Subclinical renal injury in obesity following bariatric surgery: insights from a prospective cohort.

BACKGOUND: The effects of bariatric surgery on kidney function remain controversial. This study aims to assess changes in kidney function, with a specific focus on structural biomarkers, in individuals with obesity but without evident kidney disease following bariatric surgery.

METHODS

Fifty-two patients with obesity and an estimated glomerular filtration rate from creatinine and cystatin C (eGFRcr-cyc) of at least 90 mL/min/1.73 m2 underwent sleeve gastrectomy (SG). Serum levels of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) were measured at baseline, one month, and one year postoperatively to assess structural injury.

RESULTS

eGFRcr-cyc decreased one month postoperatively (117.4 [103.2,133.2] to 105.8 [97.0,122.7] mL/min/1.73 m2), but restored to near baseline levels by one year (112.2 [107.2,122.4] mL/min/1.73 m2). KIM-1 levels showed no significant change at one month (53.4 [35.6,73.9] to 38.2 [21.6,68.5] pg/mL), while NGAL levels increased (56.2 [47.0,67.0] to 70.9 [52.6,88.0] ng/mL). At one year, both KIM-1 (56.7 [32.0,105.3] pg/mL) and NGAL (77.4 [57.4,96.0] ng/mL) levels remained elevated compared to baseline. Ten individuals who achieved normal weight postoperatively had lower KIM-1 (29.8 [27.1,43.4] vs. 73.3 [39.5,113.6] pg/mL) and NGAL (61.5 [52.3,71.1] vs. 84.0 [59.9,97.3] ng/mL) levels at one year compared to those who remained overweight or obese.

CONCLUSION

Although the kidney functional biomarker, eGFRcr-cyc, did not change, structural injury biomarkers, including KIM-1 and NGAL, increased one year post-SG. These findings underscore the importance of weight management and highlight the necessity for continued, long-term monitoring of kidney function in this patient population to mitigate potential subclinical kidney injury.