Another issue is that prophylactic intravenous hydration is not without risk. Complications may occur, especially in those patients with cardiac and/or kidney disease, such as pulmonary oedema and/or cardiac failure which could lead to respiratory insufficiency. There is a considerable overlap between patients considered to be at risk of developing CIN and patients with at risk of complications from prophylactic intravenous hydration, and therefore this is a real concern in clinical practice. A study performed in a Dutch hospital using Dutch CIN prevention guidelines reported an incidence of serious complications of intravenous hydration of 1.4% in hydrated patients. The incidence of clinically relevant events after CIN is <1% when monomeric non-ionic low-osmolar iodinated contrast material is used, thus putting the appropriateness of the prophylactic treatment to question, and highlighting the importance of its evaluation against a proper control group not receiving intravenous hydration.