Urine-to-Plasma Urea Ratio: Disentangling Tubular Concentrating Ability From GFR

he kidney tubules make up the vast majority of the kidney’s cortical structure, expend most of the energy used by the kidneys, and play a central role in a variety of essential biological functions. However, chronic kidney disease (CKD) diagnosis, staging, and prognosis remain anchored to estimated glomerular ﬁltration rate (eGFR) and albuminuria, which primarily reﬂect glomerular health and do not fully capture tubular pathology. 1 Biopsy-proven interstitial ﬁbrosis and tubular atrophy is found in nearly all forms of CKD