The role of phagocytic leukocytes following flexible ureterenoscopy, for the treatment of kidney stones: an observational, clinical pilots-study

BACKGROUND: The number of patients undergoing flexible ureterenoscopy (FURS) for the treatment of kidney stones (renal calculi) is increasing annually, and as such the development of post-operative complications, such as acute kidney injury (AKI), haematuria and infection is likely to increase. Phagocytic leukocytes are white blood cells that help fight foreign material such as bacteria and viruses, and they are intrinsically involved in the inflammatory reaction. Investigating the role of phagocytic leukocytes following FURS has not been widely researched. The main aim of the study was to evaluate the role phagocytic leukocytes (neutrophils and monocytes) function, in patients undergoing FURS for the treatment of kidney stones (renal calculi). METHODS: Fourteen consecutive patients aged between 27 and 70 years (median 49.5 years) undergoing FURS for the treatment of kidney stones were recruited (seven males, seven females). Blood samples were collected from each patient at four time points: baseline (pre-operatively) followed by 30, 120 and 240 min post-operatively. Mononuclear (MN) and polymorphonuclear (PMN) leukocyte sub-populations were isolated by density gradient centrifugation techniques. Neutrophil and monocyte cell function was investigated by measuring the cell surface expression of CD62L (L-selectin), CD11b (Mac-1), CD99 and the intracellular production of hydrogen peroxide (H(2)O(2)), via flow cytometry. RESULTS: Significant increases was observed in monocyte CD62L expression post FURS for the treatment of kidney stones (p ≤ 0.05); while significant decreases were observed in neutrophil CD62L. The levels of the other activation markers CD11b, CD99 and H(2)O(2) corresponded to the increases and decreases seen in CD62L for monocytes and neutrophils respectively, though the changes were not statistically significant (p > 0.05). Limiting factors for this study were the relatively small sample size, and restriction on the recruitment time points. CONCLUSIONS: This study demonstrates that following FURS for the treatment of kidney stones, monocytes are rapidly activated and produce potent reactive oxygen intermediates. Interestingly, the pattern of expression in neutrophils suggests that these cells are deactivated in response to the treatment. The leukocyte biomarkers assessed during this investigation may have a role in monitoring the ‘normal’ post-operative response, as no complications occurred in any of the patients; or may help predict potential infectious complications (e.g. urosepsis) that can occur during the post-operative period. This data, however, will need to be validated and reproduced in larger multi-centre studies.