Urine microscopy as a biomarker of Acute Kidney Injury following cardiac surgery with cardiopulmonary bypass

Abstract

Introduction: Acute kidney injury (AKI) occurs in about 22% of the patients undergoing cardiac surgery and 2.3% requires renal replacement therapy (RRT). The current diagnostic criteria for AKI by increased serum creatinine levels have limitations and new biomarkers are being tested. Urine sediment may be considered a biomarker and it can help to differentiate pre-renal (functional) from renal (intrinsic) AKI. Aims: To investigate the microscopic urinalysis in the AKI diagnosis in patients undergoing cardiac surgery with cardiopulmonary bypass. Methods: One hundred and fourteen patients, mean age 62.3 years, 67.5 % male, with creatinine 0.91 mg/dL (SD 0.22) had a urine sample examined in the first 24 h after the surgery. We looked for renal tubular epithelial cells (RTEC) and granular casts (GC) and associated the results with AKI development as defined by KDIGO criteria. Results: Twenty three patients (20.17 %) developed AKI according to the serum creatinine criterion and 76 (66.67 %) by the urine output criterion. Four patients required RRT. Mortality was 3.51 %. The use of urine creatinine criterion to predict AKI showed a sensitivity of 34.78 % and specificity of 86.81 %, positive likelihood ratio of 2.64 and negative likelihood ratio of 0.75, AUC-ROC of 0.584 (95%CI: 0.445-0.723). For the urine output criterion sensitivity was 23.68 % and specificity 92.11 %, AUC-ROC was 0.573 (95%CI: 0.465-0.680). Conclusion: RTEC and GC in urine sample detected by microscopy is a highly specific biomarker for early AKI diagnosis after cardiac surgery.

Alerting to acute kidney injury - Challenges, benefits, and strategies

“…While clinical laboratories are not typically involved in monitoring or measuring UO, the reduction in UO is an important criterion for diagnosis of AKI, and neglecting this marker could potentially delay AKI diagnosis or, even worse, miss it [ 50 ]. When there is UO, subsequent biochemical [ [53] , [54] , [55] ] or microscopic analysis [ 56 , 57 ] can be performed. However, non-oliguric AKI does not necessarily correlate with renal dysfunction as factors such as diuretics, vasodilators, or aggressive fluid resuscitation can contribute to urine flow [ 54 , 58 ].…”

Roflumilast improves resolution of sepsis‐induced acute kidney injury by retarding late phase renal interstitial immune cells infiltration and leakage in urinary sediments

“…A scoring system based on presence of granular casts (GC), renal tubular epithelial cells (RTECs) and lymphocytes, neutrophils, eosinophils, monocytes, basophils in urinary sediments was used to assess the renal infiltration, severity of injury and treatment effects (Table 1). Urinary microscopic analysis was performed, and rating was done according to the previously described scoring criteria with some modifications [34,35].…”

Cardiac Surgery-Associated Acute Kidney Injury in Children after Cardiopulmonary Bypass

“…It is not only a rise in SCr concentration that is associated with AKI, but there are other laboratory findings that are also correlated with kidney damage, which include renal tubular epithelial cells and granular casts, as well as mixed-cast detection by urine sediment microscopy (which allows for relatively easier and earlier kidney injury diagnostics). The findings of Goldani et al [26] show a specificity of 94.3% with only 22.8% sensitivity. Some researchers showed almost the same result with 89.9% specificity and 29.6% sensitivity [27], while another study did not reveal a significant diagnostic improvement by sediment microscopy [28].…”