Intravenous pyelogram

An intravenous pyelogram (also known as IVP, pyelography, intravenous urogram or IVU) is a radiological procedure used to visualise abnormalities of the urinary system, including the kidneys, ureters, and bladder.

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Procedure

  An injection of x-ray contrast media is given to a patient via a needle or cannula into the vein, typically in the arm. The contrast is excreted or removed from the bloodstream via the kidneys, and the contrast media becomes visible on x-rays almost immediately after injection. X-rays are taken at specific time intervals to capture the contrast as it travels through the different parts of the urinary system. This gives a comprehensive view of the patient's anatomy and some information on the functioning of the renal system.

Normal Appearances

Immediately after the contrast is administered, it appears on an x-ray as a 'renal blush'. This is the contrast being filtered through the renal capsule into the cortex. At an interval of 5 minutes, the renal blush is still evident (to a lesser extent) but the calices and renal pelvis are now visible. At 15 minutes the contrast begins to empty into the ureters and travel via peristalsis to the bladder which has now begun to fill. To visualise the bladder correctly, a post micturition x-ray is taken, so that the bulk of the contrast (which can mask a pathology) is emptied.

An IVP can performed in either emergency or routine circumstances.

Emergency IVP

This procedure is carried out on patients who present to an Emergency department, usually with severe renal colic and a positive haematuria test. In this circumstance the attending physician requires to know whether a patient has a kidney stone and if, is it causing any obstruction in the urinary system.

Patients with a positive find for kidney stones but with no obstruction are usually discharged with an a follow up appointment with a Urologist.

Patients with a kidney stone and obstruction, are usually required to stay in hospital for monitoring or further treatment.

An Emergency IVP is carried out roughly as follows:

• Plain KUB or Abdominal x-ray
• An injection of contrast media, typically 50mls.
• Delayed Abdominal x-ray, taken at roughly 15 minutes post injection

If no obstruction is evident on this film a post micturation film is taken and the patient is sent back to the Emergency department. If an obstruction is visible, a post micturation is still taken, but is followed up with a series of radiographs taken at a 'double time' interval. For example, at 30 mins post injection, 1 hour, 2 hours, 4 hours etc until the obstruction is seen to resolve. This time delay can give important information to the Urologist on where and how severe the obstruction is.

Routine IVP

This procedure is most common for patients who have unexplained microscopic or macroscopic Haematuria. It is used to ascertain the presence of a tumour or similar anatomy altering disorders. The sequence of images are roughly as follows:

• Plain or Control KUB image
• Immediate x-ray of the just renal area
• 5 minute x-ray of the just the renal area

At this point compression may or may not be applied (this is contraindicated in cases of obstruction).

• If compression is applied: a 10 minutes post injection x-ray of the renal area is taken, followed by a KUB on release of the compression.
• If compression is not given: a standard KUB is taken to show the ureters emptying. This may sometimes be done with the patient lying in a prone position.

• A post micturation x-ray is then taken. This is usually a coned Bladder view.

Image Assessment

The kidneys are assessed and compared for:

• Regular appearance, smooth outlines, size, position, equal filtration and flow.

The ureters are assessed and compared for:

• Size, a smooth regular and symmetrical appearance. A 'standing column' is suggestive of a partial obstruction.

The bladder is assessed for:

• Regular smooth appearance and complete voiding.

Contraindications

Historically, the drug metformin has been required to stop 48 hours post procedure, as it known to causes a reaction with the contrast agent. However the newest guidelines published by the Royal College of Radiologists suggests this is not as important for patients having <100mls of contrast, who have a normal renal function. If renal impairment is found before administration of the contrast, metformin should be stopped 48 hours before and after the procedure.^[1].

Diagnosis

• Kidney stones
• Renal cell carcinoma or RCC
• Polycystic kidneys
• Anatomical variations, i.e. horseshoe kidney or a duplex filtration system
• Obstruction (commonly at the Pelvic uretric junction or PUJ and the Vesico uretric junction or VUJ)

Other tests

An IVP can and should be used in conjunction with the following tests:

• Ultrasound
• Cystoscopy
• CT
• MRI
• Video cystometrography or VCMG
• Blood test
• Urine analysis

Treatment

Depending on the outcome and diagnosis following an IVP, treatment may be required for the patient. These include surgery, lithotripsy, ureteric stent insertion and radiofrequency ablation. Sometimes no treatment is necessary as stones <5mm can be passed without any intervention.

The Future of the intravenous pyelogram

The IVP is now becoming more and more obsolete. It has largely been taken over by CT, which give greater detail on anatomy and function.

See also

• Urodynamics
• Kidney stone
• Urology

References