Urine Analysis: Part 14 – Urine protein 24 hours sample, Classification of Proteinuria
- Collect a random sample of urine to rule out the presence of protein.
- 24 hours of urine is collected in a sterile container.
- Discard the first sample then collect all other samples for 24 hours.
- Add the last sample in the container.
- Add a few ml of HCL into the container.
- Also, refrigerate the sample during collection.
- Centrifuge and adjust to pH 7.0.
- Analyze a fresh sample.
- Avoid dehydration due to the lake of fluid intake.
- Avoid the contamination of urine from the vaginal secretions.
- Not adequate collection during urinary tract infections (UTI).
- Use of contrast media in radiology within the last three days.
- Avoid strenuous exercise.
- Avoid emotional stress.
- The presence of protein in urine is an indicator of renal diseases.
- This may be done to evaluate the edema.
- Proteins are found in:
- Amniotic fluid.
- In a healthy individual with normal renal function, there will be no proteins in the urine or may find only traces.
- Urine protein sources are:
- From the blood.
- From kidneys.
- From the urinary tract.
- From vagina and prostate.
Classification of the proteinuria on the basis of the amount of protein excreted in the urine:
|Type proteinuria on the basis of the amount||Amount of the protein
|Minimal proteinuria||<0.5 mg/24 hours of urine||It may be due to:
|Moderate proteinuria||0.5 to 3 g/24 hours of urine||It may be seen in:
|Marked or severe proteinuria
||>3 g/24 hours of urine||It is seen in:
Mechanism of protein in the urine:
- Urine is formed by the ultrafiltration of plasma across the glomeruli.
- Plasma protein with molecular weight >40,000 is retained in the plasma.
- Normally glomerular membrane does not allow filtration of protein into the urine because of narrow spaces in the glomerular membrane.
- In glomerulonephritis, the glomerular membrane is injured and there are larger spaces from where the protein particularly albumin (smaller in size) can easily pass in the urine.
- Albumin is 1/3 of the urinary protein.
- Albumin filtered through glomeruli very easily in comparison to plasma globulin.
- In pathologic conditions Albumin is abundant.
- Urine Albumin is used as the protein marker of glomerular permeability.
- The term proteinuria is often used synonymously for Albuminuria.
- Protein is the single most important parameter for renal dysfunction.
- If more than a trace of protein found in urine then advise 24 hours urinary protein.
- 1 to 14 mg/dL
- At rest = 50 to 80 mg/day
- After intense excercise = <250 mg/day
- The normal albumin excretion rate is <20 µg/minutes.
- Or <30 mg/day
- Adult male = 10 to 140 mg /L OR = 1 to 14 mg/dL
- Adult female = 30 to 100 mg/L OR 3 to 10 mg/dL
- Child < 10 years = 10 to 100 mg/L OR 1 to 10 mg/dL.
- < 150 mg/24 hours.
- Qualitative = normally negative.
- Significant proteinuria is > 300 mg / 24 hours.
- Usually, 24 hours urine sample is needed.
- Urine protein assays are sensitive to all types of proteins like albumin, globulins, and Bence-Jones protein.
- Most of the assay can detect a minimum of 3 mg/dL of protein in the urine.
- Urine dipstick is most commonly used. This is most sensitive to albumin.
- The dipstick can detect albumin when it is about 18 mg/dL
Increased proteinuria is seen in:
- Glomerular diseases :
- Acute and chronic glomerulonephritis.
- Nephrotic syndrome.
- Polycystic kidney
- Autoimmune diseases like SLE.
- Diabetes mellitus.
- Malignant hypertension.
- Decreased tubular reabsorption :
- Acute and chronic pyelonephritis.
- Renal tubular diseases.
- Wilson’s disease.
- Fanconi’s syndrome.
- Interstitial nephritis.
- Other causes are :
- Congestive heart failure.
- Multiple Myeloma.
- Malignant Lymphoma.
- Waldenstrom’s macroglobulinemia.
- Trauma and stress.
- Acute infections like septicemia.
- Toxemia of pregnancy.
- Poisoning from phosphorus, gold, mercury, lead, and phenol.
- Drugs like opiates and etc.
- Postural proteinuria.