There are few things less evidence-based since medical antiquity than contrast-fear and contrast-management. We are slowly, slowly, as a field trying to correct long-held mistakes based on bad correlative science.
Intravenous iodinated contrast media are commonly used with CT to evaluate disease and to determine treatment response. The risk of acute kidney injury (AKI) developing in patients with reduced kidney function following exposure to intravenous iodinated contrast media has been overstated. This is due primarily to historic lack of control groups sufficient to separate contrast-induced AKI (CI-AKI; ie, AKI caused by contrast media administration) from contrast-associated AKI (CA-AKI; ie, AKI coincident to contrast media administration). Although the true risk of CI-AKI remains uncertain for patients with severe kidney disease, prophylaxis with intravenous normal saline is indicated for patients who have AKI or an estimated glomerular filtration rate less than 30 mL/min/1.73 m2 who are not undergoing maintenance dialysis. In individual high-risk circumstances, prophylaxis may be considered in patients with an estimated glomerular filtration rate of 30–44 mL/min/1.73 m2 at the discretion of the ordering clinician.
The risk of CI-AKI (née CIN) with iodinated contrast for GFR > 45 is zero and for 30-44 probably close to zero as well. If your patient would benefit from intravenous contrast, there are few reasons to avoid it when it will provide meaningful clinical value.
In related news, having one kidney does not matter for contrast safety if that kidney is functioning.