Albuminuria and heart failure: what it may reveal

What is albuminuria, and how is it measured?

Albuminuria means that urine contains more albumin than expected. Under normal conditions, the kidney filtration barrier prevents significant amounts of this blood protein from entering the urine; an increase may reflect glomerular, microvascular, or hemodynamic changes, but it does not identify the cause by itself^1,2,3. The preferred test is the urine albumin-to-creatinine ratio, or UACR. It reduces the effect of urine concentration or dilution and can be measured in a single urine sample, so a 24-hour collection is not routinely required¹. KDIGO classifies UACR as A1, below 30 mg/g, normal to mildly increased; A2, 30–299 mg/g, moderately increased; and A3, 300 mg/g or higher, severely increased. Although the terms “microalbuminuria” and “macroalbuminuria” still appear in research, the A1, A2, and A3 categories are now preferred^1,4.

What can urine albumin reveal about the heart?

Albuminuria can be a marker of shared vulnerability involving the kidneys, blood vessels, and heart. Its relationship with heart failure is bidirectional: increased urine albumin may precede heart failure as a sign of kidney or vascular injury, while established heart failure can also raise urine albumin, particularly when elevated venous pressure causes kidney congestion^2,3. Proposed mechanisms include endothelial and microvascular dysfunction, injury to the glomerular barrier, systemic inflammation, oxidative stress, activation of the renin-angiotensin-aldosterone system, and sodium and water retention. These mechanisms may explain the association, but they do not prove that urine albumin directly causes heart failure^2,3. UACR can also be elevated when estimated glomerular filtration rate, or eGFR, remains preserved: UACR measures albumin loss, whereas eGFR estimates filtration capacity. In clinical practice, both measurements are interpreted together to obtain a more complete picture of cardiovascular, kidney, and metabolic risk [1,3-5].

How strongly is albuminuria associated with heart failure?

Higher albuminuria is progressively associated with more heart failure and other cardiovascular events, but it is a risk marker rather than an individual prediction. A meta-analysis of 27,503,140 people from 114 cohorts, with albuminuria data available for approximately 9.1 million, found that the association persisted after adjustment for blood pressure, diabetes, smoking, cholesterol, and previous cardiovascular disease⁵. Among participants with an eGFR of 90–104 mL/min/1.73 m², compared with a UACR below 10 mg/g, the rounded adjusted hazard ratios (HRs) for heart failure were 1.3 for a UACR of 10–29 mg/g, 1.4 for 30–299 mg/g, and 2.5 for 300 mg/g or higher⁵. In the HOPE study, greater urinary albumin excretion was progressively associated with cardiovascular events, death, and hospitalization for heart failure, including at levels below traditional thresholds, reinforcing that risk occurs along a continuum⁶. Among people with established heart failure, reviews describe albuminuria as a common finding related to both comorbidities and congestion³. In the CHARM program, albuminuria was common and associated with a worse prognosis, although the result must be interpreted within each patient’s clinical context⁷. In the GISSI-HF study, elevated urinary albumin excretion also had prognostic value, but factors such as congestion, diabetes, blood pressure, kidney function, and timing of urine collection influence its interpretation⁸.

How should an elevated UACR be confirmed?

An elevated UACR should be confirmed before it is considered a persistent abnormality. A first-morning urine sample is preferred because it has less variability and correlates better with daily albumin excretion, although a random sample is acceptable when morning collection is impractical¹. Positive results, particularly those close to 30 mg/g or found in someone without known risk factors, usually need to be repeated under appropriate conditions. Recent exercise, symptomatic urinary tract infection, menstruation, blood in the urine, differences in creatinine excretion, and changes in urine concentration can temporarily affect UACR¹. Standard urine dipsticks may miss small but clinically relevant amounts of albumin, while a positive dipstick result should be confirmed with a quantitative laboratory method, preferably UACR¹. A UACR of 30 mg/g or higher is a marker of kidney damage, but chronic kidney disease requires evidence that the kidney abnormality has persisted for at least three months. One abnormal result is not enough to make the diagnosis^1,4.

Who should discuss UACR testing with a clinician?

People with high blood pressure, diabetes, obesity, smoking exposure, kidney disease, cardiovascular disease, or heart failure are more likely to benefit from UACR assessment. For people with risk factors but no established chronic kidney disease, the Brazilian clinical protocol recommends annual follow-up with eGFR, UACR, and urinalysis⁴. Checking creatinine alone may miss albuminuria in someone with preserved filtration, although universal UACR screening for every person with heart failure is not yet consistently recommended across heart-failure-specific guidelines [1-3,6]. Persistent values of 30 mg/g or higher require clinical assessment, while results of 300 mg/g or higher indicate more severe albuminuria and greater cardiorenal risk. Urgency nevertheless depends on symptoms, eGFR, other medical conditions, and how quickly the result has changed^1,4,5. A clinical review may include repeat UACR, blood creatinine and eGFR, blood pressure, diabetes control, blood or signs of infection in the urine, current medications, swelling, breathlessness, and kidney and cardiovascular history. Blood pressure, glucose, cholesterol, body weight, smoking, and lifestyle should be addressed together [1-3]. Significant breathlessness, rapidly worsening swelling, or other signs of congestion warrant prompt medical assessment.

What are the most common questions about albuminuria?

A single albuminuria result does not confirm either chronic kidney disease or heart failure. “Does an elevated UACR mean I will develop heart failure?” No; it indicates a statistical association with higher risk and must be interpreted alongside symptoms, blood pressure, diabetes, kidney function, and medical history. “Does normal creatinine rule it out?” No; UACR may be elevated even when eGFR is preserved^1,5,2. “Do I need a 24-hour urine collection?” Usually not; a single sample, preferably the first urine of the morning, is generally suitable for UACR testing¹. “Can I wait before repeating the test?” Repeat testing is often necessary, but timing should be individualized, particularly when UACR is very high, symptoms are present, or kidney function is worsening. Travelers, expatriates, and crew members spending only a short time in Santos should keep the complete laboratory report and arrange follow-up with a clinician who can compare results over time. This content is for information and education only and does not replace an individual medical consultation. References:¹ Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International. 2024;105(4S):S117–S314. DOI: https://doi.org/10.1016/j.kint.2023.10.018⁴ Brazilian Ministry of Health. Protocolo Clínico e Diretrizes Terapêuticas da Doença Renal Crônica. Brasília: Ministry of Health; 2024. URL: https://www.gov.br/saude/pt-br/assuntos/pcdt/d/doenca-renal-cronica⁹ American Diabetes Association Professional Practice Committee. 11. Chronic Kidney Disease and Risk Management: Standards of Care in Diabetes—2024. Diabetes Care. 2024;47(Suppl 1):S219–S230. DOI: https://doi.org/10.2337/dc24-S011⁵ Grams ME, Coresh J, Matsushita K, et al.; CKD Prognosis Consortium. Estimated Glomerular Filtration Rate, Albuminuria, and Adverse Outcomes: An Individual-Participant Data Meta-Analysis. JAMA. 2023;330(13):1266–1277. DOI: https://doi.org/10.1001/jama.2023.17002² Khan MS, Shahid I, Bennis A, et al. Albuminuria: An Underappreciated Risk Factor for Cardiovascular Disease. Journal of the American College of Cardiology. 2023;82(22):2126–2144. DOI: https://doi.org/10.1016/j.jacc.2023.09.005³ Mullens W, Damman K, Testani JM, et al. Evaluation of Kidney Function Throughout the Heart Failure Trajectory—A Position Statement From the Heart Failure Association of the European Society of Cardiology. European Journal of Heart Failure. 2020;22(4):584–603. DOI: https://doi.org/10.1002/ejhf.1697⁷ Jackson CE, Solomon SD, Gerstein HC, et al. Albuminuria in Chronic Heart Failure: Prevalence and Prognostic Importance. The Lancet. 2009;374(9689):543–550. DOI: https://doi.org/10.1016/S0140-6736(09)61378-7⁶ Gerstein HC, Mann JFE, Yi Q, et al. Albuminuria and Risk of Cardiovascular Events, Death, and Heart Failure in Diabetic and Nondiabetic Individuals. JAMA. 2001;286(4):421–426. DOI: https://doi.org/10.1001/jama.286.4.421⁸ Masson S, Latini R, Milani V, et al. Prevalence and Prognostic Value of Elevated Urinary Albumin Excretion in Patients With Chronic Heart Failure: Data From the GISSI-Heart Failure Trial. Circulation: Heart Failure. 2010;3(1):65–72. DOI: https://doi.org/10.1161/CIRCHEARTFAILURE.109.881805