Idiopathic inflammatory bowel disease (IBD) is a group of disorders whose common feature is inflammation of the gastrointestinal tract, including Crohn's disease (CD) and ulcerative colitis (UC). The purpose of this article is to review the Saxon literature regarding the epidemiology, pathogenesis and diagnosis of IBD. In recent years, the incidence of CD seems to be increasing, while that of UC remains unchanged. The genetic predisposition, the external environment, the intestinal microbial flora and the immune responses are involved in the pathogenesis of IBD. Most of the clinical symptoms and signs of IBD are common in all categories. No laboratory test is pathognomonic for IBD, and faecal calprotectin is a more reliable biomarker regarding diagnosis than other inflammatory markers. There are many imaging modalities, with most recent the capsule endoscopy, each of which is superior to the other depending on the stage and manifestations of the disease. Lifestyle changes in recent decades have led to an increased incidence in IBD in childhood. Advances in biomedical technology have led to new methods, laboratory and imaging, resulting in a more reliable diagnostic approach.