Contrast-Induced Nephropathy Workup

Updated: Dec 18, 2018
  • Author: Anita Basu, MD, FACP; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Workup

Approach Considerations

In contrast-induced nephropathy (CIN), the serum creatinine (SCr) 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 (which has been suggested as a surrogate marker of renal function in lieu of SCr) is increased in patients with CIN.

Nonspecific formed elements can appear in the urine, including renal tubular epithelial cells, pigmented granular casts, urate crystals, and debris. However, these urinary findings do not correlate with severity.

Urine osmolality tends to be less than 350 mOsm/kg. The fractional excretion of sodium (FENa) may vary widely. In the minority of patients with oliguric CIN, the FENa is low in the early stages, despite the absence of clinical evidence of volume depletion.

Histology

Contrast media cause direct toxic effects on renal tubular epithelial cells, characterized by cell vacuolization, interstitial inflammation, and cellular necrosis. In one study, these characteristic changes, called osmotic nephrosis, were observed in 22.3% of patients undergoing renal biopsy within 10 days after contrast exposure. [30]