Kidney Stones | Screening

Diagnosis

A patient presenting with pain consistent with a kidney stone, or any of the other symptoms listed above will be imaged to determine if a kidney stone is present, where it is located, and how large it is. Several different diagnostic imaging techniques are available to accomplish these goals:

• X-rays: X-ray imaging is able to see calcium that is in the majority of stones. A special test utilizing X-rays is an Intravenous Pyelogram (IVP) also known as an Intravenous Urogram (IVU). In this test, a special dye that is excreted by the kidneys is injected into the blood stream. When the kidneys filter it out of the bloodstream and into the urine, it outlines any stone that may be present, making it visible on an X-ray. An alternative procedure to an IVP is a Retrograde Pyelogram, which utilizes a dye similar to the IVP, but this time is injected directly into the ureters from the bladder by a urologist. The disadvantage to X-ray technology is that approximately 10% of stones do not have enough calcium to be seen on X-rays, and thus require alternative diagnosis methods.
• Ultrasound: Ultrasound is an easy to use and relatively inexpensive technology that can detect the swelling of the kidney (hydronephrosis) caused when a stone obstructs flow of urine. It can also be used in pregnancy when use of X-rays or other imaging technologies is not advised. Furthermore, ultrasound can visualize stones that are "radiolucent" because of their low calcium content
• Computed Tomography (CT): A CT scan without contrast is the gold-standard (best) diagnostic test for detecting kidney stones. This is because all types of kidney stones, except for extremely rare ones, are able to be seen on CT. If CT scan reveals a stone, your doctor will get a follow-up X-ray image in order to get a better sense of the orientation of the stone as well as its size and shape. This allows your doctor to follow-up on the stone using X-rays instead of requiring multiple CT scans.

In addition to imaging, your doctor may order several other tests to check your kidney function and determine the cause of your stone. These include:

• Blood tests: Blood tests can suggest if you have an infection due to your stone, check how well your kidneys are clearing waste from your body, and if you have high levels of salts that could cause stones (like calcium)
• Urine tests: Urine tests (urinalysis) can reveal the presence of proteins, red blood cells or bacteria as either a consequence of a stone or a cause of your pain. Your doctor may order a 24-hour urine collection test to determine critical information such as how much you drink per day as well as the concentrations of different salts involved in kidney stone formation such as calcium, oxalate, phosphate, magnesium, uric acid and citrate
• Analysis of the stone: You may be asked to urinate through a mesh screen device in order to catch your stone when it is passed so that your doctor can evaluate the stone at a later time.