In the past decade, acute kidney injury (AKI) has emerged as a syndrome of increasing prevalence. Since 2005, hospital-diagnosed cases of AKI have outnumbered those of chronic kidney disease (CKD), and this trend has continued to climb. Patients diagnosed with AKI are at risk for a variety of adverse outcomes, including premature death, morbidity, prolonged hospitalization, and increased medical costs. Potential contributing factors to the development of AKI include pre-existing kidney damage, hemodynamic instability, and the complexity of concurrent medications. As modern medical diagnostic and treatment tools have advanced, the incidence and prevalence of AKI have been steadily rising.

The KDIGO Guideline for AKI recommended that we should diagnose AKI if a given patient has a 6 hour urine amount less than 0.5ml/kg/hr or a serum creatinine elevates more than 0.3mg/dL or 1.5 times greater than baselines. Epidemiology data on hospitalized patients indeed disclosed high risk for adverse events using this classification system and its analogues. However, besides diagnosis, we do not have a useful tool to treat or to help improve patient outcomes Acute kidney injury (AKI) is a common complication that affects nearly 5% of hospitalized patients and 40%-70% of patients in the intensive care unit. AKI requiring dialysis (AKI-D), the most severe type of AKI, is associated with the highest proportion of morbidity and mortality. AKI is associated with a risk of end-stage renal disease (ESRD) that is 13 times as high as the risk among patients without AKI, and the risk of ESRD is 40 times as high if the patients have both AKI and pre-existing chronic kidney disease (CKD). Since AKI is recognized as a risk factor for the development of ESRD, it is crucial to have appropriate protection strategies for the avoidance of further target organ damage and associated mortality in the critical phases of the acute kidney disease (AKD). Patients with Acute Kidney Injury (AKI) requiring dialysis (AKI-D) are associated with the highest proportion of morbidity and mortality. AKI is associated with a thirteen-fold higher risk of end-stage renal disease (ESRD) compared to those without AKI, and a forty-fold higher risk if the patient has both AKI and pre-existing chronic kidney disease (CKD). Given the potential for AKI to lead to ESRD, it is essential to develop strategies to protect the target organs from further damage and associated mortality during the acute phase of AKD. Guyton proposed that the kidneys have a crucial role in determining the chronic level of blood pressure (BP), and studies have validated this hypothesis. Furthermore, hospitalization-associated AKI has been identified as an independent risk factor for the development of elevated BP. Elevated BP is a leading risk factor for global health and cardiovascular disease, making it a key element in the pharmacologic treatment and long-term protection of AKD patients. A retrospective analysis of the ICU database, which included 1551 ICU survivors, 611 of which had AKI during their stay, demonstrated a reduced 1-year mortality in those who had AKI and had been prescribed ACEIs/ARBs.

To address the gap between acute kidney injury (AKI) and chronic kidney disease (CKD), the Kidney Disease: Improving Global Outcomes (KDIGO) AKI Workgroup has proposed the concept of acute kidney disease (AKD). AKD is defined as a glomerular filtration rate (GFR) of less than 60 ml/min/1.73 m2 or evidence of structural kidney damage that has been present for less than 3 months. This concept provides an integrated bridge between AKI and CKD and also emphasizes the concept of partial renal recovery. It may help to raise awareness and create the necessary clinical mechanisms to follow up AKI survivors for the potential progression to CKD, which has been recently highlighted as a missed opportunity for adequate transitions of care. Furthermore, a panel of gut microbiota and biomarkers will be determined.