Introduction: Computed tomography kidneys, ureter and bladder (CTKUB) is the accepted gold standard investigation for suspected renal colic. Dose considerations are particularly pertinent in the context of detecting urolithiasis given the high risk of disease recurrence, which can necessitate multiple radiological examinations over the lifetime of a stone-former. We performed a systematic review of the literature to see whether there was any evidence that reducing the effective radiation dose of a CTKUB compromised the diagnostic accuracy of the scan.
Materials and methods: Relevant databases including MedLine, EMBASE, DARE and the Cochrane Library were searched from inception to October 2012. All English language articles reporting on prospective studies where non-contrast, low-dose CT (LDCT) was used to investigate adults (males and non-pregnant females) presenting with flank pain or suspected urolithiasis were included. LDCT was defined as an effective radiation dose <3 mSv per examination.
Results: Our initial search identified 497 records. After removing duplicates, 390 abstracts were screened, of which 375 were excluded, principally because outcomes of interest were not presented. Six papers remained for the final analysis, reporting on a total of 903 patients. Individual studies showed a prevalence of urolithiasis ranging between 36% and 88%, with additional pathologies found in 5-16%. The effective radiation dose of the LDCT techniques used ranged from 0.5 to 2.8 mSv. The sensitivity of LDCT for diagnosing stone disease was 90-97% with a specificity of 86-100%.
Conclusions: The sensitivity and specificity of CTKUB for diagnosing urolithiasis remains high, even when the effective radiation dose is lowered. LDCT may miss some small stones (<3 mm), especially in obese patients (>30 kg/m(2)), but in this group LDCT still identifies most alternative diagnoses. With at least one level 1A and two level 1B studies supporting the use of LDCT, there is Grade A recommendation for its use as the first-line investigation in suspected renal colic in non-obese patients.
Keywords: Computed tomography of the renal tract; low-dose computed tomography; renal colic; renal stones; urolithiasis.