Albuminuria
| Albuminuria | |
|---|---|
| Other names | Proteinuria |
| Specialty | Nephrology |
| Causes | Diabetes (Type 1 & Type 2), Hypertension, Urinary tract infections, Kidney Disease, Certain Medications |
Albuminuria is a pathological condition of elevated albumin protein in the urine (often measured as urine albumin-to-creatinine ratio of >30 milligrams of albumin per 1 gram of creatinine per day).[1] It is a type of proteinuria, and is the most common protein detected on urinalysis that, when elevated, is associated with kidney and cardiovascular disease (CVD). Albumin is an abundant plasma protein (present in blood tissue) which is normally prevented from being lost into the urine by the sieve-like glomeruli of the nephrons. In healthy people, only trace amounts of it are present in urine, but when the filtration system of the kidney is damaged, larger amounts of albumin escape into the urine, which can be quantified and used to determine the extent of kidney injury/kidney disease.[2]
Signs and symptoms
[edit]Albuminuria is often asymptomatic in low quantities but foamy urine may be present. As significant albumin is lost to the urine, swelling of the ankles, hands, belly or face may occur (see edema and nephrotic syndrome). This is because a major role of albumin in the blood is to act as an osmotic agent, keeping water from leaving blood vessels and leaking into the surrounding body tissues.[3]
Causes
[edit]The kidneys normally do not filter large molecules into the urine, so albuminuria can be an indicator of damage to the kidneys or excessive salt intake. It can also occur in patients with long-standing diabetes, especially type 1 diabetes. Recent international guidelines (KDIGO 2024) reclassified chronic kidney disease (CKD) based on cause, glomerular filtration rate category, and albuminuria category (A1, A2, A3).[2]
Causes of albuminuria can be discriminated between by the amount of protein excreted.
- Microalbuminuria (between 30 and 300 mg/24h,[4] mg/L of urine[5] or μg/mg of creatinine[6]) can be a forerunner of diabetic nephropathy. The term albuminuria is now preferred in Nephrology since there is not a "small albumin" (microalbuminuria) or a "big albumin" (macroalbuminuria).[2] A1 represents normal to mildly increased urinary albumin/creatinine ratio (<30 mg/g or < 3 mg/mmol); A2 represents moderately increased urinary albumin/creatinine ratio (30–300 mg/g or 3–30 mg/mmol, previously known as microalbuminuria); and A3 reflects severely increased urinary albumin/creatinine ratio >300 mg/g or > 30 mg/mmol).[2]
Diagnosis
[edit]The amount of protein being lost in the urine can be quantified by collecting the urine for 24 hours, measuring a sample of the pooled urine, and extrapolating to the volume collected.
Alternatively, a urine dipstick test for proteinuria can give a rough estimate of albuminuria. This is because albumin is by far the dominant plasma protein, and bromophenol blue, the reagent used in the dipstick, is specific to albumin.
Treatment
[edit]Though there is some evidence that dietary interventions (to lower red meat intake) can be helpful in lowering albuminuria levels,[7] there is currently no evidence that low protein interventions correlate to improvement in kidney function.[8] Among other measures, blood pressure control, especially with the use of inhibitors of the renin-angiotensin-system, is the most commonly used therapy to control albuminuria.[9]
References
[edit]- ^ "Urine albumin-creatinine ratio (uACR) | National Kidney Foundation". www.kidney.org. Retrieved 2025-03-18.
- ^ a b c d Stevens PE, Ahmed SB, Carrero JJ, Foster B, Francis A, Hall RK, et al. (April 2024). "KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease". Kidney International. 105 (4S): S117 – S314. doi:10.1016/j.kint.2023.10.018. PMID 38490803.
- ^ Levitt DG, Levitt MD (2016). "Human serum albumin homeostasis: a new look at the roles of synthesis, catabolism, renal and gastrointestinal excretion, and the clinical value of serum albumin measurements". International Journal of General Medicine. 9: 229–255. doi:10.2147/ijgm.s102819. PMC 4956071. PMID 27486341.
- ^ Vivian EM (2009). "Endocrine Disorders". In Lee M (ed.). Basic Skills in Interpreting Laboratory Data (fourth ed.). Bethesda, Maryland: American Society of Health-System Pharmacists. pp. 271–318 (291). ISBN 978-1-58528-274-6.
- ^ "Person—microalbumin level (measured)". Australian Institute of Health and Welfare. 1 March 2005.
- ^ Justesen TI, Petersen JL, Ekbom P, Damm P, Mathiesen ER (April 2006). "Albumin-to-creatinine ratio in random urine samples might replace 24-h urine collections in screening for micro- and macroalbuminuria in pregnant woman with type 1 diabetes". Diabetes Care. 29 (4): 924–925. doi:10.2337/diacare.29.04.06.dc06-1555. PMID 16567839.
- ^ de Mello VD, Zelmanovitz T, Perassolo MS, Azevedo MJ, Gross JL (May 2006). "Withdrawal of red meat from the usual diet reduces albuminuria and improves serum fatty acid profile in type 2 diabetes patients with macroalbuminuria". The American Journal of Clinical Nutrition. 83 (5): 1032–1038. doi:10.1093/ajcn/83.5.1032. PMID 16685043.
- ^ Pan Y, Guo LL, Jin HM (September 2008). "Low-protein diet for diabetic nephropathy: a meta-analysis of randomized controlled trials". The American Journal of Clinical Nutrition. 88 (3): 660–666. doi:10.1093/ajcn/88.3.660. PMID 18779281.
- ^ Ksiazek SH, Hu L, Andò S, Pirklbauer M, Säemann MD, Ruotolo C, et al. (April 2024). "Renin-Angiotensin-Aldosterone System: From History to Practice of a Secular Topic". International Journal of Molecular Sciences. 25 (7): 4035. doi:10.3390/ijms25074035. PMC 11012036. PMID 38612843.
