Which of the following investigation must be performed before giving contrast to the patient?

K.F.T is performed before giving contrast,as iodinated contrast agents and Gadolinium can be nephrotoxic so avoided in patients with elevated serum creatinine levels L.F.T is not done because all contrast agents are excreted kidney except USG contrast which is excreted by lungs. Urine specific gravity and serum electrolytes has no role in prediction of contrast induced Nephropathy.