Early Identification of Acute Kidney Injury after Bariatric Surgery: Role of NGAL and Cystatin C

Sidoti Anna1, *, Giacalone Marilu1, Abramo Antonio1, Anselmino Marco2, Carlo Donadio3, laudio Di Salvo4, Giunta Francesco1, Forfori Francesco1
1 Dipartimento di Anestesia e Rianimazione Università di Pisa, Via Paradisa 2, Pisa (PI), Tuscany, Italy
2 Sezione Dipartimentale Chirurgia Bariatrica, University of Pisa, Via Paradisa 2, Pisa (PI), Tuscany, Italy
3 UO Nefrologia, University of Pisa, Via Paradisa 2, Pisa (PI), Tuscany, Italy
4 Sezione di Anestesia e Rianimazione in Chirurgia dell'obesità e delle patologie delle vie digestive superiori: Nuovo S.Chiara Hospital, AOUP, University of Pisa, Via Paradisa 2, Pisa (PI), Tuscany, Italy

© 2014 Sidoti et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Dipartimento di Anestesia e Rianimazione Università di Pisa; Italy; Tel: +39050997608; Fax: +39050997607; E-mail:



The aim of our study was to evaluate plasmatic and urinary NGAL and serum cystatin C as early diagnostic markers of acute kidney injury in obese patients undergoing bariatric surgery.


For this this prospective observational study, we recruited 23 patients undergoing gastric by-pass or sleeve gastrectomy, and admitted to the Low Dependence Unit after the surgery. Plasma NGAL (pNGAL), urinary NGAL (uNGAL), serum cystatin C, serum creatinine, and serum urea were measured before surgery as well as 10 h and 24 h after surgery.

Mean values of pNGAL, uNGAL, cystatin C, creatinine, and urea concentrations of pre- and post-surgery periods were compared using Student’s t test for paired data. We also evaluated the presence of correlation between modifications of NGAL and cystatin C after surgery and fluid balance, hydration (ml/kg) and diuresis using Pearson’s coefficient of correlation.


No patient developed AKI according to the AKIN criteria. pNGAL was significantly higher at T10h than T0 (p=0.004). There was no significant difference between uNGAL at T0 and T10h (p=0.53) and between uNGAL at T0 and T24h (p=0.31). uNGAL at T was significantly higher in comparison to T10h (p=0.024). uNGAL concentrations were normal in all patients at every time step.

Cystatin C concentration did not increase after surgery.

Serum creatinine level was significantly higher at T48h, despite being still within the normal range, when compared to T0 (p=0.038).


Our study shows that pNGAL can reflect mild tubular damage as its levels increase within a few hours from surgery and return to normal limits afterwards. Concerning uNGAL, there is a minimal increase at T24h, when NGAL concentration in plasma has already decreased. Serum cystatin C does not show any relevant kidney changes, or at least, no more than those ones shown by pNGAL.

Keywords: Morbid obese patients, bariatric surgery, acute kidney injury, plasmatic and urinary neutrophil gelatinaseassociated lipocalin (NGAL), cystatin C.