Investigations of Urinary Stones

Not all cases of flank pain, blood in the urine or calcifications on the abdominal x-ray are due to urinary stones. Conversely, uric acid and cystine stones are not seen on plain x¬rays. To confirm that you have a stone, further x-ray investigations are required.

Non-contrast computer tomography (CT) scanning is the investigative tool of choice for those suspected of having urinary stones. In those cases where urinary stones are not the cause of the pain, it can sometimes identify the diagnosis.

Alternatively, ultrasound together with an abdominal x-ray can diagnose urinary stone. Ultrasound of the kidneys can quantify the degree of obstruction caused by stones in the ureter and the severity of kidney damage (by assessing the thickness of the renal substance). However, ultrasound by itself cannot usually identify stones in the ureter. Together with an abdominal x-ray, it can strongly suggest (but not confirm) the diagnosis of ureteric stone if a calcification is seen on the x-ray along the path of the ureter and the ultrasound of the same side kidney shows dilatation i.e. obstruction. If there is also blood in the urine and a typical presentation of loin to groin pain, then we can almost be sure of the presence of ureteric stones.

In order to identify any underlying treatable cause of stone formation, blood is often taken to checkfor high levels of calcium and uric acid. If they are present, specific treatment will be recommended. Less often, 24-hour urine collection is taken to check on the urinary levels of calcium, oxalate and uric acid.