This test is performed quite quickly and easily. You will lie on a narrow table that slides into the center of the CT scanner. Most often, you will lie on your back with your arms raised above the head.Once you are inside the scanner, the machine's x-ray beam rotates around you. Modern "spiral" scanners can perform the exam without stopping.
A computer creates separate images of the belly area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the belly area can be made by stacking the slices together.
You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time. The scan should take less than 30 minutes.
Your doctor may order a CAT with oral or intravenous contrast for a clearer picture.
Oral contrast is often used to enhance CT images of the abdomen and pelvis. There are two different types of substances used for oral CT contrast. The first, barium sulfate, is the most common oral contrast agent used in CT. The second type of contrast agent is sometimes used as a substitute for barium and is called Gastrografin.
Barium contrast looks like and has a similar consistency as a milk shake. It is mixed with water and depending on the brand used, may have different flavors (for example, strawberry or lemon). Gastrografin contrast is a water-based drink mixed with iodine and has a tinted yellow color. When given orally, gastrografin may taste bitter.
Patients usually need to drink at least 1000 to 1500 cc (about three to four 12 oz. drinks) to sufficiently fill the stomach and intestines with oral contrast.
My last oral contrast was ordered due to upper abdominal pain and discomfort. As many of you, I do not do well after testing. It takes me a week or two to return to a semi-normal state. I was a bit surprised this time when I was inundated with flank, kidney pain for over two weeks. Knowing this was most likely attributed to the dyes i began to double my water intake. I also did a bit of research and found the following.
Lets try and understand a few nuances about contrast-mediated kidney damage, and what you can do about it. Radiological contrast can lead to a drop in the kidney's blood supply, and this is one of the ways that contrast hurts the kidneys. This is not fully understood, but could be related to certain vasoactive mediators (chemicals that make the blood vessels contract). These chemicals include something called "adenosine", and another called "endothelin".
In addition to reducing the blood supply to the kidneys, contrast could also be directly toxic to the kidneys. This could be related to the tendency of contrast to increase the level of certain destructive substances called "free oxygen radicals". This is the second major way in which contrast hurts the kidneys.
In spite of the above mechanisms in which contrast could possibly hurt the kidneys of a person receiving it, not everyone has the same risk of getting CIN. The rule of thumb is that the worse your baseline kidney function, the more likely are you to develop contrast nephropathy. Other factors that increase your risk are diabetes, heart failure, and certain types of cancers like myeloma. In fact, we now have a numerical risk calculator that incorporates a few of these risk factors and helps you come up with an objective number to predict the chances of your kidneys taking a hit from the contrast.
In an overwhelming number of cases, contrast nephropathy (which will be diagnosed by abnormalities in your kidney function number, creatinine within the first three days of receiving contrast) is mild. Even if it does develop, most patients will see their kidney function bounce back and normalize by about a week. However, if you do have preexisting kidney disease (CKD) or other risk factors mentioned above, this might not necessarily happen. Worsening of kidney disease to the point where you need dialysis is rare.
If the CT scan requiring the contrast is non-emergent, certain preventive steps can be taken. These can often minimize the risk of the kidneys getting hurt. Usually your kidney doctor would prescribe a regimen of intravenous fluids, and make sure that you are not dehydrated. Medications that could hurt your kidneys, like non-steroidal anti inflammatory drugs (NSAIDS) for instance, should be held. A drug called "acetylcysteine" interferes with production of the above mentioned free-oxygen radicals. However, it is now falling out of favor since most medical studies have failed to prove that it works. A newer antioxidant called trimetazidine has also shown some promise in contrast nephropathy prevention. Ask your nephrologist about what strategy might work best for you.
I found after increasing my water intake, unfortunately two days too late, my kidney function became less painful and eventually went back to its normal state. But I can tell you it overwhelmed me so much that I almost went in for another scan on my kidneys in the meantime. Always discuss options with your primary care provider before taking matters into your own hands.