Abstract
BackgroundPatients with gout frequently have low urinary pH, which is associated with the nephrolithiasis. However, the specific distribution of urinary pH and potential relationship of acidic urine pH to broader manifestations of kidney disease in gout are still poorly understood.MethodsA 2016–2020 population-based cross-sectional study was conducted among 3565 gout patients in the dedicated gout clinic of the Affiliated Hospital of Qingdao University to investigate the association between low urinary pH and kidney disease. We studied patients that we defined to have “primary gout”, based on the absence of > stage 2 CKD. All subjects underwent 14 days of medication washout and 3-day standardized metabolic diet. We obtained general medical information, blood and urine biochemistries, and renal ultrasound examination on the day of the visit. The primary readouts were urine pH, eGFR, nephrolithiasis, renal cysts, microhematuria, and proteinuria. Patients were assigned into 5 subgroups (urine pH ≤5.0, 5.0 <pH≤ 5.5, 5.5 <pH< 6.2, 6.2 ≤pH≤ 6.9, and pH >6.9), aligning with the clinical significance of urine pH.ResultsOverall, the median urine pH and eGFR of all patients was 5.63 (IQR 5.37~6.09), and 98.32 (IQR 86.03~110.6), with acidic urine in 46.5% of patients. The prevalence of nephrolithiasis, microhematuria, and proteinuria were 16.9%, 49.5%, and 6.9%, respectively. By univariate analysis, eGFR was significantly associated with age, sex, duration of gout, tophus, body mass index, systolic blood pressure, diastolic blood pressure, fasting blood glucose, total cholesterol, serum utare, hypertension, diabetes, and urine pH. On multivariable analysis, eGFR was associated with age, sex, diastolic blood pressure, serum uric acid, hypertension, diabetes, and urine pH. Acidic urine pH, especially urine pH < 5.0, was significantly associated with the prevalence of kidney disease, including > stage 1 CKD, nephrolithiasis, kidney cyst, and microhematuria. Patients with 6.2 ≤ urine pH ≤ 6.9 and SU ≤ 480 μmol/L had the highest eGFR with the lowest prevalence of nephrolithiasis, microhematuria, and proteinuria.ConclusionsApproximately half of gout subjects had acidic urine pH. Urine pH < 5.0 was associated with significantly increased nephrolithiasis, renal cyst, microhematuria, and proteinuria. The results support prospective clinical investigation of urinary alkalinization in selected gout patients with acidic urine pH.
Highlights
Patients with gout frequently have low urinary pH, which is associated with the nephrolithiasis
Gout is a highly prevalent disorder [1] that is commonly associated with uric acid and calcium oxalate nephrolithiasis [2], chronic kidney disease (CKD), and elevated risk of CKD progression [3] that appears accelerated in those palpable tophaceous disease [4]
General parameters assessed In this study, of the 11,757 gout patients screened, 3565 patients were selected for analysis (Fig. 1)
Summary
Patients with gout frequently have low urinary pH, which is associated with the nephrolithiasis. Gout is a highly prevalent disorder [1] that is commonly associated with uric acid and calcium oxalate nephrolithiasis [2], chronic kidney disease (CKD), and elevated risk of CKD progression [3] that appears accelerated in those palpable tophaceous disease [4]. Non-ionic forms of urate can promote uric acid and oxalate nephrolithiasis, which are in turn associated with CKD [6, 7]. In gout patients, associated hypertension and type 2 diabetes; hyperuricemia-mediated renal damage; tubular precipitation of urate microcrystals with—in the most severe forms of undertreated tophaceous gout—monosodium urate crystal deposition in the medulla; and toxic effects of analgesics used to treat gout flares [8, 9] are among the mechanisms that could contribute to CKD progression. Due to lack of hard clinical research evidence, the 2020 American College of Rheumatology (ACR) guidelines for management of gout did not recommend alkalization of urine pH in patients with gout [20]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
