Association Between Preoperative Proteinuria and Postoperative Acute Kidney Injury and Readmission

Abstract

<div class="section"> <a class="named-anchor" id="ab-soi180035-1"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e571">Question</h5> <p id="d9130567e573">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? </p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-2"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e576">Findings</h5> <p id="d9130567e578">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. </p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-3"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e581">Meaning</h5> <p id="d9130567e583">Identification and early intervention of patients at risk for postoperative acute kidney injury through preoperative urinalysis assessments may improve patient outcomes. </p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-4"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e588">Importance</h5> <p id="d9130567e590">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. </p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-5"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e593">Objective</h5> <p id="d9130567e595">To assess preoperative urine protein levels as a biomarker for adverse surgical outcomes.</p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-6"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e598">Design, Setting, and Participants</h5> <p id="d9130567e600">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. </p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-7"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e603">Exposures</h5> <p id="d9130567e605">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+ (&gt;1000 mg/dL). </p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-8"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e608">Main Outcomes and Measures</h5> <p id="d9130567e610">Primary outcome was postoperative predischarge AKI and 30-day postdischarge unplanned readmission. Secondary outcomes included any 30-day postoperative outcome. </p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-9"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e613">Results</h5> <p id="d9130567e615">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%; <i>P</i> &lt; .001) and readmission (9.3%, 11.3%, 13.3%, 15.8%, 17.5%, respectively, <i>P</i> &lt; .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. </p> </div><div class="section"> <a class="named-anchor" id="ab-soi180035-10"> <!-- named anchor --> </a> <h5 class="section-title" id="d9130567e624">Conclusions and Relevance</h5> <p id="d9130567e626">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. </p> </div><p class="first" id="d9130567e629">This population-based study examines the outcomes of acute kidney injury and readmission in patients with preoperative proteinuria. </p>