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An Example of an IVU radiograph
An Example of an IVU radiograph
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 to 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:
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:
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.
The kidneys are assessed and compared for:
The ureters are assessed and compared for:
The bladder is assessed for:
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.
An IVP can and should be used in conjunction with the following tests:
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 IVP is now becoming more and more obsolete. It has largely been taken over by Computed tomography (CT), which gives greater detail on anatomy and function.
IVU has been largely replaced by Ultrasound and more recently by MRI. Both these modalities as against IVU and CT scan do not use ionising radiation (X Rays)that are known to be carcinogenic and teratogenic. Also the Iodinated contrast medium used in CT scan and IVU can cause severe reactions including anaphylactic reaction, that can be fatal in up to 1 in 25000 individuals.
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