Acute kidney injury (AKI) adversely affects long-term functional recovery following partial nephrectomy (PN) for renal masses, according to a new study.

Carlo Andrea Bravi, MD, of IRCCS Ospedale San Raffaele in Milan, Italy, and colleagues studied 1893 patients who underwent PN for cT1 N0 M0 renal masses. Of these, 388 (20%) experienced postoperative AKI, as defined by RIFLE criteria. After 1-year follow-up, these patients had a significantly lower rate of recovering 90% of baseline estimated glomerular filtration rate (eGFR) after PN than those who did not experience AKI (30% vs 61%), Dr Bravi’s team reported in European Urology. The AKI group also had a significantly higher proportion of patients who had chronic kidney disease (CKD) upstaging (51% vs 23%). The eGFR at 1 year was significantly lower in the AKI than no-AKI group (60 vs 71 mL/min/1.73 m2). In addition, compared with baseline, the AKI group experienced a 17% decrease in eGFR, whereas the patients with no AKI had a 1% decrease, significant difference between the groups.

On multivariable analysis, AKI was associated with worse renal function 1 year after PN. The risk of CKD stage upgrading for an average patient who had 1–3 vs 4 or more days of AKI was 46% vs 67%, corresponding to an absolute risk increase of 21%, according to the investigators.

Compared with patients who had no AKI, those with AKI for 1, 2–3, and 4 or more days had a significant 60%, 70%, and 92% decreased likelihood of recovering 90% of baseline eGFR, respectively, and 2.3-, 3.1-, and 6.2-fold increased risk of CKD upstaging.

The investigators said they are confident about their results because of the large sample size, high number of events, and multiple end points, and noted that their finding of a negative effect of AKI on long-term renal function is biologically plausible.

“Our findings have important implications for clinical practice. First, efforts should be made to avoid AKI during partial nephrectomy,” the authors wrote. “Predictors of AKI have been identified, and thus, patients at risk should receive proper interventions for modifiable determinants of AKI (ie, ischemia time and preoperative correction of medical conditions).”

Dr Bravi and colleagues also noted that the association between the duration of AKI and long-term damage has relevant implications for postoperative follow-up. If replicated, they observed, their data support inclusion of AKI duration into classification systems, discriminating transient from persistent AKI.

“This distinction seems compelling when AKI is a one-time event such as after surgical operations, thereby improving postoperative stratification according to individual risk of functional deterioration.”

In a discussion of study limitations, the authors noted that did not have data on urine output, a component of the current AKI classification criteria. “Still,” they noted, “we are confident that the definition of AKI using other clinical parameters included in the RIFLE criteria remain sound.”

The authors also acknowledged the possibility of some ascertainment bias toward longer AKI. For example, if a patient experienced AKI on postoperative day 1, they are more likely to receive blood examinations in the following days, with a consequent higher probability of ascertaining longer injury, Dr Bravi and colleagues wrote.

Reference

Bravi CA, Vertosick E, Benfante N, et al. Impact of acute kidney injury and its duration on long-term renal function after partial nephrectomy. Eur Urol. 2019.

https://www.europeanurology.com/article/S0302-2838(19)30356-2/fulltext