Epidemiology of Acute Kidney Injury

The worldwide incidence of acute kidney injury (AKI) is increasing. Recent surveys demonstrated that AKI occurs in 21% of hospital admissions. In low-income countries, AKI has a bimodal presentation. In large urban centers, the pattern of AKI is very similar to that found in high and upper middle-income countries, with a predominance of hospital-acquired AKI, occurring mostly in older, critically ill, multiorgan failure patients with comorbidities. At the same time, in regional hospitals in small urban communities and rural areas, AKI is usually a community-acquired disease (related to diarrheal and infectious diseases, animal venom, and septic abortion). Although AKI mortality seems to be decreasing, it remains extremely high, varying from 23.9 to 60% in recent series. The most important risk factors for short-term mortality (in hospital or < 90 days) in AKI are the primary diagnosis (sepsis) and the severity of the acute illness, expressed by the presence of nonrenal organ dysfunction. New biomarkers, such as urinary neutrophil gelatinase-associated lipocalin, cystatin C, and interleukin-18 measurements, have been able to identify patients with AKI who are at risk for a less favorable prognosis, such as the likelihood of the need for renal replacement therapy, nonrecovery of kidney function, and higher mortality. Several studies have demonstrated an association between hospital-associated AKI and postdischarge mortality in a variety of contexts, and the most important risk factors for this late lethality are older age, preexisting comorbid disease (chronic kidney disease [CKD], cardiovascular disease, or malignancy), and incomplete organ recovery with ongoing residual disease. AKI is associated with de novo end-stage renal disease (ESRD) (CKD, progression of preexisting CKD) and the occurrence of ESRD in the long term. Herein, it is suggested that high-risk patients recovering from an AKI episode, such as those with baseline CKD, diabetes mellitus, or heart failure and those dialyzed for AKI, should likely be followed by a nephrologist.