title: Reply to Letter: "Causal Inference in Observational Studies in Surgery".
authors.affiliation: Department of General and Vascular Surgery Gundersen Health System La Crosse, WI Department of Surgery Research Gundersen Medical Foundation La Crosse, WI Department of General and Vascular Surgery Gundersen Health System La Crosse, WI snkothar@gundluth.org.
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Smith
authors.forename: Jacob G
authors.initials: JG
authors.lastname: Manske
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Mathiason
authors.forename: Kara J
authors.initials: KJ
authors.lastname: Kallies
authors.forename: Shanu N
authors.initials: SN
authors.lastname: Kothari
mesh_terms: D041881:Cholecystitis, Acute / Q000601:surgery*; D002767:Cholecystostomy / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male