CKDの水分摂取量増加は腎機能を改善せず

慢性腎臓病（CKD）患者の水分摂取量増加に腎機能低下を抑制する効果は認められないと、カナダのグループがJAMA（2018; 319: 1870-1879）に発表した。

　観察研究で、水分摂取量の増加は良好な腎機能と関係することが示唆されている。同グループは、成人CKD患者における水分摂取量増加が腎機能に及ぼす影響を検討した。

　2013～17年にステージ3のCKD〔推算糸球体濾過量（eGFR）30～60mL/分/1.73m2、微量または顕性アルブミン尿〕で、24時間尿量3.0L未満の患者631例を登録。水分摂取量を増やすよう指導する介入群に316例、通常の水分摂取量を維持するよう指導する対照群に315例をランダムに割り付けた。主要評価項目は、登録時から12カ月後までの腎機能（eGFR）の変化とした。

　631例（平均年齢65.0歳、男性63.4％、平均eGFR 43mL/分/1.73m2、尿中アルブミン中央値123mg/dL）のうち、12例（介入群5例、対照群7例）が死亡した。

　1年間追跡できた590例における24時間尿量の平均変化は介入群の方が大きく、対照群に比べ0.6L/日の増加を示した（P＜0.001）。しかし、eGFRの平均変化は介入群が－2.2mL/分/1.73m2、対照群が－1.9mL/分/1.73m2で有意差はなかった（補正群間差－0.3mL/分/1.73m2、P＝0.74）。

Effect of Coaching to Increase Water Intake on Kidney Function Decline in Adults With ChronicKidney Disease: The CKD WIT Randomized Clinical Trial.

Clark WF, Sontrop JM, Huang SH, Gallo K, Moist L, House AA, Cuerden MS, Weir MA, Bagga A, Brimble S, Burke A, Muirhead N, Pandeya S, Garg AX.

JAMA. 2018 May 8;319(18):1870-1879. doi: 10.1001/jama.2018.4930.

Abstract

IMPORTANCE:

In observational studies, increased water intake is associated with better kidney function.

OBJECTIVE:

To determine the effect of coaching to increase water intake on kidney function in adults with chronic kidney disease.

DESIGN, SETTING, AND PARTICIPANTS:

The CKD WIT (Chronic Kidney Disease Water Intake Trial) randomized clinical trial was conducted in 9 centers in Ontario, Canada, from 2013 until 2017 (last day of follow-up, May 25, 2017). Patients had stage 3 chronickidney disease (estimated glomerular filtration rate [eGFR] 30-60 mL/min/1.73 m2 and microalbuminuria or macroalbuminuria) and a 24-hour urine volume of less than 3.0 L.

INTERVENTIONS:

Patients in the hydration group (n = 316) were coached to drink more water, and those in the control group (n = 315) were coached to maintain usual intake.

MAIN OUTCOMES AND MEASURES:

The primary outcome was change in kidney function (eGFR from baseline to 12 months). Secondary outcomes included 1-year change in plasma copeptin concentration, creatinine clearance, 24-hour urine albumin, and patient-reported overall quality of health (0 [worst possible] to 10 [best possible]).

RESULTS:

Of 631 randomized patients (mean age, 65.0 years; men, 63.4%; mean eGFR, 43 mL/min/1.73 m2; median urine albumin, 123 mg/d), 12 died (hydration group [n = 5]; control group [n = 7]). Among 590 survivors with 1-year follow-up measurements (95% of 619), the mean change in 24-hour urine volume was 0.6 L per day higher in the hydration group (95% CI, 0.5 to 0.7; P < .001). The mean change in eGFR was -2.2 mL/min/1.73 m2 in the hydration group and -1.9 mL/min/1.73 m2 in the control group (adjusted between-group difference, -0.3 mL/min/1.73 m2 [95% CI, -1.8 to 1.2; P = .74]). The mean between-group differences (hydration vs control) in secondary outcomes were as follows: plasma copeptin, -2.2 pmol/L (95% CI, -3.9 to -0.5; P = .01); creatinine clearance, 3.6 mL/min/1.73 m2 (95% CI, 0.8 to 6.4; P = .01); urine albumin, 7 mg per day (95% CI, -4 to 51; P = .11); and quality of health, 0.2 points (95% CI, -0.3 to 0.3; P = .22).

CONCLUSIONS AND RELEVANCE:

Among adults with chronic kidney disease, coaching to increase water intake compared with coaching to maintain the same water intake did not significantly slow the decline in kidney function after 1 year. However, the study may have been underpowered to detect a clinically important difference.

TRIAL REGISTRATION:

clinicaltrials.gov Identifier: NCT01766687.

PMID: 29801012 DOI: 10.1001/jama.2018.4930