RAASi Therapy Attenuates the Association between 24-h Urinary Potassium Excretion and Dietary Potassium Intake in CKD Patients

Abstract

The aim of this study was to evaluate urinary potassium (K) excretion as a reliable marker of dietary K intake, in a cohort of CKD patients with or without Renin-Angiotensin-Aldosterone System (RAAS) inhibitor therapy. One hundred and thirty-eight consecutive out-patients (51 f and 87 m) aged 60 ± 13 years and affected by CKD stage 3–4, who were metabolically and nutritionally stable, entered the study between November 2021 and October 2022. No difference was observed between patients with (n = 85) or without (n = 53) RAAS inhibitor therapy, regarding dietary intakes, blood biochemistry, and 24-h urine excretion parameters. Considering all patients, urinary K showed a weak relationship with eGFR (r = 0.243, p < 0.01), and with dietary K intake (r = 0.184, p < 0.05). Serum K was not associated with dietary K intake, but an inverse relationship was observed with eGFR (r = −0.269, p < 0.01). When patients were examined depending on whether they were receiving RAAS inhibitor therapy, the weak inverse relationship between serum K and eGFR was maintained in both groups. Conversely, urinary K excretion remained positively associated with dietary K intake only in the no RAAS inhibitor group. In conclusion, 24-h urine K excretion may be used as a surrogate of K intake, but RAAS inhibitor therapy reduces the association between 24-h urine K excretion and dietary K intake in CKD patients.

Potassium Intake and Human Health

“…Notably, guidelines on CKD management [ 19 ] highlight the role of dietary potassium intake in CKD, recommending the assessment of dietary potassium intake in CKD patients, particularly those with potential hyperkalaemia [ 20 ]. In this context, two other studies included in this Special Issue explored different aspects of the assessment of dietary potassium intake in patients with CKD [ 21 , 22 ]. Moreover, since the mechanisms of potassium homeostasis and excretion are impaired in these individuals, 24 h urine collection (the recognised gold standard for monitoring potassium intake [ 23 ]) may not be reliable to evaluate potassium intake in this setting.…”

“…In particular, one study evaluated the relationship between urinary potassium excretion (via 24 h urine collection) and dietary potassium intake (via a questionnaire) in a cohort of stage 3–4 CKD patients with or without RAAS inhibitor therapy [ 21 ]. The main analysis, which included 138 patients (60 ± 13 years), indicated that urinary potassium excretion was significantly, but weakly, associated with the glomerular filtration rate and dietary potassium intake.…”