What is Contrast-Induced Nephropathy?
There is some disagreement among medical professionals about what exactly constitutes contrast-induced nephropathy (CIN), a type of kidney damage, and how to treat it. Our current understanding is that CIN is a drop in kidney function that can be measured in two ways: either your creatinine levels (a waste product filtered out by the kidneys) increase by 25% compared to your normal level, or your serum creatinine increases by 0.5 mg/dL within two to three days after you receive contrast dye through an IV.
This decline in kidney function associated with the use of contrast dye is typically quick, usually happening within two to three days. However, if kidney function worsens up to seven days after contrast dye use, and there’s no other explanation for the kidney damage, it should still be considered CIN. Therefore, timing does play a role. After being exposed to contrast, creatinine levels usually peak between two and five days, and generally return to normal after about 14 days.
Contrast dyes, often containing iodine, are crucial for heart procedures such as coronary angiography and interventions. But with more heart procedures being done and more contrast dyes being used, especially in patients with higher risks like chronic kidney disease, diabetes, high blood pressure, there’s a growing worry about kidney damage due to CIN. A sudden drop in kidney function has become a frequent side effect of coronary angiography and interventions, mainly because of CIN or contrast-induced acute kidney injury.
What Causes Contrast-Induced Nephropathy?
Contrast-induced nephropathy, which is kidney damage following exposure to medical imaging contrast material, is most commonly found in people who already have chronic kidney disease. Roughly 8% of patients with moderate to severe kidney disease, 13% of those with severe to very severe disease, and 27% of those with end-stage kidney disease develop this condition after being exposed to contrast.
Other factors like old age, diabetes, heart failure, being female, peripheral vascular disease, high blood pressure, and low heart pump function can increase risk. Situations like acute coronary syndrome, low blood pressure, volume loss, certain medications, and anemia can also trigger this condition.
Contrast media can affect several parts of the kidney and cause harm through multiple ways. The four primary effects include:
1. Damage to the kidney’s filtering tubes,
2. Magnifying cellular damage through reactive oxygen species,
3. Increasing resistance to blood flow in the kidney,
4. Intensifying kidney blood vessel constriction, which is particularly harmful in patients with chronic kidney disease.
There are tools available to predict the risk of this condition before undergoing procedures that use contrast media, this can help in taking preventive measures. One such tool was developed by Gurm and his team, using data from over 68,000 procedures. This tool is available online.
A similar risk predictor is the Roxana Mehran score, which considers ten factors, including age, anemia, use of certain heart support devices, kidney function, low blood pressure, volume of contrast media used, heart failure, and diabetes. Each of these factors is assigned a point value, resulting in a total risk score. A score less than 6 indicates a 7.5% risk, while a score above 16 indicates up to a 57% risk.
Risk Factors and Frequency for Contrast-Induced Nephropathy
The number of people with diabetes and chronic kidney disease is increasing. These conditions can put people at risk for a sudden loss of kidney function after certain heart procedures. Presently, between 2% and 30% of people can get kidney damage from a contrast dye used in medical imaging, depending on how we define the condition. Fortunately, most of these cases fully recover in two to four weeks. The necessity for treatment to replace kidney function is relatively uncommon, affecting between 1% and 4% of patients, and less than half of these will need long-term treatment. The occurrence is above 2% in the general population. But this rate can get as high as 20% to 30% amongst individuals with risk factors for kidney disease. The risk of kidney damage from contrast dye is reportedly lower when a certain type of contrast dye is used.
Kidney damage from the dye is the third main cause of sudden kidney injury caused by medical treatment. The most common reason is reduced blood flow to the kidneys, leading to either injury before the kidneys or a condition called acute tubular necrosis. The number and kind of risk factors can directly increase the chances of kidney damage. The risk also changes based on the procedure, with rates being between 1.6% to 2.3% for diagnostic tests and 14.5% for coronary interventions.
- For people older than 60, the occurrence rate of this condition varies between 8% and 16%.
- In patients suffering from a severe heart attack who underwent heart procedures, being 75 years or older increases the risk of developing this condition.
Signs and Symptoms of Contrast-Induced Nephropathy
Contrast-induced nephropathy, also known as contrast-induced acute kidney injury, was first reported back in the 1950s. This was a serious kidney condition that led to death, following a routine radiography procedure (intravenous pyelography) in a patient suffering from a severe form of kidney disease associated with blood cancer (myeloma kidney). The condition leads to a temporary increase in creatine levels in about 15% of patients who undergo invasive procedures.
Even mild cases of contrast-induced nephropathy can be problematic, as they are linked with longer hospital stays, higher costs, and increased risk of dying in the short and long term. The occurrence of this condition varies, with reports indicating a rate between 7% and 11%, depending on the criteria used for the diagnosis, the group of people studied, and the healthcare setting. On average, a hospital stay related to contrast-induced nephropathy costs over $10,000 more. The condition is diagnosed by monitoring creatine levels two to three days after the patient is exposed to the contrast agent.
Those affected by contrast-induced nephropathy typically have a recent history of contrast administration, 24-48 hours before showing symptoms, during a diagnostic or therapeutic procedure like percutaneous coronary intervention. Contrast-induced acute kidney injury mostly does not result in reduced urination (nonoliguric).
A physical examination is valuable to exclude other potential causes of sudden kidney diseases. This could include cholesterol emboli, recognizable by symptoms like blue toes and a purple, mottled discoloration of the skin (livedo reticularis), or interstitial nephritis due to medicine, usually associated with a skin rash. Other signs could hint at a decrease in bodily fluids or a failing heart that is worsening (decompensated heart failure).
Testing for Contrast-Induced Nephropathy
Contrast-induced nephropathy is when your creatinine levels in your blood rise by at least 0.5 mg/dL or there’s a 25% increase from your normal results within 2 to 3 days after being exposed to a contrast medium. A contrast medium is a substance used in some types of medical imaging to make certain structures or areas inside your body stand out more.
The Kidney Disease Improving Global Outcome (KDIGO) has a different definition. According to KDIGO, stage 1 of this condition is characterized by a quick increase of creatinine to more than 0.3 mg/dL within 48 hours, relative rise by 50% or more from your normal results in 7 days or less, or reduced urine production to less than 0.5 milliliters per kilogram per hour for 6 to 12 hours. The severity of the condition can increase based on your creatinine levels, urine output, or the need for kidney replacement therapy.
Typically, in contrast-induced nephropathy, creatinine in your blood starts to increase within a day after you’ve received the contrast medium, it reaches its highest point between days 3 and 5, and then returns to normal levels in a week to 10 days. Serum cystatin C, used to check how well your kidneys are working, increases in people with contrast-induced nephropathy.
Some elements such as tubular epithelial cells, granular casts, uric acid crystals, and debris may appear in your urine, but they do not affect the severity of the condition. Also, urine osmolality, a measure of urine concentration, may become less than 350 mOsm/kg. Additionally, the fractional excretion of sodium (FENa), an index of your kidney function, could vary. In a few patients with severe contrast-induced nephropathy who produce little urine (oliguric), FENa is low early on, even if there are no signs of fluid loss.
Treatment Options for Contrast-Induced Nephropathy
The key strategy to lessen the chance of kidney damage caused by contrast dye should be put into action before the medical procedure involving contrast takes place. One such approach is careful hydration for patients with chronic kidney disease. This involves starting an intravenous saline drip, delivering 1 ml of fluid per kilogram of the patient’s weight each hour, starting 6 to 12 hours before the procedure and continuing afterwards. Some experts suggest a customized hydration protocol based on a patient’s specific heart function.
Sodium bicarbonate is often used to make the fluid in the kidneys more alkaline, preventing damage from unstable molecules known as free radicals. Typically, it’s given as an infusion at a rate of 3 ml per kilogram of body weight an hour before the procedure, and then continued at a slower rate for six hours afterwards. However, it’s worth noting that the exact length of this treatment is still debated among doctors. According to some research, hydration with sodium bicarbonate is more beneficial than saline alone.
Despite these benefits, a clinical trial found no clear advantage to using sodium bicarbonate routinely in patients going through heart-related procedures. Furthermore, a trial comparing a drug called acetylcysteine with a placebo found no difference between the two in preventing kidney damage from contrast dye or the need for dialysis.
There’s also some evidence suggesting that giving high-dose statins, specifically rosuvastatin, before the administration of contrast dye can help reduce the risk of kidney damage. However, this approach didn’t seem to work as well for patients already dealing with chronic kidney disease who were undergoing elective heart procedures.
Some other options, such as a drug called fenoldopam or a procedure called hemofiltration, didn’t show consistent benefits in trials. Conversely, taking vitamin C (ascorbic acid) can decrease kidney damage by 33%.
During the actual procedure, doctors may use smaller catheters, limit the amount of contrast dye used, avoid certain types of imaging, use specialized contrast agents of lower osmolarity, and ensure the maximum dose of contrast doesn’t exceed three times the estimated rate of kidney function.
What else can Contrast-Induced Nephropathy be?
When a doctor is trying to diagnose contrast-induced kidney damage (also known as contrast-induced nephropathy), they need to make sure it’s not actually one of several other possible conditions. These can include:
- Acute kidney failure, which is a sudden loss of kidney function
- Embolic renal disease, a condition where a blood clot blocks a blood vessel inside the kidney
- Interstitial nephritis, which is inflammation of spaces between the kidney tubes
- Acute tubular necrosis, a disease damaging the tube-like structures within the kidney
- Renal artery stenosis, a narrowing of arteries that carry blood to the kidneys
Each of these conditions can have similar symptoms, so it’s important for the doctor to run the right tests to make sure they’re treating the right condition.
What to expect with Contrast-Induced Nephropathy
Overall, patients’ health conditions like their baseline kidney function can greatly impact the prognosis following a contrast administration for imaging. Depending on the score table used, there might be a chance of developing Contrast-Induced Nephropathy (CIN). Generally, CIN is reversible, and a biopsy is rarely required for its diagnosis.
CIN usually resolves on its own. After contrast is administered, kidney function typically returns to normal within 7 to 14 days. However, less than a third of patients may experience some lingering kidney impairment.
Dialysis, a treatment that mimics some functions of the kidneys, is needed in less than 1% of CIN cases. This incidence slightly increases in patients who already have underlying kidney impairment or in patients who had a procedure called primary percutaneous coronary intervention for heart attack. But in diabetes patients with severe kidney failure, dialysis may be necessary in as many as 12% of cases. About 18% of CIN patients requiring dialysis end up needing it permanently. But most of these patients already had serious kidney issues and would likely have needed dialysis regardless of CIN development.
There’s growing understanding that Acute Kidney Injury (AKI) after contrast use can indicate Chronic Renal Failure (CRF) or End-Stage Renal Failure (ESRF). In a study involving 3986 patients who underwent a heart-related imaging process called coronary angiography, 12.1% developed AKI due to contrast, and 18.6% of those ended up with permanent kidney damage.
The prognosis is worse for patients who need dialysis, with almost 36% dying in hospital (compared to 7.1% of those not needing dialysis) and only 19% surviving over two years.
In a study focusing on the long-term death rate associated with CIN after the coronary procedure in patients with or without Chronic Kidney Disease (CKD), CIN was significantly linked with long-term death in the whole group and in patients with CKD, but not in those without CKD. The occurrence rate of CIN was found to be 11% in patients with CKD and 2% in those without CKD.
Possible Complications When Diagnosed with Contrast-Induced Nephropathy
The complications linked to contrast-induced nephropathy include:
- Acute kidney failure
- Sudden chronic kidney failure
- Allergic reactions
- Excess fluid in the body
- Lung congestion due to fluid buildup
- Contrast-induced thyroid dysfunction
Preventing Contrast-Induced Nephropathy
Contrast-induced nephropathy refers to a condition where the function of the kidneys gets mildly impaired due to the use of a contrast material (a type of dye used in some medical tests). Thankfully, this condition is often temporary and sees improvements between three to seven days. As recovery progresses, most patients’ kidney function returns to its original or near-original level before the contrast material was introduced. However, people with severe kidney disease might temporarily need kidney dialysis to help clean their blood after using a contrast material. Dialysis is a process that helps replace the function of the kidneys when they’re not working effectively.