Prognostic Biomarkers and AKI: Potential to Enhance the Identification of Post-Operative Patients at Risk of Loss of Renal Function

Abstract: Acute kidney injury (AKI) is a common complication after surgery and the more complex the surgery, the greater the risk. During surgery, patients are exposed to a combination of factors all of which are associated with the development of AKI. These include hypotension and hypovolaemia, sepsis, systemic inflammation, the use of nephrotoxic agents, tissue injury, the infusion of blood or blood products, ischaemia, oxidative stress and reperfusion injury. Given the risks of AKI, it would seem logical to conclude that early identification of patients at risk of AKI would translate into benefit. The conventional markers of AKI, namely serum creatinine and urine output are the mainstay of defining chronic kidney disease but are less suited to the acute phase. Such concerns are compounded in surgical patients given they often have significantly reduced mobility, suboptimal levels of nutrition and reduced muscle bulk. Many patients may also have misleadingly low serum creatinine and high urine output due to aggressive fluid resuscitation, particularly in intensive care units. Over the last two decades, considerable information has accrued with regard to the performance of what was termed "novel" biomarkers of AKI, and here, we discuss the most examined molecules and performance in surgical settings. We also discuss the application of biomarkers to guide patients' postoperative care. Plain Language Summary: Kidney damage is common after major surgery with a recent study showing almost 1 in 5 patients suffer kidney damage. The usual tests for measuring kidney function are excellent in the outpatient but not so good in acute scenario's. Therefore, there has been a lot of interest in new markers of kidney damage (so-called novel biomarkers) which perform well acutely and allow earlier detection of damage allowing treatment to be started earlier. This article summarises the currently available biomarkers for use post-operatively and points out the different information that can be achieved by using them routinely. Keywords: acute kidney injury, biomarkers, DKK-3, dickkopf-3, suPAR, soluble urokinase plasminogen activator receptor, IGFBP-7, insulin growth factor binding protein-7 and TIMP-2, tissue inhibitor of metalloproteinases-2, PENK, proenkephalin A 119-159, NGAL, neutrophil gelatinase-associated lipocalin, KIM-1, kidney injury molecule-1, CCL14, chemokine 14