Inflammatory bowel disease (IBD) is an immune-mediated group of diseases affecting the  gastro-intestinal tract. This means that an individual's immune system becomes "confused" for some reason, and causes inappropriate inflammation. The group composes two main conditions:

• Ulcerative colitis
• Crohn's disease 

The causes are complex and not fully understood, but include:

• Genetic predisposition
• Infectious agents
• Environmental factors (e.g. medications, smoking)
• The composition of gut micro-organisms (microbiota).

IBD typically affects the bowel, but may have manifestations outside of this system, including liver, eye, skin and joint problems. Sometimes individuals suffering from IBD will present initially with one of these conditions.

There are no specific tests to diagnose ulcerative colitis and Crohn’s disease definitively. Diagnosis relies on a combination of clinical, endoscopic and histological findings. It may be very difficult to differentiate ulcerative colitis and Crohn's disease from one another, and other conditions may mimic inflammatory bowel disease also e.g. tuberculosis of the bowel. Making a correct diagnosis is vital, as this may have significant long-term health, financial and psychosocial implications for the individual.

The spectrum of severity of IBD also varies greatly. Some individuals have mild disease that requires minimal or no treatment. Others suffer from intractable disease with severe complications and disability. It is very important that those individuals having or at risk of severe disease are recognised early and treated aggressively.

Because of the complexity of this group of diseases, diagnosis and management of these should be handled by a gastroenterologist.