A 68-year-old white man was admitted in May 2015 with dysuria and low-back pain. He had a history of coronary artery disease and obesity, for which he underwent Roux-en-Y gastric bypass (RYGB) in 1998. On presentation, serum creatinine level was 6.5mg/dL, corresponding to an estimated glomerular filtration rate (eGFR) of 9mL/min/1.73m2, as calculated by the 4-variable MDRD (Modification of Diet in Renal Disease) Study equation. The patient’s baseline creatinine level of 1.4mg/dL (eGFR, 50mL/min/1.73m2) had increased to 3.3mg/dL (eGFR, 19mL/min/1.73m2) in October 2014 and 5mg/dL (eGFR, 10.8mL/min/1.73m2) in March 2015.