2.2 Outcome

The primary outcome was the daily count of kidney stone presentations in South Carolina. A kidney stone presentation was defined as emergency department, inpatient, or surgical care associated with primary international classification of diseases, 9^th revision codes for nephrolithiasis (592.0, 592.1, 592.9, 274.11). These criteria capture clinically important acute stone events because of the painful nature of stone episodes that require emergency evaluation, hospital admission, and/or surgery (Bush et al., 2010; Ghani et al., 2014). The first qualifying claim defined the date of presentation. Kidney stone presentations among unique individuals were limited to the earliest occurrence.