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Introduction: Renal colic is among the most painful conditions that patients experience. The main outcome determinants for patients with renal colic are stone size, location and hydronephrosis; however, little is known about the association of pain with these parameters. Our objective was to determine whether more severe pain is associated with larger stones, more proximal stones or more severe hydronephrosis, findings that might suggest the need for advanced imaging, hospitalization or early intervention. Methods: We used administrative data and structured chart review to study all adult emergency department (ED) patients in two cities with a renal colic diagnosis over one-year. Patients with missing imaging results or pain scores were excluded. Triage nurses recorded numeric rating scale (NRS) pain scores on arrival. We stratified patients into mild (NRS <4), moderate (NRS 4-7) and severe (NRS 8-10) pain groups, as per CTAS guidelines. Stone size (mm) and location (proximal, middle, distal ureter, or renal) were abstracted from imaging reports, while index admissions were determined from hospital discharge abstracts. We used multivariable linear regression to determine the association of arrival pain with stone characteristics and hydronephrosis severity (primary outcome), and we used multivariable logistic regression to determine the association of pain with index hospitalization (secondary outcome). We also performed a stratified analysis looking at ureteral vs. kidney (intrarenal) stones. Results: We studied 1053 patients, 66% male, with a mean age of 48 years. After controlling for patient and disease characteristics, we found no significant association between pain severity and stone size (b=−0.0004; 95%CI = -0.0015, 0.0008) or stone location (b = 0.0045; 95%CI: -0.020, 0.029). Nor did we find an association between pain and hydronephrosis severity (b = 0.016; 95%CI: -0.053, 0.022, p = 0.418). Stratified analyses using a Bonferroni correction for multiple comparisons revealed the same absence of associations in the kidney and ureteral stone subgroups. Arrival pain did not predict index admission (OR = 0.82, 95% CI: 0.59, 1.16). Conclusion: Arrival pain scores are not associated with stone size, stone location or hydronephrosis severity, and do not predict index visit hospitalization in ED patients with renal colic. Severe pain should motivate efforts to minimize treatment delays, but do not suggest the need to modify advanced imaging or admission decisions.
