Impact of imaging modality choices on emergency department length of stay for patients with renal colic

ABSTRACT

Introduction & Objectives: Renal colic is a common presentation to emergency departments. Non-contrast CT is the gold standard for diagnosing ureteric stones. Ultrasound (USS) is also commonly used, however has lower sensitivity and specificity. Uncertainty in imaging findings can delay diagnosis and thereby prolong the length of stay (LoS) in the emergency department. The aim of this study was to assess the current imaging practices for assessment renal colic in the emergency department setting and the impact of imaging modality choices on patient flow. Methods: Patient presentations were identified from Emergency Department Information System for renal colic and urinary calculus diagnosis codes from October 2019 to September 2020. This was correlated with radiology departmental records for imaging modalities used. Clinical records were reviewed for demographics, LoS, disposition, imaging findings and radiation dose. Results: 590 presentations were identified, with 431 first presentations, 86 re-presentations (within 30 days) and 73 interhospital transfers. Imaging was performed in 74.7% of presentations (n = 441). Patients had a median age of 46 years and were mostly male (69%). 73.3% of first presentations had CT as first-line imaging. Those who had USS as first-line imaging were predominantly female (59%) and younger (mean 31.1 vs 46.6 years, p<0.01). They had longer total LOS when compared to CT for first presentations (mean 604 vs 443 minutes, p < 0.01) and all presentations (mean 599 vs 440 minutes, p<0.01). Compared to CT +/- abdominal x-ray, patients having USS were more likely to be admitted to the short stay unit (71.4% vs 43.7%) for longer periods (mean 511 vs 401 minutes, p = 0.05). 17% of patients who initially had USS subsequently had a CT, with this group having the longest mean LoS (total 713 minutes, short stay 720 minutes). Conclusions: USS is more likely to be used in younger and female patients. Compared to CT, first-line USS in renal colic correlated with longer time spent in ED, more admissions to short stay and longer LoS in short stay. Given constraints on hospital resources with the Covid-19 pandemic, renal colic imaging pathways should be examined for opportunities to improve patient flow.