Can an elevated urine albumin-to-creatinine ratio indicate kidney injury even with preserved filtration markers?

An elevated urine albumin-to-creatinine ratio (UACR) can identify abnormal glomerular albumin leakage before filtration-based measures such as eGFR decline. For a 71-year-old man, this is clinically relevant because preserved filtration does not rule out early kidney damage.

Clinical evidence

• Persistent albuminuria is an established marker of kidney damage. KDIGO recognizes an ACR of ≥30 mg/g, persistent for at least 3 months, as evidence of chronic kidney damage even when eGFR is ≥60 mL/min/1.73 m².
• UACR and eGFR capture different processes: UACR reflects albumin leakage into urine, whereas eGFR reflects overall filtration. Structural injury or compensatory hyperfiltration can therefore coexist with apparently preserved filtration markers.
• A single elevated UACR is not sufficient to establish chronic kidney disease or a specific renal diagnosis. Confirmation—preferably with a repeat first-morning midstream urine specimen—and demonstration of persistence are important.

Mechanistic interpretation

• Albumin normally traverses the glomerular filtration barrier only minimally. Injury or dysfunction involving glomerular endothelial cells, the glomerular basement membrane, or podocytes can increase urinary albumin loss.
• Renal microvascular/endothelial dysfunction is a biologically credible contributor because the glomerular endothelium is part of this barrier. However, UACR does not distinguish endothelial injury from podocyte or basement-membrane abnormalities, nor does it prove a particular microscopic lesion.

Clinical implications

• Persistent UACR elevation with preserved eGFR should be treated as a meaningful renal signal rather than dismissed as “normal kidney function.”
• Interpretation requires clinical context, since transient elevations can occur and albuminuria is not specific for one cause or one anatomic lesion.

Bottom line

• Persistent UACR elevation can indicate glomerular barrier injury—and plausibly renal microvascular injury—even when filtration markers remain preserved; it is clinically important but nonspecific and requires repeat confirmation and contextual evaluation.