Historically, before the introduction and widespread adoption of computed tomography (CT) imaging, the intravenous pyelogram, or IVP, was the most commonly utilized radiographic study of the urinary tract. The IVP is an x-ray test in which a contrast agent (also termed "x-ray dye") is injected into a patient's vein; the contrast agent acts to outline the patient's kidneys, ureters, and bladder when x-rays are subsequently taken. Doctors would order an IVP for a number of reasons, including the evaluation of pain in their side, blood in the urine (hematuria), or other stone-related symptoms. In the present day, though, IVP is becoming less and less used (although there are still certain cases where it may be a helpful study), primarily as a result of the introduction of CT imaging. CT has become the x-ray study of choice for the evaluation of the urinary tract, because it can rapidly (even in a single breath-hold) image the entirety of the urinary tract. Since a CT scan presents its images as a cross-sectional view of the patient, oftentimes CT provides a greater amount of information than an IVP does, making CT a more cost-effective study. Furthermore, in many cases a CT imaging study does not require the administration of a contrast agent.
An IVP is generally performed in a hospital radiology department or a physician's office by an X-ray technologist and under the supervision of a radiologist or urologist. The patient will commonly be placed on a restricted diet 24 hours prior to the test and will be asked to urinate immediately prior to the test to ensure that the bladder is empty. The patient will then be asked to lie on their back and to remain still. A preliminary film, also called a "scout" film, of the abdomen and pelvis is obtained prior to the administration of intravenous contrast. The preliminary film ensures that the x-ray machine is calibrated correctly for the patient's size, and that there are no small stones present. Following intravenous injection of the contrast agent, a series of x-rays will be obtained, following the contrast material as it filters through the kidneys. Once the agent has filtered through the kidneys, it will pass down the ureters and into the bladder. Again, x-rays are obtained throughout this process, following the course of the contrast agent. The x-rays will be reviewed for evidence of tumors, cysts, stones or other structural and functional abnormalities.
At the conclusion of the study, the patient will be asked to urinate, so that a final set of images can be obtained to document how well the bladder empties. Once the IVP is over, the patient can immediately resume their daily activities.
The primary risk of an IVP test is a reaction to the x-ray dye. Such reactions are not common, but do occur in anywhere from 3 to 13 percent of people undergoing an IVP. In general, reactions are minor, and consist of symptoms such as flushing, nausea, or vomiting. These minor effects are usually treated successfully with medications such as antihistamines (drugs that reduce the effects of the body's inflammatory compound, histamine). In very rare circumstances, more severe complications-breathing difficulties, low blood pressure, swelling of the mouth or throat and even cardiac arrest-can occur.
Patients with certain health factors-a history of allergic reactions such as hay fever, asthma or hives, as well as congestive heart failure, and diabetes-may be at greater risk for reactions to the x-ray dye. In these situations, administering antihistamines or steroids prior to the exam will reduce the risk of a reaction to the x-ray dye. In addition, modern contrast agents, termed non-ionic contrast agents, are associated with a reduced risk of an allergic response.
An IVP is associated with a relatively low radiation exposure to the patient. However, a patient who is or may be pregnant should notify their physician prior to this examination as a fetus can be more susceptible to the risks associated with radiation.