Urology - Kidney Stone Centre
About Kidney Stones
Diagnosis and Testing
If the initial assessment of a patient suggests the presence of a kidney stone, tests can be done to aid diagnosis.
The urine is examined for the presence of microscopic blood, which is present in most cases of kidney stone.
Plain X-ray of the Abdomen
Stones can usually be seen on X-rays (except uric acid stones).
Intravenous Pyelogram (IVP)
Dye excreted into the urinary tract which can be seen on X-ray, is given to show the inside of the kidney and ureter. The kidney drainage may appear blocked by a stone and this test can prove whether an area which appears to be a stone is in the urinary tract.
An IVP is the most common X-ray test used to find a kidney stone. It will show all types of kidney stones, except for some uric acid stones, and gives pictures of the kidneys, the ureters, and the bladder. After regular X-ray of the abdomen is taken, X-ray dye is injected into a vein in the arm. The dye is filtered by the kidneys, and a number of X-rays are then taken which demonstrate the inner cavities of the kidney and the ureters.
An IVP is generally safe, but some people can experience flushing in the face or a strange taste in the back of the mouth. If you have ever had a reaction to a previous IVP, or if you have kidney failure, diabetes or an allergy to shellfish, tell your doctor. Some people are allergic to the IVP contrast dye, but with modern non-ionic contrast this is much less frequent than in the past. A minor allergic reaction may result in itchiness and a rash. More severe reactions are very rare, estimated to occur in one in 100,000.
This test can show whether the kidney drainage appears to be blocked by a stone and may demonstrate the stone in the urinary tract. This test alone is not adequate for shockwave lithotripsy as the lithotripter is equipped with X-ray and not ultrasound.
Recently, CT scans, which are specialized X-rays of the body, have been used to show the location of stones in the urinary tract.
Spiral CT scans are becoming more common in patients with kidney stones because they will show virtually all kidney stones, do not require any injection of contrast, and can be done quickly. However, the X-ray dosage with a CT is about 30 per cent more than with an IVP.
If none of the above X-rays have shown important information about the ureters, an urologist may insert a telescope into the bladder and inject X-ray contrast up the ureter to see it better. This can be done under local or general anesthesia, and may be done as part of the insertion of a stent [insert link to Stent or No Stent page].
Which Test Is Best?
No single test is the best for kidney stones. Generally either an IVP or a spiral CT scan is performed, and other tests are then done to get more information if necessary.
Prior to lithotripsy, you will need to have had either an IVP, a
CT or a retrograde pyelogram. An ultrasound by itself is not sufficient.