Final answer:
The best nursing diagnosis for a client who is anxious about an upcoming intravenous pyelogram due to lack of information is 'Anxiety related to lack of knowledge concerning intravenous pyelogram'.
Step-by-step explanation:
The most appropriate nursing diagnosis for a client who is expressing concern over a scheduled intravenous pyelogram and not knowing what to expect would be 'Anxiety related to lack of knowledge concerning intravenous pyelogram'. This diagnosis addresses the client's emotion of anxiety, specific to the intravenous pyelogram procedure itself, stemming from a lack of knowledge or understanding about what the procedure entails. It suggests the need for providing information and reassurance to the client to alleviate anxiety.