The GFR was the primary outcome measure. It was calculated
using the Modification of Diet in Renal Disease (MDRD) equation8
: GFR (mL/min/1.73 m2
) ¼ 175 (serum creatinine)
1.154 (age) 0.203 (0.742, if female). To be consistent with
previous studies, decreased renal function was defined as a reduction
in the GFR > 1 mL/min/1.73 m2 annually after surgery.4,5,9,10 To
evaluate the factors associated with an eGFR decrease, we compared
the preoperative values with those obtained at the subsequent
postoperative visits. The CKD stage was also used to classify renal
function.11 Similar to a recent analysis,5 we compared the preoperative
eGFR with the values obtained at the subsequent postoperative
visits. At the 1-year postoperative point, we evaluated
serum creatinine, measured 9 to 18 months postoperatively. In
addition, we accounted for all subsequent values obtained within
6 months of the following years. The median serum creatinine
values were calculated if multiple values were available for a given
measurement point