## **LETTER** ![](https://assets.reachrx.ai/images/10.1007%E2%98%8Ds43678-025-01087-x/_page_0_Picture_2.jpeg) ## Re: The U-POCUS protocol: urinalysis and point-of-care ultrasound to exclude symptomatic ureterolithiasis in emergency department patients Paul Atkinson¹ • David Lewis¹ • Kavish Chandra¹ Received: 10 December 2025 / Accepted: 14 December 2025 © The Author(s), under exclusive licence to the Canadian Association of Emergency Physicians (CAEP)/ Association Canadienne de Médecine d'Urgence (ACMU) 2026 Dear Editor. We would like to congratulate Tripod and colleagues on a thoughtful analysis of a combined urinalysis and point-of-care ultrasound approach for symptomatic ureterolithiasis [1]. This work adds meaningfully to efforts to reduce unnecessary computed tomography in emergency departments. One aspect that warrants further discussion is how the proposed U-POCUS protocol interacts with the STONE score, which the authors use for estimating pre-test probability [2]. Hematuria is a weighted component of the STONE score, and it is also a defining component of a positive U-POCUS test. This introduces dependency between the pre-test and test variables, and may partly explain the very high sensitivity observed. In many cases, U-POCUS may effectively add only hydronephrosis as new information, raising the question of how often ultrasound meaningfully alters post-test probability when hematuria has already been incorporated upstream. The study reports a positive likelihood ratio of 1.2 and a negative likelihood ratio of 0.1 for the combined protocol. While the negative likelihood ratio supports a potential rule-out role in low-prevalence settings, the modest positive likelihood ratio limits its diagnostic precision. The very low specificity (14.8%) also raises concern about downstream consequences. In some systems, a high volume of positive screens could paradoxically increase computed tomography use, especially given variable operator experience with hydronephrosis on point-of-care ultrasound. These issues highlight the importance of distinguishing between screening and diagnostic use. Screening tools tolerate low specificity in favor of sensitivity; diagnostic tools require better balance. As Ransohoff and Feinstein noted, conflating these purposes can lead to misinterpretation and unintended diagnostic cascades [3]. Clarifying whether U-POCUS is primarily a screening pathway, a rule-out strategy or a diagnostic tool would help clinicians apply it more effectively. We commend the authors for advancing this conversation. Further clarification on how U-POCUS should be sequenced relative to STONE scoring, and the incremental value of hydronephrosis beyond urinalysis alone, would strengthen the protocol's practical applicability. Sincerely, Paul Atkinson, David Lewis, and Kavish Chandra. ## **Declarations** Conflict of interest The authors declare that there are no conflicts of inter- ## References - 1. Tripod M, Mendez K, Berger M, et al. The U-POCUS protocol: urinalysis and point-of-care ultrasound to exclude symptomatic ureterolithiasis in emergency department patients. Can J Emerg Med. 2025;27:1002-9. https://doi.org/10.1007/ s43678-025-00998-z. - 2. Malik A, Mohkumuddin S, Yousaf S, Baig MAR, Afzal A. Validity of STONE Score in Clinical Prediction of Ureteral Stone Disease. Pak J Med Sci. 2020;36(7):1693–1697. https://doi.org/10. 12669/pjms.36.7.2625 - 3. Ransohoff DF, Feinstein AR. Problems of spectrum and bias in evaluating the efficacy of diagnostic tests. N Engl J Med. 1978;299:926-30. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Published online: 12 January 2026 ![](https://assets.reachrx.ai/images/10.1007%E2%98%8Ds43678-025-01087-x/_page_0_Picture_24.jpeg) ![](https://assets.reachrx.ai/images/10.1007%E2%98%8Ds43678-025-01087-x/_page_0_Picture_25.jpeg) Paul Atkinson paul.atkinson@dal.ca Department of Emergency Medicine, Dalhousie Medicine New Brunswick, Saint John, NB, Canada