Making the invisible visible In the early years of the 1960s, Dr. Franz Köhler Chemie GmbH was already expanding its portfolio with ionic x-ray contrasting agents for conventional intravascular and oral x-ray diagnostics. In the following years, the company developed its own patented ionic x-ray contrast agent PERITRAST^®. In contrast to other x-ray contrast agents from different suppliers that were available at the time, the cation used was not sodium or meglumine, but for the first time an endogenous amino acid, namely ‘lysine’. Despite the then German Federal Health Agency’s inadequately justified ban on the intravascular application of ionic x-ray contrast agents in the 1990s, which significantly reduced the sales of the very well tolerated PERITRAST^®, the product continues to be used both orally and rectally. In the 1980s, non-ionic x-ray contrast agents started to dominate the market. In 2012, Koehler took over the distribution of the non-ionic x-ray contrast agent CETEGNOST^® for Germany. What are x-ray contrast agents used for? In x-ray images, e.g. blood vessels or internal organs such as the stomach or intestines, the bile ducts, the urinary bladder and the urinary tract can only be identified when a mixture of a contrast agent and the respective body fluid flows through them or when they are filled with it. The contrast agent serves to increase the so-called “x-ray density” of the mentioned organs compared to the surrounding body components, which makes the tissue to be examined more clearly visible in the X-ray image. Contrast agents can be introduced directly into the part of the body that is to be imaged. For example, the patient can drink the substance, or a gastric tube can be used to introduce it into the stomach. Catheters (rigid or flexible tubular instrument) can be used to deliver the x-ray contrast agent into the urinary bladder or into a blood vessel. The contrast agent can also be injected into a vein in the arm, in which case the substance enters the organ to be examined via blood vessels. The latter method is used, for example, for imaging the kidneys (excretory urography). X-ray contrast agents may also be used in computed tomography, with the help of which numerous structures can be assessed after intravenous administration.