Optimizing imaging choices for renal colic in the emergency department: Insights from a pilot study at Hatta Hospital, UAE

ABSTRACT: Introduction: Patients presenting to the emergency department with flank pain and hematuria often require abdominal imaging to evaluate for kidney stones. The choice of imaging modality—plain KUB film, abdominal ultrasound (USG), or non-contrast CT—remains a critical decision for emergency physicians due to differences in sensitivity and specificity. Objective: The main objective of this study is to evaluate the diagnostic accuracy and efficiency of different imaging modalitiesnon-contrast CT KUB, abdominal ultrasound (USG), and plain KUB film—in detecting kidney stones among patients presenting with renal colic in the emergency department. The study seeks to provide evidence-based insights for optimizing imaging protocols, with a focus on balancing diagnostic precision, time to diagnosis, and minimizing radiation exposure, particularly for younger patients. Methods: This retrospective pilot study was conducted from January 2024 to October 2024 at Hatta Hospital, encompassing 305 patients across various age groups who presented with flank pain and hematuria. Patients were categorized based on the imaging modality utilized: non-contrast CT KUB (n=150), USG abdomen (n=100), and plain KUB film (n=55). Sensitivity and specificity for each modality were calculated using standard formulas, with non-contrast CT KUB demonstrating a sensitivity of 95% and specificity of 93% for detecting kidney stones, compared to 80% sensitivity and 75% specificity for USG abdomen, and 60% sensitivity and 55% specificity for plain KUB film (p < 0.01). Discussion: This pilot study offers a comparative analysis of the diagnostic performance and operational efficiency of non-contrast computed tomography of the kidneys, ureters, and bladder (CT KUB), abdominal ultrasound (USG), and plain kidney-ureter-bladder (KUB) radiography in the emergency evaluation of renal colic. Our findings reinforce the position of non-contrast CT KUB as the gold standard in the diagnostic workup of suspected nephrolithiasis, while also highlighting important considerations for balancing diagnostic accuracy, patient safety, and resource utilization. The diagnostic superiority of CT KUB in our cohort was evident, with a sensitivity and specificity of 95% and 93%, respectively. This is consistent with established international data demonstrating CT’s high reliability in detecting urinary calculi regardless of size or location. Moreover, CT KUB yielded the shortest mean time to diagnosis (30 minutes), likely due to its comprehensive anatomic detail and rapid acquisition capabilities, which support timely clinical decision-making and intervention—particularly crucial in settings where complications such as obstructive uropathy or infection are of concern. In contrast, abdominal ultrasound demonstrated moderate sensitivity (80%) and specificity (75%) in our study. Although operator-dependent and limited in its ability to visualize distal ureteric or small non-obstructive stones, USG remains a valuable first-line modality, particularly in specific subgroups. It is especially appropriate for younger patients, pregnant women, or those with recurrent stone disease, where minimizing cumulative radiation exposure is a clinical priority. Plain KUB radiography, with the lowest diagnostic accuracy (sensitivity 60%, specificity 55%), was found to have limited utility as a standalone imaging tool. Its diagnostic limitations stem from its inability to detect radiolucent stones and overlapping bowel gas that can obscure visibility. However, KUB may retain a role in follow-up of known radiopaque calculi or as a supplementary modality in resource-limited environments. Given the statistically significant differences in diagnostic outcomes across the three modalities (p < 0.01), it is imperative that imaging selection is tailored to both clinical context and patient characteristics. In terms of workflow efficiency, our findings further emphasize the value of CT in reducing diagnostic delays and expediting definitive management. This has implications for emergency department throughput and patient satisfaction, though it must be balanced against concerns of overutilization and potential overdiagnosis, especially of incidental findings that may lead to unnecessary interventions. The results of this study support the need for institution-specific imaging algorithms that integrate patient age, clinical presentation, risk stratification, and availability of imaging modalities. Decision-support tools, such as clinical prediction rules and point-of-care ultrasound protocols, may aid in reducing unnecessary CT utilization without compromising diagnostic accuracy or patient outcomes. Results: Among the 150 patients who underwent non-contrast CT KUB, 120 (80%) were confirmed to have kidney stones. In contrast, 50 (50%) of those who underwent USG abdomen and 20 (36.4%) of those who had plain KUB film were confirmed to have stones (p < 0.001). The average time to diagnosis was significantly shorter for non-contrast CT KUB (mean 30 minutes) compared to USG abdomen (mean 45 minutes) and plain KUB film (mean 60 minutes) (p < 0.05). Conclusions: Non-contrast CT KUB is the preferred imaging modality for all age groups exhibiting signs of typical renal colic, given its high sensitivity (95%) and specificity (93%). USG abdomen is recommended for younger patients to minimize radiation exposure while maintaining reasonable diagnostic efficacy. Although plain KUB film can be utilized in cases without severe renal colic symptoms, it demonstrates significantly lower sensitivity (60%) and specificity (55%) (p < 0.01). These findings underscore the importance of protocol standardization in imaging for renal colic within emergency settings. Keywords: pain and hematuria, abdominal ultrasound (USG), renal colic