Intravenous urography

Intravenous urography (IVU) is a radiographic study of the renal parenchyma, pelvicalyceal system, ureters and the urinary bladder. This exam has been largely replaced by CT urography. 

Terminology

The term "urography" refers to evaluation of the entire urinary tract, ie. kidneys, pelvicalicealpelvicalyceal systems, ureters and bladder. Intravenous pyelography (IVP) or excretory urography (EU) are in common usagecommonly used as alternative but less accurate terms. Some reserve the term "pyelography" to refer to retrograde opacification of the collecting system.

Indications

IVU would rarely be performed if CT is available. However important information can be obtained, such as:

• ureteric obstruction: severity, site and cause e.g. urolithiasis, most commonly as a delayed AP radiograph 1-24 hours after contrast-enhanced CT if obstruction and delayed excretion prevent CT diagnosis

• synchronous or metachronous upper tract tumour: detailed evaluation of calyceal morphology in patients with bladder transitional cell carcinoma (TCC)

• anatomical variants such as horseshoe kidney

• the course of the ureters

• both kidneys functioning and side-to-side comparison

Patient preparation

• fasting for 5 hours prior to the examination is preferred; laxatives to reduce faecal loading do not improve image quality ⁴

• check eGFR

• check for allergies and contrast medium reactions and obtain written informed consent according to hospital guidelines

• emergency medications and equipment must be available to treat clinically significant contrast medium reactions

Technique

Exposures in the 65-75 kV range optimise radiographic contrast, mA of 600-1000 and exposure time < 0.1 second.

There are a number of techniques for IVU examinations ⁴. An 18 or 19G gauge IV access is required for bolus injection of a water-soluble iodinated contrast agent; nonionic contrast medium has a better safety profile. A dose up to 1.5 ml/kg body weight is well tolerated. For suspected ureteric obstruction the following radiographs will suffice:

• control AP radiograph of the kidneys, ureters and bladder for calculi which can be obscured by contrast medium

• 3 minute post injection AP radiograph of the kidneys to show contrast medium beginning to appear in the pelvicalyceal systems. Unilateral absent excretion indicates obstruction. Cortical and medullary nephrogram is normally well seen at 3 minutes but may be reduced on the obstructed side

• 10 minute full-length AP radiograph, optional obliques

• full-length post-micturition radiograph to confirm ureteric obstruction and delineate the lower ureter which can be obscured by contrast medium in the bladder

• delayed full-length radiographs at 1 hour +/- 24 hours if the obstruction is severe and the ureter is insufficiently opacified

High-grade obstruction can significantly delay excretion. The nephrogram on the obstructed side will persist and increase in attenuation. If the site of obstruction is not delineated at 1 hour, then a 24-hour delay is indicated.

Contrast medium is heavier thenthan urine and this can be used to advantage. Bring the patient back in a chair and lie them prone to demonstrate the mid ureter. Then turn them supine to show the distal ureter.

The technique for synchronous or metachronous upper tract urothelial tumours or renal papillary necrosis includes detailed views of the pelicalycealpelvicalyceal systems.

• 5 minute AP radiograph of the kidneys then apply a lower abdominal compression band to distend the upper tracts

• AP and both oblique radiographs of the kidneys at 10 minutes

• full length AP radiograph and both obliques on compression release

• prone views are optional and to show the mid ureters

• multiple images help overcome the problem of non-visualisation of ureteric segments due to normal peristalsis

• AP radiograph of the full bladder with optional obliques

• AP full-length post void view

• obliques of the bladder if an abnormality is seen, such as ureterovesical junction calculus or bladder tumour ⁴

• if there is high-grade obstruction, excretion of contrast medium is delayed and further full-length radiographs at 1 hour and 24 hours are indicated. Prone and erect positioning may help to show the point of obstruction as contrast medium is heavier than urine

Compression is contraindicated in:

• renal trauma

• large abdominal mass

• abdominal surgery (post operative)

• abdominal aortic aneurysm