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Page: Investigation and Diagnosis
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Diagnosis is usually made on the basis of the location and severity of the pain, which is typically colic in nature (comes and goes in spasmodic waves). Radiological imaging is used to confirm the diagnosis and a number of other tests can be undertaken to help establish both the possible cause and consequences of the stone. Ultrasound imaging is also useful as it will give details about the presence of hydronephrosis (swelling of the kidney - suggesting the stone is blocking the outflow of urine). It can also be used to show the kidneys during pregnancy when standard x-rays are discouraged. About 10% of stones do not have enough calcium to be seen on standard x-rays (radiolucent stones) and may show up on ultrasound although they typically are seen on CT scans.
The relatively dense calcium renders these stones radio-opaque and they can be detected by a traditional X-ray of the abdomen that includes Kidneys, Ureters and Bladder—KUB. This may be followed by an IVP (Intravenous Pyelogram; IntraVenous Urogram (IVU) is the same test by another name) which requires about 50ml of a special dye to be injected into the bloodstream that is excreted by the kidneys and by its density helps outline any stone on a repeated X-ray. These can also be detected by a Retrograde pyelogram where similar "dye" is injected directly into the ureteral opening in the bladder by a surgeon, usually a urologist. Computed tomography (CT or CAT scan), a specialized X-ray, is considered the gold-standard diagnostic test for the detection of kidney stones, and in this setting does not require the use of intravenous contrast, which carries some risk in certain people (eg, allergy, kidney damage). All stones are detectable by CT except very rare stones composed of certain drug residues in urine. The non-contrast "renal colic study" CT scan has become the standard test for the immediate diagnosis of flank pain typical of a kidney stone. If positive for stones, a single standard x-ray of the abdomen (KUB) is recommended. This additional x-ray provides the physicians with a clearer idea of the exact size and shape of the stone as well as its surgical orientation. Further, it makes it simple to follow the progress of the stone without the need for the much more expensive CT scan just by doing another single x-ray at some point in the future.
Investigations typically carried out include:
* Microscopic study of urine, which may show proteins, red blood cells, pus cells, cellular casts and crystals.
* Culture of a urine sample to exclude urine infection (either as a differential cause of the patient's pain, or secondary to the presence of a stone)
* Blood tests: Full blood count for the presence of a raised white cell count (Neutrophilia) suggestive of infection, a check of renal function and if raised blood calcium blood levels (hypercalcaemia).
* 24 hour urine collection to measure total daily urinary volume, magnesium, sodium, uric acid, calcium, citrate, oxalate and phosphate.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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