The U-POCUS protocol: urinalysis and point-of-care ultrasound to exclude symptomatic ureterolithiasis in emergency department patients

Urolithiasis is a common urological condition accounting for more than 1.3 million emergency department visits annually with costs exceeding $2.8 billion (Scales et al. in Eur Urol. 62:160-5, 2012;Eaton et al. in J Endourol 27:1535-1538, 2013;Antonelli et al. in Eur Urol 66:724-729, 2014;). Non-contrast computed tomography of the abdomen and pelvis remains the diagnostic gold standard. Studies assessing urinalysis and renal point-of-care ultrasound (PoCUS), individually, to diagnose symptomatic ureterolithiasis demonstrate inadequate sensitivities (Mefford et al. in West J Emerg Med 18:775, 2017;Eray et al. in Am J Emerg Med 21:152-4, 2003;Luchs et al. in Urology 59:839-842, 2002;Smith-Bindman et al. in N Engl J Med 371:1100-1110, 2014;Riddell et al. in West J Emerg Med 15:96-100, 2014;Rosen et al. in J Emerg Med 16:865-870, 1998;Gaspari and Horst in Acad Emerg Med 12:1180-1184, 2005;Watkins et al. in Emerg Med Australas 19:188-195, 2007;). The primary objective of this study was to assess the test characteristics of the U-PoCUS (urinalysis with renal point-of-care ultrasound) protocol. This was an Institutional Review Board approved, multi-center, retrospective chart review at a university-based healthcare system. Study investigators included all patients who presented from January 1, 2016 through June 30, 2020, and underwent computed tomography of the abdomen and pelvis and had a urinalysis and PoCUS for suspected ureterolithiasis. Investigators utilized MedCalc (Version 19.1.6) and standard 2 × 2 tables to calculate test characteristics with 95% confidence intervals (CI). Study investigators enrolled 183 patients, including 122 patients diagnosed with computed tomography confirmed ureterolithiasis and 61 patients without it. The combination of hematuria and/or hydronephrosis on PoCUS had a sensitivity of 99.2% (95.6-100) and a specificity of 14.8% (7-26.2) for the presence of urolithiasis. Positive predictive value and negative predictive value were 69.9% (67.7-72.1) and 90% (53.9-98.6), respectively. The presence of hematuria and/or hydronephrosis was 99.2% sensitive for the presence of ureterolithiasis diagnosed on computed tomography of the abdomen and pelvis. The U-PoCUS protocol missed only one symptomatic ureterolithiasis.