disease (IBD), which can affect any part of the GI tract, but it mostly starts in the terminal ileum. Ulcerative colitis an ulcerative form of colitis, is the other major inflammatory bowel disease which is restricted to the colon and rectum. Both of these IBDs can give an increased risk of the development of colorectal cancer. Ulcerative colitis is the most common of the IBDs Irritable bowel syndrome (IBS) is the most common of the functional gastrointestinal disorders. These are idiopathic disorders that the Rome process has helped to define. Giardiasis is a disease of the small intestine caused by a protist parasite Giardia lamblia. This does not spread but remains confined to the lumen of the small intestine. It can often be asymptomatic, but as often can be indicated by a variety of symptoms. Giardiasis is the most common pathogenic parasitic infection in humans. There are diagnostic tools mostly involving the ingestion of barium sulphate to investigate disorders of the GI tract. These are known as upper gastrointestinal series that enable imaging of the pharynx, larynx, oesophagus, stomach and small intestine and lower gastrointestinal series for imaging of the colon. In pregnancy Gestation can predispose for certain digestive disorders. Gestational diabetes can develop in the mother as a result of pregnancy and while this often presents with few symptoms it can lead to pre-eclampsia. History In the early 11th century the Islamic medical philosopher Avicenna wrote extensively on many subjects including medicine. Forty of these treatises on medicine survive, and in the most famous one titled the Canon of Medicine he discusses "rising gas". Avicenna believed that digestive system dysfunction was responsible for the overproduction of gas in the gastrointestinal tract. He suggested lifestyle changes and a compound of herbal drugs for its treatment. In 1497 Alessandro Benedetti viewed the stomach as an unclean organ separated off by the diaphragm. This view of the stomach and intestines as being base organs was generally held until the mid-17th century. In the Renaissance of the 16th century Leonardo da Vinci produced some early drawings of the stomach and intestines. He thought that the digestive system aided the respiratory system. Andreas Vesalius provided some early anatomical drawings of the abdominal organs in the 16th century. In the middle of the 17th century a Flemish physician Jan Baptist van Helmont offered the first chemical account of digestion which was later described as being