(See also Overview of Tubulointerstitial Diseases Overview of Tubulointerstitial Diseases Tubulointerstitial diseases are clinically heterogeneous disorders that share similar features of tubular and interstitial injury. In severe and prolonged cases, the entire kidney may become... read more .)
Contrast nephropathy is acute tubular necrosis Acute Tubular Necrosis (ATN) Acute tubular necrosis (ATN) is kidney injury characterized by acute tubular cell injury and dysfunction. Common causes are hypotension or sepsis that causes renal hypoperfusion and nephrotoxic... read more 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, 2nd-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, the first of the even newer iso-osmolal agents, 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.
Risk factors for contrast nephropathy
Risk factors for nephrotoxicity are the following:
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 drugs (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 Renal Atheroembolism Renal atheroembolism is occlusion of renal arterioles by atherosclerotic emboli, causing progressive chronic kidney disease. It results from rupture of atheromatous plaques. Symptoms are those... read more . 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
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 Heart Failure (HF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular (LV) failure causes shortness of breath and fatigue, and right ventricular (RV) failure causes peripheral and abdominal... read more . Nephrotoxic drugs 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 Chronic Kidney Disease Chronic kidney disease (CKD) is long-standing, progressive deterioration of renal function. Symptoms develop slowly and in advanced stages include anorexia, nausea, vomiting, stomatitis, dysgeusia... read more and who require high doses of contrast; also, it is not practical. Therefore, this procedure is not recommended. Patients undergoing regular hemodialysis Hemodialysis In hemodialysis, a patient’s blood is pumped into a dialyzer containing 2 fluid compartments configured as bundles of hollow fiber capillary tubes or as parallel, sandwiched sheets of semipermeable... read more for end-stage renal disease who require contrast do not need supplementary, prophylactic hemodialysis after the procedure.
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.