Acute kidney injury (AKI) is a common, but significant complication after elective surgery which is associated with an increased risk of mortality, major adverse cardiac events, prolonged length of hospital stay, and increased cost per episode of care.

Acute kidney injury (AKI) is a common, but significant complication after elective surgery which is associated with an increased risk of mortality, major adverse cardiac events, prolonged length of hospital stay, and increased cost per episode of care. Obese patients are at increased risk of postoperative AKI when compared to normal weight patients; however current methods to assess preoperative renal function in this patient population (such as measurement of serum creatinine and calculation of the estimated glomerular filtration rate) have previously been demonstrated to overestimate their true renal function. , Preoperative proteinuria has previously been determined to be predictive of the development of postoperative AKI in patients of all weights undergoing cardiac surgery. Published reports on the prevalence of proteinuria in obese patients span a wide range: from 8- 43%. The investigators aim to determine the predictive value of preoperative proteinuria on the development of postoperative AKI in patients presenting for elective laparoscopic bariatric surgery at NYULMC. The investigators hypothesize that preoperative proteinuria will be associated with an increased incidence of AKI within 48 hours after elective laparoscopic bariatric surgery. Furthermore, since there is a wide range of reported prevalence of proteinuria in the bariatric patient population, part of the value of the study will be to provide a more definitive assessment of the prevalence of proteinuria in this surgical population.

Inclusion Criteria:

• ≥ 18 years of age
• Subjects undergoing elective laparoscopic bariatric surgery at NYULMC, including gastric banding, sleeve gastrectomy, and Roux -en-Y gastric bypass
• Surgery scheduled at least one day after Pre Admission Testing visit

Exclusion Criteria:

• Pre-existing end stage renal disease (CrCl <30ml/min and/or need for hemodialysis)
• Medical history of systemic disease known to cause proteinuria: monoclonal gammopathy, multiple myeloma, primary amyloidosis, diabetic nephropathy, acute myeloblastic leukemia, myoglobinuria, free hemoglobinuria (i.e intravascular hemolysis)
• Known pregnancy
• Diagnosis of AKI within 6 months of surgery
• Diagnosis of cognitive dysfunction (i.e. mental retardation/developmental delay, dementia, delirium)
• Any subject who the study team feels would be unable to comply with all protocol procedures.

Patients undergoing elective laparoscopic weight loss surgery including: gastric band placement, sleeve gastrectomy, gastric bypass, or a combination of the above procedures.