Inflammatory Bowel Diseases – Ulcerative Colitis, Crohn's Disease

The bowels are made up of the small intestine and large intestine which are the longest parts of the digestive tract (alimentary tract or gut). The intestines are important sites of digestion and absorption of nutrients and the formation of waste material that is evacuated from the bowels as feces. Like the rest of the gut, it has a multi-layered wall that is somewhat similar in structure from mouth to anus. Within the bowels are massive populations of bacteria which help with digestion and absorption of nutrients but usually do not harm the bowels.  This naturally-occurring ‘good’ bacteria is known as the normal intestinal flora. The bowels are affected by a number of insults, from infectious to mechanical and chemical, but is usually able to recover once the causative factor is removed.


Inflammatory bowel disease (IBD) is a chronic condition that is associated with inflammation of the bowels. There are two main types of IBD known as Crohn’s disease and ulcerative colitis. Both these conditions primarily affect the large intestine and are largely similar in pathogenesis. There is often a family history indicating a genetic predisposition but this may only be triggered at certain times in life by as yet unknown factors. IBD more commonly starts in the teen years and early adulthood but may begin earlier or later in life. It is not uncommon for it to remain undiagnosed for periods of time with mild symptoms and mistaken for irritable bowel syndrome (IBS) without proper diagnostic investigation.

Ulcerative Colitis

Ulcerative colitis always involves the rectum and also the colon but does not extend further. There is diffuse inflammation of the affected area with shallow broad ulcers.

Crohn’s disease

Crohn’s disease mainly affects the colon and ileum (terminal part of the small intestine) but can involve any part of the gut from the mouth to the anus. Inflammation is usually patchy (skip lesions) with deep and narrow ‘knife-like’ ulcers.


The exact cause of IBD is unknown and there are several hypotheses surrounding the mechanism. It is believed that inflammatory bowel disease is actually a combination of these mechanisms. The main underlying factor, however, is a genetic susceptibility. It appears that the inflammation is immune-mediated as the immune response of the mucosal epithelium lining the bowels is defective. This may be associated with dysfunction in the normal cell barrier or triggered by the naturally-occurring bowel bacteria. Inflammation is limited to the superficial layers of the bowel in ulcerative colitis but extends through the entire thickness of the bowel wall in Crohn’s disease.


Various triggers have been identified but these factors may be individual to each patient :

  • Cigarette smoking
  • Spicy foods
  • Dairy
  • High fibers foods
  • Processed and preserved meats
  • Alcohol
  • Acute gastrointestinal infections

Signs and Symptoms

Diarrhea is the hallmark of acute flareups of IBD. In ulcerative colitis this is usually bloody diarrhea often with stringy mucus while Crohn’s disease is also characterized by diarrhea which is watery and large volume but without blood or mucus. A patient may be largely asymptomatic during the remission phases.

Other signs and symptoms of IBD includes :

  • Abdominal discomfort or pain
  • Abdominal cramps
  • Lack of appetite
  • Fever
  • Weight loss (more prominent in Crohn’s disease)
  • Other clinical features not isolated to the bowels (extra-intestinal manifestations) like eye inflammation, joint pains, mouth sores and skin rashes.

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