Albuminuria

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Albuminuria
Classification and external resources
ICD-10 R80
ICD-9-CM 791.0
MeSH D000419

Albuminuria is a pathological condition wherein the protein albumin is abnormally present in the urine. It is a type of proteinuria. Albumin is one type of plasma protein found in the urine in normal subjects and in larger quantity in patients with kidney disease. For a number of reasons, clinical terminology is changing to focus on albuminuria rather than proteinuria.[1]

Symptoms[edit]

It is usually asymptomatic but whitish foam may appear in urine. Swelling of the ankles, hands, belly or the face may occur if losses of albumin are important and produce low serum protein levels (nephrotic syndrome).

Measurement[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.

Also 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 bromphenol blue the agent used in the dipstick is specific to albumin.

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 2012) reclassified chronic kidney disease (CKD) based on cause, glomerular filtration rate category, and albuminuria category (A1,A2,A3).[1]

Causes of albuminuria can be discriminated between by the amount of protein excreted.

  • The nephrotic syndrome usually results in the excretion of about 3.0 to 3.5 grams per 24 hours.[medical citation needed]
  • Nephritic syndrome results in far less albuminuria.[medical citation needed]
  • Microalbuminuria (between 30 and 300 mg/24h,[2] mg/l of urine[3] or µg/mg of creatinine[4]) 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).[5] A1 represents normal to mildly increased urinary albumin/creatinine ratio (<30 mg/g or < 3 mg/mmmol); A2 represents moderately increased urinary albumin/creatinine ratio (30–300 mg/g or 3–30 mg/mmmol, previously known as microalbuminuria); and A3 reflects severely increased urinary albumin/creatinine ratio >300 mg/g or > 30 mg/mmol).[1]

Treatment.[edit]

Though there is some evidence that dietary interventions (to lower red meat intake) can be helpful in lowering albuminuria levels,[6] there is currently no evidence that low protein interventions correlate to improvement in kidney function.[7] Among other measures, blood pressure control, specially with the use of inhibitors of the renin-angiotensin-system, are the most common used therapies to control albuminuria.

References[edit]

  1. ^ a b c KDIGO (Kidney Disease Improving Global Outcomes (2013). "KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease" (PDF). Kidney International Supplement. 3 (1): 1–150. Retrieved 5 February 2016. 
  2. ^ Page 291 in: Basic Skills in Interpreting Laboratory Data. ISBN 978-1-58528-180-0. Retrieved 23 May 2013. 
  3. ^ Person—microalbumin level (measured) at Australian Institute of Health and Welfare. 01/03/2005
  4. ^ [1] Justesen, T.; Petersen, J.; Ekbom, P.; Damm, P.; Mathiesen, E. (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. 
  5. ^ KDIGO 2012. "Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease" (PDF). 
  6. ^ de Mello, V. D. F. et al. "Withdrawal of red meat from the usual diet reduces albuminuria and improves serum fatty acid profile in type 2 diabetes patients with macroalbuminuria." American Journal of Clinical Nutrition 83.5 (2006): 1032.
  7. ^ Pan Yu et al. "Low-protein diet for diabetic nephropathy: a meta-analysis of randomized controlled trials." American Journal of Clinical Nutrition 88 (2008): 660-666.