The accuracy of urinary ultrasound in the diagnosis of urinary stone disease in patients with acute flank pain: is it influenced by the time of ultrasound performance during the day or week?

BACKGROUND: The aim of this article is to investigate the possible impact of timing of ultrasound (US) during the day or week on its diagnostic accuracy. METHODS: We analyzed the records of 500 patients who underwent an initial urinary US, followed by a noncontrast computed tomography (NCCT) for the assessment of urinary stone disease. The sensitivity, specificity, negative and positive predictive values, negative and positive likelihood ratio, and overall diagnostic accuracy rates of US and were analyzed at different times of the day or week. RESULTS: The specificity and diagnostic accuracy of urinary US showed a decline toward the middle of the week followed by a steady rise by the end of the week, higher sensitivity for urinary US was noticed around mid-week. On the other hand, when urinary US results are subgrouped according to the time of the day they are performed, the specificity remained generally stable but the sensitivity and diagnostic accuracy showed lowest levels between 11:00 a.m. and 02:00 p.m. and between 04:00 p.m. and 05:00 p.m. Although some observational differences between sensitivity, specificity, and diagnostic accuracy of urinary US performed at different times of the day or week are seen, these differences were not statistically significant. CONCLUSIONS: Our study showed no significant influence of US timing on its diagnostic accuracy. A larger randomized prospective series is necessary to evaluate the impact of different factors on "precision" and "accuracy" in US reporting and, hence, the diagnostic accuracy of urinary US in identifying urinary stone disease.