An intravenous pyelogram or IVP for short is a radiological procedure used to visualize abnormalities of the urinary system, including the kidneys, ureters, and bladder.
An injection of x-ray contrast medium 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.
Immediately after the contrast is administered, it appears on an x-ray as a ‘renal blush’. This is the contrast being filtered through the cortex. At an interval of 3 minutes, the renal blush is still evident (to a lesser extent) but the calyces and renal pelvis are now visible. At 9 – 13 minutes the contrast begins to empty into the ureters and travel to the bladder which has now begun to fill. To visualize 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 be performed in either emergency or routine circumstances.
This procedure is carried out on patients who present to an Emergency department, usually with severe renal colic and a positive hematuria test. In this circumstance the attending physician requires to know whether a patient has a kidney stone and if it is causing any obstruction in the urinary system.
Patients with a positive find for kidney stones but with no obstruction are usually discharged with 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 50 ml;
delayed Abdominal x-ray, taken at roughly 15 minutes post injection.
If no obstruction is evident on this film a post-micturition film is taken and the patient is sent back to the Emergency department. If an obstruction is visible, a post-micturition film is still taken, but is followed up with a series of radiographs taken at a “double time” interval. For example, at 30 minutes post-injection, 1 hour, 2 hours, 4 hours, and so forth, 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.
This procedure is most common for patients who have unexplained microscopic or macroscopic hematuria. It is used to ascertain the presence of a tumour or similar anatomy-altering disorders. The sequence of images is roughly as follows:
plain or Control KUB image;
immediate x-ray of just the renal area;
5 minute x-ray of just the renal area.
At this point, compression may or may not be applied (this is contraindicated in cases of obstruction).
In pyelography, compression involves pressing on the lower abdominal area, which results in distension of the upper urinary tract.
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-micturition x-ray is taken afterwards. This is usually a coned bladder view.
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.
Historically, the drug metformin has been required to stop 48 hours pre and post procedure, as it known to cause 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.