Contrast nephropathy refers to the worsening of kidney function due to the administration of iodinated radio-contrast medium usually through intravenous route. However, some of the cases of contrast nephropathy occur with intra-arterial administration. It is a serious complication of angiographic procedures.
It is not clear how a radio-contrast material causes toxicity to the nephrons of the kidney. However, their effect is mainly due to high osmolarity. The possible mechanisms include:
- constriction of blood vessels that supply blood to the kidneys
- formation of reactive oxygen species which are cytotoxic, which may cause acute tubular necrosis of the kidneys
- a programmed cell death in the kidneys, known as apoptosis
Usually, most of the patients with contrast nephropathy do not show any symptoms even before the kidney function returns to normal. Only laboratory values help in identifying the condition.
The following patient or procedure-related factors can increase the risk of developing contrast nephropathy:
- Use of high doses of hyperosmolar contrast materials
- Repeated exposure to contrast agent within 72 hours
- Concomitant use of certain medicines such as NSAIDs, ACE inhibitors, and diuretics
- Diabetes mellitus
- Older age (especially above 75 years)
- A history of chronic kidney disease (CKD)
- Kidney transplantation
- Heart failure
- Liver failure
- Multiple myeloma
The diagnosis of contrast induced nephropathy involves the measurement of serum creatinine levels over a period of 24 to 48 hours after the administration of the contrast material. There will be a progressive increase in the serum creatinine.
A differential diagnosis may be necessary in patients who undergo femoral artery catheterization to distinguish renal artheroembolism from contrast nephropathy.
Contrast nephropathy is self-limiting in most of the people with the serum creatinine returning to the normal values in 7-10 days. Usually a supportive treatment is provided for contrast nephropathy. The main aim of the treatment is to rehydrate the body and improve the volume and electrolyte balance.
The following are the treatment approaches of contrast nephropathy:
- Low risk – oral fluids are given to prevent volume depletion
- Medium risk – intravenous (IV) injections of 0.9% normal saline are given 12 hours before and after administering the contrast agent. If the creatinine levels are 25% above the baseline value, then further monitoring is required after 5 days of the procedure
- High risk – along with 0.9% normal saline IV injection, 600 mg of N-acetyl cysteine (NAC) is given orally, twice daily. This is given three days before and one day after the procedure. Further, the creatinine levels are noted at baseline, and are monitored after 48 hours, five days and ten days.
Additionally, the doctor regularly monitors the kidney function while giving the above treatment.
In some patients, dialysis or renal replacement therapy is necessary to remove the contrast material. However, this is needed only for a short time.
Contrast nephropathy is one of the common causes for hospital-acquired acute kidney failure (AKI). It accounts to about 10% of all the cases. Contrast nephropathy increases the risk of hospitalization. Even in patients who do not need dialysis, there is an increased risk of mortality within 1-year after developing contrast nephropathy.
Prevention is the cornerstone of management of contrast nephropathy. The best possible ways to prevent contrast nephropathy are as follows:
- Avoiding the use of contrast material whenever possible. For example avoiding CT scan to diagnose conditions such as appendicitis.
- Giving isotonic saline solution at least 6-12 hours before and after giving the contrast medium to cause mild volume expansion. However, volume expansion is not advisable for heart failure patients.
- If use of contrast material is not avoidable, then newer contrast agents which are non-ionic and less nephrotoxic compared to the traditional iodinated contrast agents should be used.
- Avoiding the use of nephrotoxic drugs such as nonsteroidal anti-inflammatory drugs (NSAIDs). However, avoiding the use of diuretics or angiotensin-converting enzyme inhibitors (ACE) inhibitors is not recommended.
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