An intravenous pyelogram (IVP) is a radiological examination used to evaluate the urinary tract, which consists of the kidneys, ureters and bladder. Iodine-containing “contrast” is injected intravenously. It is excreted into the kidneys, passing through the ureters into the bladder. The iodine absorbs X-rays more efficiently than the surrounding tissues and in doing so, outlines the urinary tract. This allows the radiologist to visualise the entire tract and asses for abnormalities.
It is also more accurately known as an IVU or intravenous urogram.
What are the common uses of an IVP?
The IVP has become less important over recent years through improvements in other radiological techniques, such as ultrasound and CT. Despite this, the IVP still plays an important role in the investigation of patients who have blood in their urine, suspected kidney stones, complex urinary tract infections or structural abnormalities of their urinary tract.
How should I prepare?
Some hospitals require patients to take laxatives the day before, although this is not routine. This is to clear the overlying bowel. You should avoid food about 2-4 hours prior to the procedure due to the risk of nausea and vomiting after the contrast injection.
How is the procedure performed?
Standard X-rays of the abdomen and pelvis are taken while you lie on your back. After the initial views, the nurse or radiologist will inject the contrast into a vein on the hand or arm. Patients often describe a warm feeling rising up the arm into the body and sometimes a fleeting feeling of wanting to empty the bladder. You may experience a metal taste and mild nausea but vomiting is uncommon. Mild discomfort at the injection site is also sometimes described.
Repeat X-rays are taken every 10 to 20 minutes and depending on the abnormalities seen, an IVP can take anything from 30 to 90 minutes to complete. Additional “tomographic” views are often taken, in which the X-ray tube moves rapidly across the table during the exposure. This blurs the structures surrounding the kidneys, enabling closer scrutiny of any abnormalities. The last X-rays are usually taken while standing after the bladder has been emptied.
The main risks are due to the use of the contrast, which is also used in other X-ray examinations such as CT and angiography. Allergic reactions occasionally occur and range from mild itching and rash to – though very rarely – severe and life-threatening reactions. Allergic reactions are more common in patients who are asthmatic and with a history of drug sensitivity. If a patient has experienced a previous contrast reaction, it is very likely to reoccur. It is essential that such histories be conveyed, as precautions can be taken or an alternative examination arranged.
Contrast accumulates in poorly functioning kidneys, which can lead to irreversible damage. Patients particularly at risk are those older than 65, as well as those suffering from chronic renal failure, diabetes or high blood pressure. Some diabetic medications may also need to be stopped prior to the study.
Dehydration predisposes to renal impairment and an IVP should be avoided in patients who have had recent severe diarrhoea or vomiting, unless their fluids have been sufficiently replenished.
As with all X-ray examinations, there is slight risk due to the use of radiation. Excessive radiation exposure leads to the increased incidence of cancers, as well as hereditary and birth defects. The benefit of an appropriately requested IVP greatly outweighs the risks of the radiation exposure, with the exception of patients who are pregnant. An IVP should not be performed during pregnancy, so inform the doctor if you suspect you might be.
As mentioned, there are newer techniques which have decreased the use of IVP examinations. The findings are often not specific, and only demonstrate the urinary tract. Surrounding abnormalities can thus be missed, unless they directly affect the urinary tract. The long time it takes to perform an IVP compared to the other options is also a disadvantage.