The diagnostic yield of computed tomography in the management of acute flank pain and the emergency intervention rate for a proven acute ureteric stone.

INTRODUCTION: The diagnostic and management pathways for patients presenting with acute flank pain are complex. Although computed tomography (CT) of the kidneys, ureters and bladder (KUB) is the gold standard investigation for urolithiasis, the multitude of differential diagnoses must also be considered in the context of long-term risk from ionising radiation. This study investigated the integrated role and diagnostic yield of non-contrast CT in cases of acute flank pain.

METHODS: A retrospective cohort study was undertaken of 1,442 consecutive patients investigated with CT KUB between March 2013 and February 2015. The primary outcome was diagnostic yield of CT with secondary outcomes being predictors of need for urological intervention.

RESULTS: A cause for acute flank pain was identified in 717 patients (50%), there was an incidental finding in 389 patients (27%) and normal imaging was reported in 336 patients (23%). A diagnosis was more commonly made in male than in female patients (70% vs 40%) and with increasing age (46% in patients aged <30 years, 56% in those aged 30-49 years and 63% in those aged ≥50 years). The overall rate for an ipsilateral urinary tract stone was 41%. Factors strongly associated with emergency intervention included stone size >10mm (odds ratio [OR]: 11.7, 95% confidence interval [CI]: 3.3-42.7), stones located at the pelviureteric junction (OR: 7.8, 95% CI: 2.6-22.9), C-reactive protein >50mg/l and ≤100mg/l (OR: 15.2, 95% CI: 5.1-45.3), and estimated glomerular filtration rate ≤30ml/min (OR: 5.8, 95% CI: 1.5-21.8).

CONCLUSIONS: This contemporary study identifies age and sex as independent variables affecting the diagnostic yield of CT KUB in cases of acute flank pain, and highlights factors associated with a need for emergency intervention in proven ureteric stones.