+ worsening of renal function after IV administration of radiocontrast
+ usually temporary
+ Diagnosis
+ + progressive rise in serum creatinine 24 to 48 h after contrast is given
+ Treatment is supportive
+ Volume loading with isotonic saline before & after contrast administration may help in prevention
+ All iodinated radiocontrast agents are nephrotoxic
+ risk is lower with newer contrast agents
+ + have a lower osmolality than older agents
+ + older agents osmolality is about 1400 to 1800 mOsm/kg
+ + 2nd-generation, low-osmolal agents (eg, iohexol, iopamidol, ioxaglate) have an osmolality of about 500 to 850 mOsm/kg, which is still higher than blood osmolality
+ + Iodixanol, the first of the even newer iso-osmolal agents, has an osmolality of 290 mOsm/kg, about equal to that of blood
+ The precise mechanism of radiocontrast toxicity is unknown
+ + suspected to be some combination of renal vasoconstriction & direct cytotoxic effects
+ + perhaps through formation of reactive O2 species, causing ATN.
+ Risk factors for nephrotoxicity are the following:
+ + Older age
+ + Preexisting renal insufficiency (eg, serum creatinine > 1.5 mg/dL)
+ + Diabetes mellitus
+ + Heart failure
+ + Multiple myeloma
+ + High doses (eg, > 100 mL) of a hyperosmolar contrast agent (eg, during percutaneous coronary interventions)
+ + Factors that reduce renal perfusion, such as volume depletion / the concurrent use of NSAIDs / ACE inhibitors
+ Diagnosis
+ + progressive rise in serum creatinine 24 to 48 h after a contrast study
+ + Most patients have no symptoms
+ + Renal function typically later returns to normal.
+ After femoral artery catheterization, contrast nephropathy may be difficult to distinguish from renal atheroembolism
+ + Factors that can suggest renal atheroemboli include the following:
+ + + Delay in onset of increased creatinine > 48 h after the procedure
+ + + Presence of other atheroembolic findings (eg, in skin, toes)
+ + + Persistently poor renal function
+ + + Transient eosinophilia / eosinophiluria & low complement levels (measured if atheroemboli are seriously considered)
+ Treatment is supportive
+ Prevention
+ + avoiding contrast when possible (eg, not using CT to diagnose appendicitis)
+ + when contrast is necessary, using the agent with the lowest osmolality for patients with risk factors
+ + When contrast is given
+ + + mild volume expansion with isotonic NaCl (ie, 154 mEq/L) is recommended
+ + + 1 mL/kg/h is given beginning 6 to 12 h before contrast is given & continued for 6 to 12 h after the procedure
+ + + Infusion of NaHCO3 has no proven advantage over normal saline & may even be harmful
+ + Nephrotoxic drugs are avoided before & after the procedure.
+ + + Acetylcysteine is an antioxidant that may be helpful
+ + + protocols vary
+ + + acetylcysteine, 600 mg po bid the day before & the day of the procedure, may be given, combined with NaCl infusion
+ + + Acetylcysteine & volume expansion may be most helpful in patients with mild preexisting renal disease & exposure to a low dose of contrast
+ + Periprocedural continuous venovenous hemofiltration
+ + + has no proven benefit compared with other less invasive strategies in preventing acute kidney injury in patients who have chronic kidney disease & who require high doses of contrast
+ + + is not practical
+ + + is not recommended
+ + Patients undergoing regular hemodialysis for end-stage renal disease who require contrast do not need supplementary, prophylactic hemodialysis after the procedure
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