Acute kidney injury, renal function, and the elderly obese surgical patient: a matched case-control study

Predictors of 30-day acute kidney injury following radical and partial nephrectomy for renal cell carcinoma

INTRODUCTION

Patients with renal cell carcinoma who were treated with radical nephrectomy (RN) or partial nephrectomy (PN) are at risk of postoperative acute kidney injury (AKI), and in consequence, short- and long-term adverse outcomes. We sought to identify independent predictors of 30-day AKI in patients undergoing RN or PN.

MATERIALS AND METHODS

Between 2005 and 2011, patients who underwent RN or PN for renal cell carcinoma within the National Surgical Quality Improvement Program data set were identified. Patients with preexisting severe renal failure, defined as a preoperative estimated glomerular filtration rate<30 ml/min/1.73 m(2), were excluded from the analyses. AKI was defined as an elevation of serum creatinine>2mg/dl above baseline or the need for dialysis within 30 days of surgery. Univariable and multivariable logistic regression analyses were used to examine the association between preoperative factors and the risk of postoperative AKI.

RESULTS

Overall, 1,944 (58.6%) and 1,376 (41.4%) patients underwent RN and PN, respectively. Overall, 1.8% of the patients included in the study experienced AKI within an average of 5.4 days after RN or PN. Independent predictors for AKI included obesity (odds ratio [OR] = 2.24, P = 0.04), history of neurovascular disease (OR = 5.29, P<0.001), and a preoperative chronic kidney disease stage II (OR = 10.00, P = 0.03) or stage III (OR = 26.49, P = 0.02). Furthermore, RN (OR = 2.87, P = 0.02) or the open approach (OR = 2.18, P = 0.04) was significantly associated with postoperative AKI. AKI was significantly associated with adverse postoperative outcomes, such as prolonged length of stay, occurrence of any complication, and mortality (all P <0.001).

CONCLUSIONS

The assessment of preoperative kidney function and comorbidity status is essential to identify patients at risk of postoperative AKI. In addition to preoperative chronic kidney disease stages II and III, neurovascular disease, obesity, and surgical approach (RN or open) represent predictors of 30-day AKI. Careful patient selection as well as preoperative planning may help reduce this unfavorable postoperative outcome.

The obesity paradox and acute kidney injury: beneficial effects of hyper-inflammation?

In the general population, obesity is associated with an increased mortality risk, whereas several epidemiological studies demonstrated a protective effect of obesity in critically ill patients. In this context, Sleeman and colleagues investigated the effects of obesity on kidney function in a well-established porcine model of cardiopulmonary bypass. The authors confirm literature data that obesity per se is associated with a chronic hyper-inflammatory status. Nevertheless, obese swine undergoing the surgical procedure presented with attenuated kidney dysfunction and tissue apoptosis. The authors suggest that the chronic inflammation causes pre-conditioning against excessive acute hyper-inflammation. The authors have to be commended for using a long-term, clinically relevant model that, moreover, addresses a variety of putative mechanisms. The study is discussed in the context of the controversial findings that, in contrast to the existing literature on improved survival, most studies available suggest a higher incidence and severity of acute kidney injury in obese patients when compared with lean controls.