Kidney diseases and diseases of the urinary tract (ureter, bladder, urethra) require a variety of special examinations in order to make a correct diagnosis and therapy. Laboratory diagnostics include blood tests and various urine tests (physical, chemical, microscopic and bacteriological). Renal function tests can also enable the diagnosis of subtle kidney diseases. Sonography enables the kidneys to be visualized transcutaneously (externally) and the left kidney transrectally (internally). Ultrasound can also be used for a detailed diagnosis of the ureters, bladder and urethra. Endoscopy can be used to view the urethra, the bladder (Fig. 1) and the junctions of the ureters with the bladder. Biopsies of kidney tissue or altered tissue of the urinary tract can be taken either with special biopsy sticks or transendoscopically.