Intravenous urogram

This invasive technique, also referred to as the intravenous pyelogram (IVP), involves injection of an intravenous bolus of an iodine-based radio-opaque solution (Conray or Hypaque) and taking sequential radiographs using ionizing radiation. To obtain the best concentration of the contrast in the kidneys, the patient may be dehydrated for a few hours before the test.

A plain abdominal radiograph or 'scout' film is taken initially to identify any renal stones that may be later obscured by contrast and to assess the bony skeleton for abnormalities.

Following the injection of intravenous contrast, radiographs are taken at 5 and 15min. After a further 20min, a further film is taken to demonstrate the KUB. Further films may be taken if particular features need to be assessed, for example oblique films or delayed films. Finally, the patient is asked to void and a post-micturition film is taken. If there is delayed renal function due to an obstructive hydronephro-sis, films at 12 or 24 h can be taken to demonstrate contrast at the level of obstruction.

Figure 19.3. CT scan demonstrating bilateral renal cysts.

Uses

• Crude assessment of renal function can demonstrate a non-functioning kidney.

• Anatomical demonstration of renal pelvis and calyces. Distortion may indicate a renal mass.

• Demonstration of hydronephrosis and the level of any obstruction.

Disadvantages

• Invasive and uses ionizing radiation.

• Can miss renal masses and does not differentiate between solid and cystic lesions.

• Limited use in renal failure, due to poor renal function or perfusion.

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