Q. Hello, Dr. C. My name is William, I am seventy-seven years old, and I have been on a kidney dialysis machine three days per week for two years. At that time I was admitted to the hospital with a heart attack. I had an emergency cardiac cath and had stents placed in my heart. I did pretty well regarding my heart, but while I was in the hospital my kidneys stopped working. The doctors diagnosed acute renal failure and eventually concluded that it was caused by the dye used during the heart procedure. I have had some kidney problems in the past due to my high blood pressure, but they were never considered serious. I take medications for high blood pressure, gout, and mild diabetes. I had never heard of this problem, but I sure know about it now. Is what happened to me very common and could it have been prevented?

A. William, you ask a very good question. Tens of thousands of patients enter the healthcare system for a multitude of reasons and are given x-ray contrast medium during such tests as CT scans of the head, chest, abdomen, and pelvis, and vascular studies of the heart, aorta, and vessels of the arms and legs. For all of these patients there is the risk that the dye will injure the kidneys. For patients undergoing a cardiac angiogram such that you had, the risk of developing renal failure requiring dialysis is approximately four to eight per thousand patients. Clearly the most important factor in determining the risk of developing contrast-induced kidney injury after the angiogram or CT scan is the level of kidney function before exposure to the dye. In your case, this and several other issues are of concern. You stated that you have high blood pressure and that you had had some kidney problems in the past. I strongly suspect that you had more than just a little kidney trouble before your heart attack. In one study of patients with problems such as you have described, all had significant kidney dysfunction before receiving dye. Put another way, no patient with normal kidney function before dye exposure in a large clinical trial had a significant or lasting change in kidney function. Over the years of use of dyes during x-ray studies, several risk factors have been defined and allow physicians to assess the chances that the patient will have an adverse kidney event or end up on dialysis. Major factors include: age over 75 years, anemia, heart failure, cirrhosis, regular use of NSAID analgesics, diabetes, the amount of contrast used, and extent of kidney dysfunction. The kidney dysfunction does not have to be severe to pose a risk for a dye insult to the kidney. Other risk factors include the diabetic drug metformin, dehydration, low blood pressure during the hours of a heart attack, and a history of gout. The total number of risk factors relate to the odds of a kidney insult. In your case the known risk factors add up quickly and the odds are about 1:10-to 1:100 that you would have developed kidney dysfunction leading to dialysis. Considering that the cardiac angiogram was needed to perhaps save your life, is there anything that could have been done to prevent your specific case of acute renal failure due to the dye used? Since the exact means by which contrast dye harms the kidney is uncertain, there are no specific treatments that help beyond giving plenty of intravenous fluid before the test and giving as little dye as possible during the test. There is some data to support the use of dilute dye preparations. What should patients do in general to protect themselves from dye induced kidney damage? First, be sure you need the CT scan or angiogram in the first place. Too often, doctors order contrast scans when other, safer imaging studies will suffice. Second, be sure your doctor is aware of your medications such as diuretics, NSAIDS, and metformin. They should not be taken during the forty-eight hours before the test. If you are over seventy years of age and have some kidney dysfunction, both you and your doctor must think long and hard before proceeding with that CT scan. It may be useful to give plenty of IV fluids before hand and appropriate to check the kidney function both before and 24-48 hours after the exposure to the contrast agent. In general, contrast agents are safe and useful for diagnostic testing when kidney function is normal. As the population ages, however, the incidence of high blood pressure, diabetes, gout, and medication use increases and so does the risk of surviving a heart attack but losing your kidney function in the process of care. While in years past, x-ray departments posted signs Are you pregnant? They should also post a sign, Are your kidneys OK? I hope this answers your very important question. >