INTRODUCTION, DEFINITIONS, AND EPIDEMIOLOGY
Although pregnancy-related renal failure has become a rare occurrence in developed countries, it still remains a challenge in the clinical setting and is associated with mortality and significant long-term morbidity. Original definitions of renal failure ranging from serum creatinine (sCr) levels of >0.8 mg/dL to dialysis have rendered comparison of epidemiologic studies difficult.1,2,3,4,5
With the introduction of the Risk, Injury, Failure, Loss, and End-stage Kidney (RIFLE) Consensus Classification for Acute Kidney Injury (RIFLE-AKI), there is now a standard description from mild to severe forms of AKI. The adverse effects of small changes in sCr have been recognized and systematically studied.2,6,7 Hence, the term AKI replaces the old term, “acute renal failure (ARF),” to encompass the entire spectrum of the syndrome, from minor changes in renal function to the requirement for dialysis.7 The RIFLE classification defines three grades of AKI severity (R—Risk, I—Injury, F—Failure) based on at least a 50% change in sCr relative to the reference sCr3,8,10 (Figure 15-1). The most recent international consensus conference expanded the RIFLE criteria to include changes as small as 0.3 mg/dL, further recognizing the negative impact of even smaller changes in sCr on short- and long-term outcomes in different patient populations.10
RIFLE criteria for acute kidney injury.
The incidence of pregnancy-related kidney injury has decreased from 1/3000 to 1/15,000.9 Although there has been a decline in reported pregnancy-related kidney injury, there has been little change in overall mortality and morbidity. This is likely secondary to the fact that patients that develop kidney injury are likely to have multiorgan dysfunction along with a more severe pathogenesis of disease. Associated mortality with AKI with subsequent kidney failure ranges from 0% to 30%; however, there is usually a full renal recovery in survivors of 60% to 90%.10,11,12,13 Historically, there was a bimodal incidence of renal failure in pregnancy. There was a peak in the first trimester related to the high rates of septic abortions, and then a second peak in the third trimester of pregnancy, likely related to hypertensive diseases of pregnancy. Therefore, the major decrease in pregnancy-related kidney injury is related to the legalization of abortion and an increase in surveillance for preeclampsia and other obstetric complications in the third trimester of pregnancy.10,11 Although it is anticipated that many reproductive aged women will have normal renal function, it is well known that in women with underlying chronic renal dysfunction (baseline sCr >1.4), there is a significant increased risk of renal loss (43%), and 10% of patients will experience a rapid deterioration of renal function.
ETIOLOGY, CLINICAL PRESENTATION, AND DIAGNOSIS OF ACUTE KIDNEY INJURY