LAUSR

INTRODUCTION Infected ureteral stones are a urologic emergency and require urgent decompression. We set out to determine if serum procalcitonin could aid in the diagnosis of infected ureteral stones. METHODS All consecutive patients presenting to the emergency room from 11/9/2016 to 11/10/2018 with an obstructing ureteral stone were included. All patients had complete blood count (CBC), urinalysis (UA), procalcitonin (PCT) and urine culture (UCx). Subgroup analysis was performed in a "clinically equivocal" cohort of afebrile patients defined as a leukocytosis >10^4/l and UA with <50 WBCs/high powered field (hpf). Patients with positive and negative UCx were compared. RESULTS 231 patients were included, of which 56 had a positive UCx. Of all covariates, UA WBC with a cutoff of 9 per hpf performed best at predicting positive UCx with an area under the curve (AUC) of 0.87. PCT did not perform as well with an ideal cutoff of 0.08 ng/ml having an AUC of 0.77, sensitivity 70.6%, specificity, 73.9%, positive predictive value (PPV) 34.3%, negative predictive value (NPV) 92.9%. When looking at the clinically equivocal cohort, UA WBC with a cutoff of 6 per hpf appeared to perform best at predicting a positive UCx with an AUC of 0.72. PCT was less predictive in this cohort with an ideal cutoff of 0.3 ng/ml having an AUC of 0.32, sensitivity 47.1%, specificity 85.2%, PPV 38.1%, and NPV 89.3%. CONCLUSION PCT does not appear to be a superior marker for diagnosing UTI in the setting of obstructing ureterolithiasis when compared to components of the standard workup.