Worsening of kidney function on contrast nephropathy is best evaluated with?

S. Creatinine concentration usually begins to increase within 24 hours after contrast agent administration, peaks between days 3 and 5, and returns to baseline in 7-10 days. Serum cystatin C is also increased in patients with contrast-induced nephropathy. Nonspecific formed elements can appear in the urine, including renal tubular epithelial cells, pigmented granular casts, urate crystals, and debris. However, these urine findings do not correlate with severity.