Diagnosis

Imaging

Patients who have had previous stone episodes may recognise the characteristic pain of ureteric (renal) colic, but all patients require imaging for a diagnosis. For patients presenting to the emergency department, almost always they will get a non-contast CT (CT KUB) which is the most accurate test for diagnosing or exluding kidney stones. This involves a low dose of radiation, but with modern machines this dose is really minimised.

For patients presenting with milder symptoms e.g. mild loin pain, often to a general practitioner, often an ultrasound is prganised an first line investigation. This is often readily available and does not involve radiation, so is therefore a good choice as an intiial test. However it is not as reliable as CT scanning and can miss stones - particularly in the ureter as this is not seen well on ultrasound. It often overcalls stones as being present when they are in fact not proven on subsequent CT scan. Ultrasound is an excellent way of following patients up after treatment - or for those requiring long-term surveillance for new stone formation. Ultrasound is always used in pregnancy as it is safe and avoids radiation.

Plain x-ray (KUB) is used for tracking stones that are known to be present and visible - or for long-term monitoring of cerntain types of stones. However not all stones show up on x-ray and again it involves a low dose of radiation.

Other tests

1) Urine tests - all patients should have this checked. A urine dipstick will show the acidity (pH) which may be useful for understanding the underlying cause. It will also show any traces of blood - most patients with an acute stone will have some blood on testing - although 10% don't so it not totally reliable. A dipstick may also show signs of infection, and the sample can be sent off for culture to check for this.

2) Blood tests - all patients should have their full blood count (FBC) and kidney function checked. The sample can also be used to check the calcium and uric acid levels to make sure these are normal - as this may often give a clue as to why stones are forming.