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. Author manuscript; available in PMC: 2016 Apr 1.
Published in final edited form as: J Am Coll Surg. 2014 Dec 17;220(4):682–690. doi: 10.1016/j.jamcollsurg.2014.12.012

Figure 1.

Figure 1

Cohort selection. Inclusion criteria: 1) Symptomatic cholelithiasis defined by a) Primary diagnosis of ICD-9-CM code 574 of 575 or b) Primary diagnosis of acute pancreatitis (577.0) and a secondary diagnosis of 574 or 575; 2) Patients age 66 and older; 3) Patients with Medicare Part A and Part B 1 year before and 2 years after the initial episode; 4) Patients not admitted to the hospital on the incident episode; and 5) Patients who underwent CT and/or US in the month before or after diagnosis were included. US, ultrasound.