'Clinically Negligible' Residual Kidney Function Still Beneficial

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Even at very low levels, residual kidney function in hemodialysis patients clears uremic solutes.
Even at very low levels, residual kidney function in hemodialysis patients clears uremic solutes.
The following article is part of conference coverage from Kidney Week 2017 in New Orleans hosted by the American Society of Nephrology. Renal & Urology News staff will be reporting live on medical studies conducted by nephrologists and other specialists who are tops in their field in acute kidney injury, chronic kidney disease, dialysis, transplantation, and more. Check back for the latest news from Kidney Week 2017.

NEW ORLEANS—Even at very low levels, residual kidney function (RKF) in hemodialysis patients continues to provide clearance of solutes associated with clinical outcomes, researchers concluded in a poster presentation at the American Society of Nephrology's Kidney Week 2017 meeting.

Stephanie M. Toth-Manikowski, MD, a nephrology fellow at Johns Hopkins School of Medicine in Baltimore, and colleagues measured 8 non-urea solutes in plasma from 1280 patients in the HEMO Study 3–6 weeks after randomization. The HEMO Study excluded patients with RKF above 1.5 mL/min/1.73 m2, as a level below was considered “clinically negligible.” The investigators noted that RKF is thought to exert its beneficial effects through improved clearance of uremic toxins, but the level of native kidney function at which this clearance becomes negligible is unknown.

At baseline, 34% of patients had “clinically negligible” RKF (mean 0.7 mL/min/1.73 m2); 66% had no RKF. Patients with RKF were older, had more recent onset of dialysis, and had lower ultrafiltration requirements than patients without RKF.

Compared with patients who had no RKF, those with RKF had significantly lower levels of 7 of the 8 non-urea solutes: nonindoxyl sulfate (-11%), hippurate (-24%), phenylacetylglutamine (-14%), trimethylamine-N-oxide (-7%), methylguanidine (-14%), asymmetric dimethylarginine (-4%), and symmetric dimethylarginine (-7%). The researchers found no reduction in the level of p-cresol sulfate.

The small degree of RKF in these patients was actually much better at decreasing toxin levels than a standard dose of hemodialysis, Dr Toth-Manikowski told Renal & Urology News. “It shows us that even small degrees of residual kidney function, 250 cc of urine a day, is not clinically negligible. It's actually quite metabolically significant,” said Dr Toth-Manikowski, who noted that RKF is known to be associated with improved survival in the hemodialysis population.

“For the nephrologist, the take-home point is that we really should thinking actively about residual kidney function and doing our utmost to preserve it, no matter how small it is,” Dr Toth-Manikowski said.

Nephrologists should start considering novel ways to start patients on dialysis, she said. For example, an HD patient with a certain urea clearance and who makes 500 cc of urine a day may not need the same amount of HD as a patient who has been on HD for 5 years and no longer makes urine, she said.  Another strategy is to keep HD patients on diuretics, she said.

Visit Renal & Urology News' conference section for continuous coverage from Kidney Week 2017.

Reference

Toth-Manikowski SM, Sirich TL, Hostetter TH, et al. HEMO Study results suggest that “clinically negligible” residual kidney function (RKF) is a significant contributor to uremic solute clearance. Data presented in poster format at Kidney Week 2017 in New Orleans (Oct. 31 to Nov. 5). Poster FR-PO894.

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