Ulcerative Colitis (UC) is an autoimmune disease causing inflammation of the large intestine (colon) and the rectum.

The inflammation occurs only in the innermost layer of the lining of the intestine.

It usually begins in the rectum and lower colon, but may also spread continuously to involve the entire colon. 



The difference between diarrhoea caused by infection and inflammatory bowel disease was first described in 1875.

For many years thereafter Inflammatory bowel disease (IBD) was not well understood and little research was being conducted into the causes and treatments of Crohn’s and Ulcerative colitis, much less a search for cures.

More recently, major scientific advances, specifically in the fields of genetics, immunology and microbiology, have led to a greater understanding of the underlying mechanisms involved in Ulcerative Colitis, resulting in the development of increasingly effective treatments.



While the exact cause of ulcerative colitis is not entirely understood, it is now known to involve an interaction between genes, the immune system and environmental factors.

The immune system usually attacks and kills foreign invaders, such as bacteria, viruses, fungi and other microorganisms.

However, in people with ulcerative colitis, the immune system mounts an inappropriate response to the large intestine, resulting in its inflammation.

This abnormal immune system reaction occurs in people who have inherited genes that make them susceptible to ulcerative colitis.

Unidentified environmental factors serve as the “trigger” that initiates the harmful immune response in the intestines.



As the lining of the intestine becomes inflamed and ulcerated, it loses its ability to adequately process food and waste or absorb water, resulting in loose stools (diarrhoea) and in severe cases weight loss.

Most people with ulcerative colitis experience an urgency to have bowel movements and have crampy abdominal pain.

Inflammation can cause small sores (ulcers) to form in the colon and rectum. These can join together and become large ulcers that bleed, resulting in bloody stools.

The symptoms of ulcerative colitis vary from person to person, may change over time and can range from mild to severe.

People with ulcerative colitis often go through periods when the disease is quiet with few or no symptoms (remission), alternating with times when the disease is active and causing symptoms (flares).

Symptoms related to inflammation of the GI tract:

  • Diarrhoea
  • Abdominal Pain
  • Rectal Bleeding
  • Urgent need to move bowels
  • A sensation of incomplete evacuation

General Symptoms that may also be associated with ulcerative colitis:

  • Loss of appetite
  • Weight loss
  • Fatigue
  • Night sweats 
  • Fever
  • Loss of normal menstrual cycle


Once ulcerative colitis has been diagnosed, the symptoms can often be effectively managed.

However, ulcerative colitis is chronic illnesses and changes are likely to occur over time.

Symptoms may recur at times and complications may develop. Quiescent UC can have a tendency to recur.



Complications of Ulcerative Colitis include:

• Heavy, persistent diarrhoea, rectal bleeding and pain

• Perforated bowel – chronic inflammation of the intestine may weaken the intestinal wall to such an extent that a hole develops

• Toxic megacolon – severe inflammation that leads to rapid enlargement of the colon

Complications Outside the GI Tract

Not all complications of ulcerative colitis are confined to the GI tract.

For reasons that are not entirely understood, some people develop symptoms that are related to the disease but affect other parts of the body.

The most common of these complications affect the skin and bones.

These extra-intestinal complications may be evident in the:

• eyes (redness, pain, and itchiness)

• mouth (sores)

• joints (swelling and pain)

• skin (tender bumps, painful ulcerations and other sores/rashes)

• bones (osteoporosis)

• kidney (stones)

• liver (primary sclerosing cholangitis, hepatitis and cirrhosis) – occurs rarely.

IBD is a complex disease that results from the interaction of an individual’s genes with environmental factors and the immune system.



Scientific evidence clearly points to the role of heredity in ulcerative colitis.

Studies have shown that 5% to 20% of affected individuals have a first-degree relative (parent, child, or sibling) with one of the diseases.

Children of parents with UC are at greater risk than the general population for developing the disease. The risk is higher when both parents have IBD. 


Environmental Triggers

The environmental factors that trigger ulcerative colitis are not known but several potential risk factors have been studied. 

Smoking: The risk of developing UC is decreased in current smokers compared with people who have never smoked.

Antibiotics: May increase the risk for UC.

Nonsteroidal Anti-Inflammatory Drugs (aspirin, ibuprofen, naproxen): May increase the risk of getting UC and may cause flares.

Appendicitis: Children who have undergone an appendicectomy (removal of the appendix) are less likely to develop ulcerative colitis later in life,

Diet: UC is not triggered by eating any one particular food but for some people, certain foods can aggravate symptoms.


Understanding Now

In the decades since Ulcerative Colitis was identified, significant scientific progress has been made in understanding these chronic inflammatory diseases.

Advances in basic science (particularly immunology, genetics and microbiology) have added to the knowledge about the causes of the diseases and have provided targets for developing new treatments.

In addition, the importance of the gut microbiome has been recognised.

The microbiome comprises all the microorganisms (bacteria, viruses, fungi and other microbes) that reside in or on the human body.

The vast majority of these microorganisms are useful for maintaining good health.

An important area of ulcerative colitis research involves identifying the constellation of bacteria that reside in the intestines and understanding how they communicate and interact within the intestines and with the immune system.



A greater understanding of the underlying mechanisms of ulcerative colitis has already led to the development of novel treatments, such as biologic agents used to treat people with moderate to severe UC.



1. The Facts about Inflammatory Bowel Disease. Crohn’s & Colitis Foundation of America. Nov 2014

2. https://www.crohnscolitisfoundation.org/about/our-beginning

3. Ephgrave K. Extraintestinal manifestations of Crohn’s disease. Surg Clin North Am. 2007;87(3):673-680.

4. Russell RK, Satsangi J. Does IBD run in families? Inflamm Bowel Dis. 2008;14(S2):S20-S21.

5. Noble CL, Arnott IDR. What is the risk that a child will develop inflammatory bowel disease if one or both parents have IBD? Inflamm Bowel Dis. 2008;14(S2):S22-S23.

6. Bennett RA, Rubin PH, Present DH. Frequency of inflammatory bowel disease in the offspring of couples both presenting with inflammatory bowel disease. Gastroenterology. 1991;100:1638-1643.

7. Noomen CG, Hommes DW, Fidder HH. Update on genetics in inflammatory disease. Best Pract Res Clin Gastroenterol. 2009;23(2):233-243.

8. Loftus EV, Jr. Clinical epidemiology of inflammatory bowel disease: incidence, prevalence, and environmental influences. Gastroenterology. 2004;126(6):1504-1517.

9. Bernstein CN. Assessing environmental risk factors affecting the inflammatory bowel diseases: a joint workshop of the Crohn’s & Colitis Foundations of Canada and the USA. Inflamm Bowel Dis. 2008;14(8):1139-1146.

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