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What is Inflammatory Bowel Disease (IBD)?

What is Inflammatory Bowel Disease (IBD)?

Inflammatory Bowel Disease (IBD) is a chronic condition characterised by inflammation of the gastrointestinal tract. There are two main types: ulcerative colitis (UC) and Crohn's disease (CD)1,2.

Ulcerative Colitis (UC)

Ulcerative colitis (UC) is an idiopathic inflammatory disorder primarily affecting the colon and rectum. It is characterised by chronic inflammation and ulceration of the mucosal lining of the colon. The exact cause of UC is unknown, but it is believed to involve a combination of genetic, environmental, and immune factors1,2,3. UC is also associated with an increased risk of colorectal cancer4.

Crohn's Disease (CD)

Crohn's disease (CD) is characterised by inflammation and damage to the lining of the digestive tract, which can occur anywhere from the mouth to the anus. CD is not limited to specific lesion sites and can involve any part of the digestive tract, including the small intestine, large intestine, and even the perianal area. The exact cause of CD is unknown, but it is believed to involve a combination of genetic, environmental, and immune factors. The harms associated with CD include complications such as strictures, fistulas, abscesses, and malnutrition1,2,5.

Epidemiology

Incidence6

  • The global age-standardised incidence was 4.97 per 100,000 person-years in 2019 approximately.
  • Geographic variations exist, with higher incidences in western and developed regions. 
  • High-income North America recorded the highest age-standardised incidence at 24.51 per 100,000 person-years in 2019 approximately.

Prevalence7

  • IBD accounted for 4.90 million cases globally in 2019 approximately.
  • The global age-standardised prevalence is 59.25 per 100,000 people approximately.
  • The age-standardised prevalence rate of high-income North America was 209.60 per 100,000 people approximately.

Demographic Profiles of IBD

Ulcerative Colitis (UC)8

  • Present at any time and at all ages. 
  • Majority of patients with UC are in the 30-40 years age group at diagnosis. 
  • Both males and females can be affected by UC, with no significant gender predilection.

Crohn's Disease (CD)9,10

  • Can affect individuals of any age.
  • Often diagnosed in young adults, between the ages of 20 and 29.
  • More common among women in Western countries, while in Asia, it appears to be more prevalent among men.

Possible Causes And Risk Factors

A combination of genetic, environmental, and immune factors10
Family history of the disease
Diet and lifestyle
Smoking may contribute to the onset of CD11
Microbial factors, including changes in gut bacteria
Inflammation and dysregulation of the immune system

Signs and Symptoms1

Ulcerative Colitis (UC)

Rectal bleeding
Diarrhoea
Urgency
Sense of pressure in rectum
Abdominal pain
Cramping and weight loss
Fever, anaemia, inflammation of other body parts (e.g. joints, skin, eyes)

Crohn's Disease (CD)

Rectal bleeding
Chronic diarrhea
Abdominal pain
Fatigue
Fever
Weight loss

Diagnosis

The severity of IBD varies from mild to severe, and is classified according to symptom severitys.

Level of Severity
Mild
Moderate
Severe

Typically, endoscopic procedures, in addition to tissue biopsy, would be conducted

Possible diagnostic tests for UC and CD:11,12,13

  • endoscopy and biopsy.
  • laboratory tests: C-reactive protein (CRP), Erythrocyte Sedimentation Rate (ESR).
  • biomarker tests: Anti-Saccharomyces cerevisiae antibodies (ASCA), Perinuclear Anti-Neutrophil Cytoplasmic (pANCA), Faecal calprotectin (FC).
  • Imaging tests, including computer tomography (CT) and magnetic resonance imaging (MRI).

Biopsy findings15

UC
  • Only mucosal layer involved, absence of granulomas
CD
  • Involves full thickness of intestinal tract, with presence of granulomas

Endoscopic findings12

UC
  • Involvement usually limited to the colon and rectum, continuous involvement
  • Typically: Oedematous mucosa, erythema, loss of vascular markings, mucosal friability
  • Severe: erosions, ulcers, spontaneous bleeding, mucosal atrophy
CD
  • Can involve the entire digestive tract
  • Discontinuous distribution of ulcers
  • Cobblestone appearance
  • Aphthous ulcers

Standard Treatment

Ulcerative Colitis (UC)3,16

Crohn's Disease (CD)5,16
Mild:
  • 5-Aminosalicylic acid (5-ASA): oral and/or rectal route
Moderate to severe:
    • Systemic steroids including budesonide
    • Immunomodulator: including thiopurines (such as azathioprine) and methotrexate
    • Biologics: anti-TNFα antibodies (e.g. adalimumab, golimumab, infliximab) and anti-α4β7 integrin monoclonal antibody (e.g. vedolizumab), and the anti-p40 (anti-IL-12/23) antibody (e.g. ustekinumab)
    • Oral small-molecules: Janus kinase inhibitors(e.g. tofacitinib, Upadacitinib) and s1p inhibitors (e.g. ozanimod)
    • Surgery to treat severe complications: e.g. toxic megacolon, colonic perforation, severe refractory haemorrhage, or when not responsive to medical therapy
Mild:
  • Systemic steroids: including budesonide
Moderate to severe:
    • Immunomodulators: such as azathioprine, 6-mercaptopurine (6-MP), and methotrexate 
    • Biologics*: anti-TNFα antibodies (e.g. adalimumab, certolizumab pegol, infliximab), anti-α4β7 integrin monoclonal antibody (e.g. vedolizumab, natalizumab), and the anti-p40 (anti-IL-12/23) antibody (e.g. Ustekinumab)
    • Oral small-molecule Janus kinase inhibitors (e.g.  Upadacitinib)
    • Surgery to treat severe complications: e.g. perforation, abdominal abscess, stricture
* Not all biologics or small molecules work for both diseases

Consequences2,4

  • A chronic condition with periods of remission and flare-ups. Severity ranges from mild to severe, significantly affecting patients' quality of life over the long term3,5
  • Increased risk of physical and mental health comorbidities3,5
  • UC has a higher risk of colorectal cancer4
  • CD has a higher risk of surgery17
Reference(s):

1 Hemstreet BA. Chapter 52: Inflammatory bowel disease. DiPiro’s Pharmacotherapy: A Pathophysiologic Approach, 12th Edition. McGraw Hill; 2023.

2 Schwinghammer TL. Chapter 26: Inflammatory Bowel Diseases. DiPiro’s Pharmacotherapy: A Pathophysiologic Approach, 12th Edition. McGraw-Hill; 2023. 

3 Rubin DT, Ananthakrishnan AN, Siegel CA, Sauer BG, Long MD. ACG clinical guideline: Ulcerative colitis in adults. Am J Gastroenterol. 2019;114(3):384-413.

4 Olén O, Erichsen R, Sachs MC, et al. Colorectal cancer in ulcerative colitis: a Scandinavian population-based cohort study. Lancet. 2020;395(10218):123-131. doi:10.1016/S0140-6736(19)32545-0

5 Lichtenstein GR, Loftus EV Jr, Isaacs KL, Regueiro MD, Gerson LB, Sands BE. ACG clinical guideline: Management of Crohn’s disease in adults. Am J Gastroenterol. 2018;113(4):481-517.

6 Zhou JL, Bao JC, Liao XY, Chen YJ, Wang LW, Fan YY, Xu QY, Hao LX, Li KJ, Liang MX, Hu TH. Trends and projections of inflammatory bowel disease at the global, regional and national levels, 1990–2050: a Bayesian age-period-cohort modeling study. BMC Public Health. 2023 Dec 14;23(1):2507.

7 Wang R, Li Z, Liu S, Zhang D. Global, regional and national burden of inflammatory bowel disease in 204 countries and territories from 1990 to 2019: a systematic analysis based on the Global Burden of Disease Study 2019. BMJ open. 2023 Mar 1;13(3):e065186.

8 Da Silva BC, Lyra AC, Rocha R, Santana GO. Epidemiology, demographic characteristics and prognostic predictors of ulcerative colitis. World Journal of Gastroenterology: WJG. 2014 Jul 7;20(28):9458.

9 Molodecky NA, Soon IS, Rabi DM, et al. Increasing incidence and prevalence of the inflammatory bowel diseases with time, based on systematic review. Gastroenterology. 2012;142(1):46–54.

10 Ng WK, Wong SH, Ng SC. Changing epidemiological trends of inflammatory bowel disease in Asia. Intest Res. 2016 Apr 27;14(2):111-9.

11 Ananthakrishnan AN. Epidemiology and risk factors for IBD. Nat Rev Gastroenterol Hepatol. 2015;12(4):205-217. doi:10.1038/nrgastro.2015.34

12 Lee JM, Lee KM. Endoscopic Diagnosis and Differentiation of Inflammatory Bowel Disease. Clin Endosc. 2016;49(4):370-375. doi:10.5946/ce.2016.090

13 Vermeire S, Van Assche G, Rutgeerts P. Laboratory markers in IBD: useful, magic, or unnecessary toys? Gut. 2006;55(3):426-431. doi:10.1136/gut.2005.069476

14 Costa F, Mumolo MG, Ceccarelli L, et al. Calprotectin is a stronger predictive marker of relapse in ulcerative colitis than in Crohn's disease. Gut. 2005;54(3):364-368. doi:10.1136/gut.2004.043406

15 Geboes K. What histologic features best differentiate Crohn's disease from ulcerative colitis? Inflamm Bowel Dis. 2008;14 Suppl 2:S168-S169. doi:10.1002/ibd.20598

16 Lontok E. Inflammatory Bowel Disease: A Giving Smarter Guide. Milken Institute; 2016. Available from: https://milkeninstitute.org/sites/default/files/reports-pdf/IBD-GSG-Final-6-14_2.pdf

17 Tsai L, Ma C, Dulai PS, et al. Contemporary Risk of Surgery in Patients With Ulcerative Colitis and Crohn's Disease: A Meta-Analysis of Population-Based Cohorts. Clin Gastroenterol Hepatol. 2021;19(10):2031-2045.e11. doi:10.1016/j.cgh.2020.10.039

 

This project is funded by the UGC Research Impact Fund (RIF)(reference number: R7007-22)
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