Association Between Urine pH and Kidney Outcomes in Patients with Biopsy-Proven Kidney Disease

Background/Objectives: Lower urine pH has been associated with reduced kidney function and increased risk of kidney disease, but its prognostic and pathological significance in biopsy-proven kidney disease remains unclear. Medullary cast formation has been shown to predict adverse renal outcomes beyond cortical interstitial fibrosis and tubular atrophy (IFTA), although its clinical determinants are not fully understood. We examined the associations of urine pH with kidney outcomes and medullary cast formation in patients undergoing native kidney biopsy.

Methods

Among 1167 adults who underwent native kidney biopsy between 2011 and 2024, 503 patients with evaluable medullary tissue were included. Urine pH was analyzed in relation to clinical and histological variables and kidney outcomes. The primary outcome was a ≥40% decline in estimated glomerular filtration rate (eGFR) or initiation of renal replacement therapy.