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Original Investigation
September 19, 2018

Association Between Preoperative Proteinuria and Postoperative Acute Kidney Injury and Readmission

Author Affiliations
  • 1Birmingham and Tuscaloosa Health Services Research and Development Unit, Birmingham Veterans Affairs Medical Center, Birmingham, Alabama
  • 2Department of Surgery, University of Alabama at Birmingham
  • 3Center for Healthcare Organization and Implementation Research, Veterans Affairs Boston Healthcare System, Boston, Massachusetts
  • 4Department of Surgery, Boston University School of Medicine, Boston, Massachusetts
  • 5School of Medicine, Harvard University, Boston, Massachusetts
  • 6Veterans Affairs Palo Alto Healthcare System, Palo Alto, California
  • 7Department of Surgery, Stanford University, Stanford, California
  • 8Milwaukee Veterans Affairs Medical Center, Milwaukee, Wisconsin
  • 9Department of Medicine, Medical College of Wisconsin, Milwaukee
  • 10Department of Surgery, Medical College of Wisconsin, Milwaukee
  • 11Veterans Affairs Central Western Massachusetts Health Care System, Leeds
  • 12Center for Applied Health Research, Baylor Scott and White Health, Temple, Texas
  • 13Department of Medicine, Texas A&M Health Science Center, Temple
JAMA Surg. 2018;153(9):e182009. doi:10.1001/jamasurg.2018.2009
Key Points

Question  What is the association between preoperative proteinuria and postoperative acute kidney injury and 30-day unplanned readmission among patients with and without known renal dysfunction at the time of surgery?

Findings  In this population-based study of 153 767 patients with and without known preoperative renal dysfunction, preoperative proteinuria was an indicator of probable postoperative acute kidney injury and 30-day unplanned readmission independent of preoperative renal dysfunction.

Meaning  Identification and early intervention of patients at risk for postoperative acute kidney injury through preoperative urinalysis assessments may improve patient outcomes.

Abstract

Importance  Proteinuria indicates renal dysfunction and is a risk factor for morbidity among medical patients, but less is understood among surgical populations. There is a paucity of studies investigating how preoperative proteinuria is associated with surgical outcomes, including postoperative acute kidney injury (AKI) and readmission.

Objective  To assess preoperative urine protein levels as a biomarker for adverse surgical outcomes.

Design, Setting, and Participants  A retrospective, population-based study was conducted in a cohort of patients with and without known preoperative renal dysfunction undergoing elective inpatient surgery performed at 119 Veterans Affairs facilities from October 1, 2007, to September 30, 2014. Data analysis was conducted from April 4 to December 1, 2016. Preoperative dialysis, septic, cardiac, ophthalmology, transplantation, and urologic cases were excluded.

Exposures  Preoperative proteinuria as assessed by urinalysis using the closest value within 6 months of surgery: negative (0 mg/dL), trace (15-29 mg/dL), 1+ (30-100 mg/dL), 2+ (101-300 mg/dL), 3+ (301-1000 mg/dL), and 4+ (>1000 mg/dL).

Main Outcomes and Measures  Primary outcome was postoperative predischarge AKI and 30-day postdischarge unplanned readmission. Secondary outcomes included any 30-day postoperative outcome.

Results  Of 346 676 surgeries, 153 767 met inclusion criteria, with the majority including orthopedic (37%), general (29%), and vascular procedures (14%). Evidence of proteinuria was shown in 43.8% of the population (trace: 20.6%, 1+: 16.0%, 2+: 5.5%, 3+: 1.6%) with 20.4%, 14.9%, 4.3%, and 0.9%, respectively, of the patients having a normal preoperative estimated glomerular filtration rate (eGFR). In unadjusted analysis, preoperative proteinuria was significantly associated with postoperative AKI (negative: 8.6%, trace: 12%, 1+: 14.5%, 2+: 21.2%, 3+: 27.6%; P < .001) and readmission (9.3%, 11.3%, 13.3%, 15.8%, 17.5%, respectively, P < .001). After adjustment, preoperative proteinuria was associated with postoperative AKI in a dose-dependent relationship (trace: odds ratio [OR], 1.2; 95% CI, 1.1-1.3, to 3+: OR, 2.0; 95% CI, 1.8-2.2) and 30-day unplanned readmission (trace: OR, 1.0; 95% CI, 1.0-1.1, to 3+: OR, 1.3; 95% CI, 1.1-1.4). Preoperative proteinuria was associated with AKI independent of eGFR.

Conclusions and Relevance  Proteinuria was associated with postoperative AKI and 30-day unplanned readmission independent of preoperative eGFR. Simple urine assessment for proteinuria may identify patients at higher risk of AKI and readmission to guide perioperative management.

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