Microscopic hematuria is one of the most common presentations of IgA nephropathy (IgAN), yet it remains underused in disease assessment compared with proteinuria and eGFR. Persistent or time-averaged hematuria has been associated with faster eGFR decline and poorer kidney outcomes, and a meta-analysis of 13 studies involving 5,660 patients found that microscopic hematuria at biopsy or disease onset was associated with an 87% higher risk of kidney failure (RR, 1.87; 95% CI, 1.40–2.50). Hematuria may also reflect active glomerular inflammation: immune-complex deposition and complement activation can disrupt the filtration barrier, allowing red blood cells to enter the urine. Because bleeding can arise from nonglomerular causes, clinicians should interpret hematuria alongside proteinuria, kidney function, clinical history, and findings such as dysmorphic red blood cells (RBCs) or RBC casts.
Serial assessment may provide additional insight into both disease activity and treatment response. Studies suggest that hematuria remission is associated with better kidney outcomes, while persistence may identify patients who need closer monitoring or further evaluation. Recent trials of targeted IgAN therapies have also reported reductions in microscopic hematuria, supporting its potential as a treatment-sensitive marker of glomerular inflammation. However, prospective studies are still needed before hematuria can routinely guide therapeutic decisions. Practical limitations remain, including day-to-day variability, inconsistent definitions, and preanalytic factors affecting urinalysis. For now, the authors advocate moving beyond a proteinuria-centric approach by incorporating hematuria or hemoglobinuria monitoring alongside proteinuria and eGFR when assessing IgAN activity and progression.
Reference: Floege J, Fervenza FC, Coppo R. Microscopic hematuria in IgA nephropathy: a biomarker of disease activity. Clin Kidney J. 2026 Jan 12;19(2):sfag003. doi: 10.1093/ckj/sfag003. PMID: 41704425; PMCID: PMC12907559.
