Systematic review and meta-analysis of the diagnostic accuracy of low-dose computed tomography of the kidneys, ureters and bladder for urolithiasis.

Renal colic is a common clinical condition which is often investigated with a CT of the kidneys, ureters and bladder (CTKUB). Recent technological improvements have allowed a reduction in dose with the emergence of low-dose CTKUB (LD-CTKUB) techniques. The present meta-analysis aims to determine the diagnostic accuracy of LD-CTKUB in the diagnosis of clinically significant uroliths. A systematic review was performed using nine electronic databases from their dates of inception to May 2016. Inclusion criteria included studies reporting comparative outcomes using LD-CTKUB with a dose less than 3 millisieverts compared to an imaging gold standard or clinical and surgical evaluation. The primary endpoint was detection of a urolith ≥3 mm where specified and any urolith when size was unspecified. Twelve studies were identified according to selection criteria, involving 1250 patients. LD-CTKUB demonstrated a pooled sensitivity of 93.1% (95%CI 91.5-94.4), specificity of 96.6% (95%CI 95.1-97.7%), positive likelihood ratio of 19.9 (95%CI 12.7-31.2), negative likelihood ratio of 0.05 (95%CI 0.02-0.10) and AUC of 0.9877 in the detection of clinically significant uroliths. Although 86 alternative diagnoses were noted across seven studies, none assessed the accuracy of LD-CTKUB in their detection. The majority of newer studies report an average radiation dose from 1 to 1.5 millisieverts. This study demonstrates a high sensitivity, specificity and positive predictive value in the detection of uroliths, however, its accuracy in the detection of alternative diagnoses is unknown. Therefore, we recommend using LD-CTKUB when the pre-test probability of stone disease is significantly higher than the pre-test probability of alternative diagnoses, such as follow-up of known calculi. We suggest caution when the pre-test probability of alternative diagnoses is high, such as the initial presentation of renal colic.