacks the intestines, leading to inflammation and all the discomfort that comes with it.¹¹

Types of inflammatory bowel disease

Chronic and inflammatory diseases usually appear between 20 and 40 years of age and affect men more. It has also been noted that the incidence varies by ethnic group, being more common in Jews and non-Jewish whites. Currently, it is known that genetic predisposition plays an essential role in these diseases, especially in Crohn's disease compared to ulcerative colitis. Although both are considered chronic inflammatory diseases, they have different symptoms, different prognoses, and require different treatments.¹²

Ulcerative colitis

In ulcerative colitis, damage occurs in the mucosa of the rectum. It can extend to part or all of the colon and is more common in the rectum and sigmoid rectum.¹²

The degree of inflammation will depend on the person and can range from mild inflammation to more severe cases with bleeding, inflammation, and ulcers. In some patients with long-standing disease, inflammatory polyps appear. Patients with many years of disease will also present atrophy, which means a decrease in the size of the colon and lumen.¹²

Complications

Different complications can occur in the active form, such as massive bleeding, toxic megacolon, perforation and stenosis.¹² One of the severe complications of ulcerative colitis is toxic colitis or megacolon, in which the mucosa presents ulcers and is severely thickened. When it is not treated promptly, it can become perforated.¹²

Crohn's disease

Crohn's disease is a long-lasting gut illness. It causes inflamed intestines, with periods of it worsening and then worsening. This is linked to how the body's defence system reacts, as swelling is a big part.¹³

Compared to ulcerative colitis, Crohn's disease occurs throughout the digestive tract, that is, from mouth to anus; However, 75% will present the disease in the small intestine, and 90% will show it in the terminal ileum.³ Another characteristic of Crohn's disease is that it does not generally involve the rectum.¹³

Compared to ulcerative colitis, Crohn's disease affects all layers of the digestive tract. The inflammation can generate small superficial ulcers or ulcers until stellate ulcerations fuse longitudinally and transversally.¹² The inflammation is characterized by being focal and generating fistulas, fibrosis and bowel obstruction. Furthermore, the walls of the intestine thicken, decreasing the lumen and intestinal obstructions.¹²

Complications

Complications of Crohn's disease include toxic megacolon, perforation, abscess, intestinal obstruction, massive bleeding, malabsorption and severe perianal disease.¹²

Symptoms

Inflammatory bowel disease could result in gastrointestinal and extraintestinal symptoms. Both types of IBD have an overlap in symptoms, making the diagnosis complicated in some cases; these are classified as non-specific colitis.

Crohn's disease and ulcerative colitis experience similar symptoms:

• Nausea
• Vomiting
• Abdominal pain
• Diarrhea
• Pain or discomfort in the rectum
• Blood mixed with mucus in the stools
• Urgency

More general symptoms include:

• Night sweats
• Chills
• Weight loss
• Fever

Ulcerative colitis¹²

Symptoms will depend on the location of the disease, generally present over weeks or months and mainly include diarrhoea, tenesmus, the passage of mucus, abdominal pain and rectal bleeding.

Recto

When only the rectum is affected, it is known as proctitis, and the symptoms are:

• Pass fresh blood
• Blood-stained mucus either mixed with stool
• Tenesmus
• Urgency
• The feeling of incomplete evacuation

Beyond the rectum

• Blood mixed with stool or grossly bloody diarrhoea
• Liquid stool containing blood, pus and faecal matter
• Nocturnal or after meals diarrhoea
• Lower abdominal discomfort

Crohn’s disease¹²

Unlike active bracelet colitis, Crohn's disease occurs acutely or chronically and usually generates fistulas or obstructions. Symptoms will depend on the location of the disease:

Ileocolitis

• Right lower quadrant pain relieves by defecation
• Diarrhoea
• Low-grade fever
• Mass the right lower quadrant of the abdomen
• Bowel obstruction
• Fistulas

Jejunoileitis

• Diarrhoea
• Anaemia
• Mlabsorcion
• Blocked disorders Bertha brand factors my
• Absorption of vitamin B12
• Fistulas

Colitis and perianal disease

• Low-grade fever
• Diarrhoea
• Abdominal pain
• Blood in the stool
• Feculent vomiting
• Abscess

Gastroduodenal disease

• Nausea
• Vomiting
• Epigastric pain

Extraintestinal symptoms¹⁴

Extra-intestinal symptoms most frequently affect the eyes, skin, joints, and other organs such as the pancreas, lungs, and liver.

Muskuloskeletal symptoms

The musculoskeletal system is affected in 46% of patients with IBD

Skin lesions

Skin lesions can be found in between 5 and 15%. The most frequent lesions are erythema nodosum and pyoderma gangrenosum.

Erythema nodosum

Erythema nodosum is characterized by pain, red inflammation, and an increase in the size of subcutaneous nodules on the extensor surfaces of the legs.

Pyoderma gangrenosum

Pyoderma gangrenosum presents as reddish nodules or pustules that turn into deep ulcers with a purplish border and pus.

Eye involvement

About 2 to 7% of the cases involve eye problems, the most common of which are anterior uveitis, scleritis, and episcleritis.

Hepatobiliary symptoms

Extraintestinal manifestations include primary sclerosing cholangitis and hepatitis.

Conclusion

IBD affects the gastrointestinal tract. There are two types: UC and CD, each with different signs and symptoms. Genes, environment, microbial changes in the gut, and immune mistakes all contribute to the disease's start. Symptoms range from abdominal pain and diarrhoea to extraintestinal manifestations like skin and joint issues. Diagnosis often involves colonoscopy and imaging, while treatment includes lifestyle changes, medication, and sometimes surgery. Early diagnosis and proper management are crucial for improving quality of life and reducing complications.