The following is a summary of “CT Use Reduction In Ostensive Ureteral Stone (CURIOUS),” published in the May 2023 issue of Emergency Medicine by Durant, et al.

Computed tomography (CT) is a standard imaging modality used in patients diagnosed with ureteral stones. However, only a small percentage of patients presenting to the emergency department (ED) with acute flank pain are hospitalized for clinically significant stones or other diagnoses. Hydronephrosis, the swelling of the kidney due to obstruction, can be accurately detected using point-of-care ultrasound and is a key predictor of ureteral stones and the risk of complications. However, the absence of hydronephrosis does not exclude the presence of a stone. For a study, researchers sought to develop a sensitive clinical decision rule to identify patients at low risk for clinically significant ureteral stones.

The retrospective cohort study included a random sample of 4,000 adults who presented to 21 Kaiser Permanente Northern California EDs and underwent CT for suspected ureteral stones between January 1, 2016, and December 31, 2020. The primary outcome was a clinically significant stone, defined as a stone that resulted in hospitalization or a urologic procedure within 60 days. Recursive partition analysis was used to develop a clinical decision rule to predict the outcome. The C-statistic (area under the curve) was calculated, and a receiver operating characteristic (ROC) curve was plotted for the model. The model’s sensitivity, specificity, and predictive values were also calculated using a risk threshold of 2%.

Among the 4,000 patients, 354 (8.9%) had a clinically significant stone. The partition model generated four terminal nodes with risk levels ranging from 0.4% to 21.8%. The area under the ROC curve was 0.81 (95% CI 0.80, 0.83). Using a risk cut point of 2%, a clinical decision tree incorporating hydronephrosis, hematuria, and a history of prior stones predicted complicated stones with a sensitivity of 95.5% (95% CI 92.8%–97.4%), specificity of 59.9% (95% CI 58.3%–61.5%), positive predictive value of 18.8% (95% CI 18.1%–19.5%), and negative predictive value of 99.3% (95% CI 98.8%–99.6%).

Implementing the clinical decision rule for imaging decisions could have resulted in 63% fewer CT scans with a miss rate of 0.4%. A limitation of the study was that the decision rule was applied only to patients who underwent CT for suspected ureteral stones. Therefore, the rule may not apply to patients suspected of having ureteral colic but did not undergo CT due to a diagnosis based on ultrasound or history. Prospective validation studies were needed to evaluate the usefulness of this decision rule further.

Source: sciencedirect.com/science/article/abs/pii/S0735675723000943