Contrast nephropathy is worsening of renal function after IV administration of radiocontrast and is usually temporary. Diagnosis is based on a progressive rise in serum creatinine 24 to 48 hours after contrast is given. Treatment is supportive. Volume loading with isotonic saline before and after contrast administration may help in prevention.
(See also Overview of Tubulointerstitial Diseases.)
Contrast nephropathy is acute tubular necrosis caused by an iodinated radiocontrast agent, all of which are nephrotoxic. However, risk is lower with newer contrast agents, which are nonionic and have a lower osmolality than older agents, whose osmolality is about 1400 to 1800 mOsm/kg (or mmol/kg). For example, second-generation, low-osmolal agents (eg, iohexol, iopamidol, ioxaglate) have an osmolality of about 500 to 850 mOsm/kg (or mmol/kg), which is still higher than blood osmolality. Iodixanol, a newer iso-osmolal agent, has an osmolality of 290 mOsm/kg (or mmol/kg), about equal to that of blood.
The precise mechanism of radiocontrast toxicity is unknown but is suspected to be some combination of renal vasoconstriction and direct cytotoxic effects, perhaps through formation of reactive oxygen species, causing acute tubular necrosis.
Most patients have no symptoms. Renal function usually later returns to normal.
Фактори ризику контрастної нефропатії
Risk factors for nephrotoxicity are the following:
Older age
Preexisting chronic kidney disease
High doses (eg, > 100 mL) of a hyperosmolar contrast agent (eg, during percutaneous coronary interventions)
Factors that reduce renal perfusion, such as volume depletion or the concurrent use of nonsteroidal anti-inflammatory drugs (NSAIDs), diuretics, or angiotensin-converting enzyme (ACE) inhibitors
Concurrent use of nephrotoxic medications (eg, aminoglycosides)
Diagnosis of Contrast Nephropathy
Serum creatinine measurement
Diagnosis is based on a progressive rise in serum creatinine 24 to 48 hours after a contrast study.
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 hours after the procedure
Presence of other atheroembolic findings (eg, livedo reticularis of the lower extremities or bluish discoloration of the toes)
Persistently poor renal function that may deteriorate in a stepwise fashion
Transient eosinophilia or eosinophiluria and low C3 complement levels (measured if atheroemboli are seriously considered)
Treatment of Contrast Nephropathy
Supportive care
Treatment is supportive.
Prevention of Contrast Nephropathy
Preventing contrast nephropathy involves avoiding contrast when possible (eg, not using CT to diagnose appendicitis) and, when contrast is necessary for patients with risk factors, using a nonionic agent with the lowest osmolality at a low dose.
When contrast is given, mild volume expansion with isotonic saline (ie, 154 mEq/L or mmol/L) is ideal; 1 mL/kg/h is given beginning 6 to 12 hours before contrast is given and continued for 6 to 12 hours after the procedure. For outpatient procedures, 3 mL/kg of isotonic saline can be given the hour before the procedure and 1 mL/kg of isotonic saline 4 to 6 hours after the procedure. A sodium bicarbonate (NaHCO3) solution may also be infused but has no proven advantage over normal saline. Volume expansion may be most helpful in patients with mild preexisting renal disease and exposure to a low dose of contrast. Volume expansion should be avoided in heart failure. Nephrotoxic medications are avoided before and after the procedure.
Acetylcysteine, an antioxidant, is sometimes given for patients at high risk but has no proven benefit.
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 and who require high doses of contrast; also, it is not practical. Therefore, this procedure is not recommended. Patients undergoing regular hemodialysis for end-stage kidney disease who require contrast do not need supplementary, prophylactic hemodialysis after the procedure.
Ключові моменти
Although most patients recover from use of iodinated radiocontrast without clinical consequences, all such radiocontrast is nephrotoxic.
Suspect contrast nephropathy if serum creatinine increases 24 to 48 hours after a contrast study.
Decrease the risk of contrast nephropathy, particularly in patients at risk, by minimizing the use and volume of contrast and expanding volume when possible.
