Before undergoing IVP, a technologist will interview you about your medical condition, and especially your allergy history. You may also be asked questions about your test preparation.
The technologist will then tell you about the risks of receiving contrast material. Although reactions can be severe, risks are small. You will be asked to sign a consent form that affirms that all the risks have been explained to you.
Now, you are ready for your first film, which is just a picture of your abdomen and pelvic region taken before the dye is injected. The radiologists want to have a record of what your abdomen looked like before the contrast (which looks dense like stones) is injected. The technologist will probably feel for a number of landmarks on your body, such as your hips and breastbone, in order to obtain the best possible film. Then you will receive dye.
After the technologist has taken the film, it will take a few minutes before a readable scout film of the abdomen will be ready. IVPs require the injection of dye, so a record of what things look like before the dye was injected is needed. Also, if you have had a previous GI test, like an upper GI series or barium enema, residual material from those tests in your large bowel could completely cover important structures like the kidneys and make the test useless. The technologist should know that before the procedure in order to prevent the needless dye injections.
Having a chest x-ray, therefore, is a very different experience than having an IVP. IVP requires a larger dose of radiation and the injection of the contrast dye.
The dye that is used is a concern. A more complete discussion of contrast agents can be found at Dyes and Contrast. Most patients receiving dye do not even flinch with the newer agents that are being used. Very rare reactions range from a bad case of hives, to an asthma attack, to cardiac and respiratory collapse that can quickly result in death if the proper response is not supplied in a timely fashion.
What happens next varies. If you are the patient, what you want from a doctor here is to decide if you really need this test or if there are less invasive tests that would be as effective. Is there something in your history that suggests you might have a bad reaction to the dye, such as asthma or a prior adverse reaction? Does the scout film show what needs to be shown?
After the technologist has done the preliminary work and consulted with the radiologist, the dye will be injected by a nurse, technologist, or radiologist. Generally, IVP dye is injected by bolus, which means directly into the vein in concentrated 50 cc syringes; although there are probably still departments where the dye is "dripped in" over a longer time period through an IV bottle.
Years ago, you would have felt a flash of heat of varying intensity, you might have gotten a peculiar bitter taste in your mouth (a bit like sucking on a nickel), or you might have felt nauseated and gotten the dry heaves. Now, with the newer dyes, patients feel very little if anything at all. The experience is more like having a chest x-ray.
You may have nephrotomography. It sounds dreadful, but actually it is a very ingenious solution to a difficult problem. The purpose of an IVP is to see the kidneys and other urinary tract organs. Often though, the kidneys are obscured by material in the colon such as feces and gas.
Conventional x-rays of the abdomen show just a "through and through" view of the organs—the skin over the muscles, over the bowel, over the kidneys, and so on. By moving both the x-ray source and the x-ray film in certain arcs relative to each other, the radiologists can actually select a plane at which the x-ray picture will be most in focus—everything in front and everything behind that plane will be blurred. That is the essence of conventional tomography.
In nephrotomography, the focal plane is set on the middle of the kidneys. The technologist often obtains a "scout tomogram" to locate the patient's kidneys. If the renal outlines are very visable, the radiologist will get a few slices above or below the scouted plane. If they are not, adjustments are made. Most departments get their tomograms quite early in the sequence during the nephrogram phase, when the renal cortex is bright and lit up and the outlines are sharp.
Tomograms do add additional radiation to the IVP, so it becomes a risk/benefit question. Many practices avoid adding tomography to the exam of any woman of childbearing age unless absolutely necessary. Since the purpose of nephrotomography is primarily for looking for occult cancer, the extra radiation and extra expense are generally reserved for those patients who are most prone to develop cancer. As a general rule, departments often use an age of 35 to 40 cutoff and do not do tomography on younger patients. Patients suspected of passing ureteral stones most often do not need tomograms. For patients who are middle-aged and older, the tomograms are often worth the extra effort.
As the test starts to wind down, the IV will be removed from your vein. The technologist will take several films while you role around on the table. You will then be asked to get up and go to the bathroom. When you return, a final picture is taken, once the radiologist consents, you will be done.