High blood pressure
The kidneys have an automated system to control blood pressure, and blood pressure problems usually start after kidney cancer alters this careful control. There is a group of tumors that produce a substance called renin, which is usually secreted by the kidneys in response to a decrease in blood pressure, and its role is to increase and normalize blood pressure. However, renin-producing tumors would escape the normal control of the kidneys and synthesize renin even when it is not needed. As a result, patients end up suffering from hypertension, which sometimes counts as well as a risk factor for kidney cancer. Thus, having hypertension alone is not necessarily associated with kidney cancer, and you should look for medical advice if you are in doubt.