PROTEINURIA

Definitions of Proteinuria

Urinalysis sticks for ward testing are quite sensitive for proteinuria. They are impregnated with bromocresol green that changes colour in the presence of protein and is used as an indicator dye. They are intended to correlate as follows:

+ with 0.3 g/l, ++ with 1 g/l, +++ with 3 g/l and ++++ with X20 g/l.

False-positive results may be obtained with concentrated or alkaline urine, and false-negative results may be obtained with dilute or markedly acidic urine.

Causes of proteinuria

The protein that is excreted in urine under physiological conditions is not usually detected on urinalysis or dipstick testing. Pathological proteinuria has been classified into four groups: glomerular, tubular, overflow and benign.1

Glomerular proteinuria occurs because of increased glomerular permeability to proteins.

Tubular proteinuria is due to decreased tubular resorption of proteins contained in glomerular filtrate and is seen in tubulo-interstitial diseases.

Overload proteinuria is secondary to increased production, or release, of low-molecular-weight proteins. The myeloproliferative conditions that cause this form of proteinuria are rare in children.

Benign proteinuria implies proteinuria that is detected on urinalysis but

which has no serious underlying pathology. It includes proteinuria seen

in fever or after exercise, idiopathic transient proteinuria, and

orthostatic or postural proteinuria.

Another Classification

Transient proteinuria normal renal function, bland urine sediment, normal blood pressure, absence of significant edema, quantitative protein excretion of usually less than 1g/day; this is not indicative of significant underlying renal disease, and the proteinuria disappears upon repeat testing

Orthostatic proteinuriatall, thin adolescents or adults younger than 30 years (may be associated with severe lordosis); renal function is normal and proteinuria usually is less than 1 g/day; overnight urine collection shows normal protein excretion (ie, < 50 mg during 8-h period)

Persistent proteinuria due to extrarenal diseaseRenal function is normal, urine sediment is bland, blood pressure is normal, significant edema is absent, and quantitative albumin excretion usually is less than 500 mg/day; this is not usually indicative of clinically progressive, underlying renal disease

Persistent proteinuria in excess of 500 mg/dayIs more likely the result of significant glomerular disease

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FUNCTIONAL PROTEINURIA

Functional proteinuria describes a transient increase in urinary protein excretion. The mechanisms responsible for this type of proteinemia are unknown but are probably caused by the changes in glomerular hemodynamics, such as can occur with vigourous excercise or fever. Occurs in the absence of any clear-cut renal or systemic disorder.

Common causes of Functional Proteinuria :

Dehydration Emotional Stress Fever Intense Physical Activity

Most Acute Illness Orthostatic (postural) disorder Organic disease causing functional proteinuria

o Congestive Heart Failureo Hypertensiono Extensive skin lesion (e.g. burns)o High blood concentration of protein (parenteral

administration of albumin or plasma)

Postural or orthostatic proteinuria is a type of functional proteinuria typically seen in <30 years of age. Proteinuria is absent after period of being recumbent, such as after a night sleep, and develops upon rising. Patients with orthostatic proteinuria usually <30 years of age, have moderate proteinemia (excrete < 2g/day of protein), and have normal kidney function.

To diagnose orthostatic proteinuria, split urine specimens are obtained

for comparison. The first morning void is discarded. A 16-hour daytime

specimen is obtained with the patient performing normal activities and

finishing the collection by voiding just before bedtime. An eight-hour

overnight specimen is then collected.

The daytime specimen typically has an increased concentration of

protein, with the nighttime specimen having a normal concentration.

Patients with true glomerular disease have reduced protein excretion

in the supine position, but it will not return to normal (less than 50 mg

per eight hours), as it will with orthostatic proteinuria.

Source :

http://www.hkmacme.org/course/2009BW09-0100/Spotlight%20CS_Sep.pdf http://emedicine.medscape.com/article/238158-overview Adult and pediatric urology Decision Making in Medicine