Indications are diminishing due the introduction of CT urography (CTU), but the standard list includes:
1. Anatomic roadmap for kidneys, ureter and bladder
2. Evaluation of flank pain or renal colic
3. Evaluation of hematuria
4. Evaluation of urinary tract status post trauma
1. 1 day before exam- eat a light lunch and dinner.
2. Clear liquids after 8 PM the night prior to exam.
3. Magnesium citrate or other mild laxative, e.g. dulcolax, the night prior to exam.
4. NPO for 3 hours prior to exam.
Intravenous contrast is excreted by the kidneys via glomerular filtration. Following injection, there are 3 phases:
1. Total body opacification phase (TBO) when contrast is in the capillaries.
2. Nephrogram phase when contrast is in the renal parenchyma
3. Pyelogram phase when contrast is in the pelvicalyceal system, ureters, and bladder.
The size and shape of the kidneys are evaluated, and an assessment is made for renal masses. Opacification of both kidneys at the same time is a rough indicator of normal blood supply and function. The calyces, renal pelves, ureters and bladder are evaluated. These structures are examined sequentially by serial x-rays and should show symmetric filling without dilatations, narrowing, or filling defects.
Procedure: The bowel is prepped prior to the study to minimize the presence of gas and fecal material, which may obscure the urinary collecting system. A preliminary “scout” x-ray of the abdomen is obtained prior to contrast administration to identify calcified renal stones. An IV catheter is then inserted into an arm vein and contrast is administered. Serial x-ray images of the abdomen are obtained as the contrast moves through the urinary system. At the end of the exam, the patient goes to the bathroom to urinate and images of the post-void bladder are obtained. The exam usually takes about 1 hour.
Patient Comfort Level
1. Needle stick for the IV catheter.
2. Intravenous contrast may cause a feeling of warmth and a metallic taste in the mouth. Some patients get nauseated and may even vomit.
3. Adverse reactions may occur to IV contrast agents, ionic> nonionic.
An IVU involves radiation and intravenous contrast, and the contraindications are largely due to the necessity of limiting these.
1. IVU should be avoided in pregnant women unless absolutely necessary.
2. Nursing mothers should pump and discard breast milk for 24 hours after receiving intravenous contrast.
3. Patients with documented allergy to iodinated materials and intravenous contrast should not receive contrast. There are many accurate imaging modalities for the kidney that do not require contrast, e.g. non-contrast renal CT, US, MRI, or nuclear imaging.
4. Patients with renal insufficiency, especially if diabetic, or in renal failure should not receive IV contrast.
5. Contrast can lead to precipitation of Bence Jones protein and acute tubular necrosis in patients with multiple myeloma, especially when dehydrated.
6. Contrast is hyperosmolar and may worsen CHF.
7. Contrast is uricosuric and can worsen gout.
1. IVU is only a rough indicator of function. If both kidneys function simultaneously, they both may have decreased function or blood supply.
2. Small lesions in the kidney may be missed.
3. A normal IVU does not rule out significant abnormalities, especially in the bladder. IVU misses up to 33% of bladder tumors.